Chevrolet - Chevy Trucks - Workshop Manual - 1997 - 1997

MOTOR HOME GUI FOREWORD This manual has been developed to provide the owner and operator with service information for the Chevrolet motor home chassis. Major components and systems are described and maintenance and inspection procedures are given . In addition to providing information for proper maintenance of the motor home chassis, some inspection and diagnosis procedures are included to help detect and identify common .problem conditions which may occur. In a section at the end of this manual are appendixes containing additional information helpful in maintaining the motor home. This includes information on drive belts, storage of the motor home, identification for nuts and bolts, and formulas for converting to metric measurements . The organization of the Chevrolet Motor Home Chassis Service Guide is similar to that of the Chevrolet Light-Duty Truck 10-30 Series Shop Manual . While the information contained in this Service Guide is intended to establish proper maintenance and inspection procedures, there may be times when more detailed diagnostic and repair procedures contained in the Shop Manual may be required . The similarity in organization can make reference to the Shop Manual easier. Specific references to Chevrolet Service Bulletins have been included within the text and appendixes of various sections of this manual . Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer." They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information . SUGGESTIONS FOR IMPROVED SERVICE Motor homes can only service the needs of their owners when they are in dependable operating condition and able to perform properly . Costly breakdowns, service calls and downtime expense can be minimized through properly performed regular maintenance. Therefore, you should become familiar with Chevrolet's maintenance recommendations which have been developed in the interest of maximum vehicle performance and economical operation by those best qualified . These recommendations are outlined in the General Motors Maintenance Schedule for Light-Duty Trucks which was furnished with your Chevrolet chassis . WHEN TRAVELING, CHEVROLET RECOMMENDS THE FOLLOWING TO OBTAIN SERVICE : 1 . Wherever you are traveling, look in the yellow pages to see if there is a local Chevrolet dealership . Call the local dealership and ask to talk to the service manager. Tell him, as specifically as possible, the nature of your problem(s) . Often, even a small dealership with limited facilities will be able to perform some of the simpler tasks of a lube or oil filter change, or other minor repairs. If the local dealer is not able to assist you, he may know of reputable towing companies, neighboring Chevrolet dealerships and independent repair facilities who may be able to help. Often the Chevrolet dealer may assist a warranty situation via a sublet through a local repair shop if the local Chevrolet dealer's shop cannot handle the necessary repairs . 2 . If information is provided, motor home owners might call the RV manufacturer's service department. Based on prior positive experiences, the service department may be able to provide suggestions on where to take the vehicle, in that local area, for good repair work ; i.e., the RV manufacturer's nearest local coach dealer, Chevrolet dealers, or even independent repair facilities with a history of proper and competent repair experience on the motor home . 3. Or the motor home owner may need to contact the Chevrolet Customer Assistance Center 1-800 FOR CHEV or (1-800-222-1020). When calling, be as specific as possible regarding the nature of the problem. Ask for the name and telephone number of the nearest dealer who has a demonstrated interest and the facilities for repairing motor coaches. Remember to ask for the name of that dealership's service manager so that you may call him directly to determine if he is able and available to handle your particular motor home service needs. 4. 24 hour road side assistance Call 1-800 CHEV USA Canada 1-800 268 6800 roadside 1-800 263 3777 customer assistance TABLE OF CONTENTS SECTION 1 - INTRODUCTION . . . . . . . . . . . . 1-1 General Information . . . . . . . . . . . . . . . . . . . 1-1 G-Series Motor Home Chassis . . . . . . . . . . 1-1 P-Series Motor Home Chassis . . . . . 1-1, 1-1AB Identification Numbers . . . . . . . . . . . . . . . . 1-1 Vehicle Identification Number (VIN) . . . . 1-2 Service Parts Identification Label . . . . . . 1-3 Motor Home Towing . . . . . . . . . . . . . . . . . . . 1-3 Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 Recommended Fluids and Lubricants . . 1-4 Lubricant Capacities . . . . . . . . . . . . . . . . 1-5 Lubrication Points - G-Series . . . . . . . . 1-6 Lubrication Points - P-Series . . . . . . . . . 1-6 Lubrication Points - I-Beam Axle . . . . . . 1-7 SECTION 2 - HEATING AND AIR CONDITIONING . . . . . . . . Heating System . . . . . . . . . . . . . . . . . . . . . . General Description . . . . . . . . . . . . . . . . . Troubleshooting the System . . . . . . . . . . Air Conditioning System . . . . . . . . . . . . . . . General Description '. . . . . . . . . . . . . . . . . Receiver-Dehydrator . . . . . . . . . . . . . . . Accumulator . . . . . . . . . . . . . . . . . . . . . G-Series System . . . . . . . . . . . . . . . . . . . . P-Series System . . . . . . . . . . . . . . . . . . . . Maintenance and Inspection . . . . . . . . . . Refrigeration Section . . . . . . . . . . . . . . Inspection . . . . . . . . . . . . . . . . . . . . . . . Operational Quick Checks . . . . . . . . . . Air Distribution Section . . . . . . . . . . . . . . . . Electrical Circuit Diagnosis . . . . . . . . . . . Vacuum System Diagnosis (G-Series) . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix 2-1 - Optional Air Conditioning System . . . . . . . . . . . . . . . . 2-1 2-1 2-1 2-1 2-2 2-2 . 2-2 2-2 2-22-4 2-4 2-4 2-4 2-4 2-5 2-5 2-5 2-6 SECTION 3 - STEERING, SUSPENSION, WHEELS AND TIRES . . . . . . . . 3-1 Front Alignment . . .. . . . . . . . . . . . . . . . . . . . 3-1 General Description . . . . . . . . . . . . . . . . . 3-1 Caster . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 Camber . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 Toe-In . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 Maintenance and Inspection . . . . . . . . . . 3-2 Alignment Check . . . . . . . . .. . . . . . . . . 3-2 Frame Angle Measurement . . . . . . . . . 3-3 Lower Ball Joint Inspection . . . . . . . . . 3-3 Steering System . . . . . . . . . . . . . . . . . . . . . . 3-4 Steering Linkage . . . . . . . . . .. . . . . . . . . . . 3-4 General Description . . . . . . . . . . . . . . . 3-4 Maintenance and Inspection . . . . . . . . 3-4 Lubrication of Steering Linkage . . . . 3-4 Steering Linkage Support Assemblies (P-Series) . . . . . . . . . . . . . . . . . . . . . . 3-4 Steering Damper Check . . . . . . . . . . 3-4 Power Steering System . . . . . . . . . . . . . . 3-5 General Description . . . . . . . . . . . . . . . 3-5 Maintenance and Inspection . . . . . . . . 3-5 Hard Steering at Engine Idle . . . . . . 3-6 Leakage Check . . . . . . . . . . . . . . . . . 3-6 Quick Fixes . . . . . . . . . . . . . 3-7 Pump Belt Tension Adjustment .. . . . .. .. . 3-7 Suspension System . . . . . . . . . . . . . . . . . . . 3-8 Front Suspension . . . . . . . . . . . . . . . . . . . 3-8 General Description . . . . . . . . . . . . . . . 3-8 Maintenance and Inspection . . . . . . . . 3-8 Wheel Bearing Lubrication . . . . . . . . 3-8 Wheel Bearing Adjustment Check . . . . .. . . . . . . . . . 3-8 Wheel Bearing Adjustment . . . . . . . 3-8 Air Bag Cylinder Inspection . . . . . . . 3-9 Vehicle Ride Height - Front Coil Spring/Air Bag Replacement . . . . . . 3-9 Shock Absorber Diagnosis . . . . . . . 3-10 Rear Suspension . . . . . . . . . . . . . . . . . . 3-12 General Description . . . . . . . . . . . . . . 3-12 Maintenance and Inspection . . . . . . . 3-12 Wheels and Tires . . . . . . . . . . . . . . . . . . . . 3-13 General Description . . . . . . . . . . . . . . . . 3-13 Maintenance and Inspection . . . . . . . . . 3-13 Tire Inspection and Rotation . . . . . . . 3-13 Inflation Pressure . . . . . . . . . . . . . . . . 3-13 Determining Wheel/Tire Loads . . . . . 3-13 Wheel and Tire Balancing . . . . . . . . . 3-14 Tire Replacement . . . . . . . . . . . . . . . . 3-13 Wheel/Stud Bolt Replacement . . . . . . 3-16 Typical Wheel and Stud Bolt Failures . . . . . . . . . . . . . . . . 3-16 WornlBroken Stud Bolts . . . . . . . . . 3-16 Worn/Cracked Wheels . . . . . . . . . . 3-16 Bent Rim Check/Tire to Rim Matching . . . . . . . . . . . . . . . . . . . 3-17 TIRE Wear - Tire Rotation . . . . . . . 3-18 Effect of Inflation . . . . . . . . . . . . . . 3-18 Effect of Overloading . . . . . . . . . . . 3-18 Effect of Overheating . . . . . . . . . . . 3-18 Appendix 3-1 - Steering Relay and Tie Rod Parts Identification . 3-20 Appendix 3-2 - Typical Load Height Curves . . . . . . . . . . . . . . . 3-21 SECTION 4 - PROPELLER SHAFTS AND UNIVERSAL JOINTS . . . . . . . . General Description . . . . . . . . . . . . . . . . . . . Propeller Shafts . . . . . . . . . . . . . . . . . . . . Universal Joints . . . . . . . . . . . . . . . . . . . . Maintenance and Inspection . . . . . . . . . . . . Typical Failures . . . . . . . . . . . . . . . . . . . . Driveline Noise and/or Vibration Checks . Driveline Balance Procedure . . . . . . . . . . Table - 1 4-1 4-1 4-1 4-1 4-2 4-2 4-3 4-3 TABLE OF CONTENTS (Cont'd) Appendix 4-1 - Driveline Vibrations Appendix 4-1 - One and Two Drive Shaft Systems . . . . . . . . . . . . . . . 4-6 Appendix 4-2 - Driveline Vibrations Three-Shaft Drivelines . . . . 4-8 SECTION 5 - REAR AXLE . . . . . . . . . . . . . . . General Description . . . . . . . . . . . . . . . . . . . Maintenance and Inspection . . . . . . . . . . . . Differential Fluid . . . . . . . . . . . . . . . . . . . . Wheel Bearing Adjustment (Tapered Bearing) . . . . . . . . . . . . . . . . . . . Wheel Bearing Adjustment (Barrel-Type Bearing) . . . . . . . . . . . . . . . . Axle Housing . . . . . . . . . . . . . . . . . . . . . . Bent Axle Housing . . . . . . . . . . . . . . . . . . 5-1 5-1 5-1 5-1 5-1 5-2 5-3 5-3 SECTION 6 - BRAKES . . . . . . . . . . . . . . . . . . 6-1 General Description . . . . . . . . . . . . . . . . . . . 6-1 Disc Brakes . . . . . . . . . . . . . . . . . . . . . . . . 6-2 Drum Brakes . . . . . . . . . . . . . . . . . . . . . . . 6-3 Power Units . . . . . . . . . . . . . . . . . . . . . . . . 6-3 Parking Brake(s) . . . . . . . . . . . . . . . . . . . . 6-4 Maintenance and Inspection . . . . . . . . . . . . 6-5 Filling the Master Cylinder . . . . . . . . . . . . 6-5 Pedal Travel Check . . . . . . . . . . . . . . . . . . 6-5 Brake Hose Inspection . . . . . . . . . . . . . . . 6-5 Lining Inspection . . . . . . . . . . . . . . . . . . . 6-5 Brake Drum Inspection . . . . . . . . . . . . . . 6-5 Brake Rotor Inspection . . . . . . . . . . . . . . 6-6 Disc Brake Squeal or Squeak . . . . . . . . . . 6-6 Brake Caliper Noise . . . . . . . . . . . 6-6 Brake Pedal/Stoplight Adjustment . . . . . . 6-6 Bleeding Brake Hydraulic System . . . . . . 6-7 Bleeding Hydro-Boost Brake System . . . 6-8 Power Brake Units . . . . . . . . . . . . . . . . . . 6-8 Parking Brake . . . . . . . . . . . . . . . . . . . . . . 6-8 Inspection . . . . . . . . . . . . . . . . . . . . . . . 6-8 Drum Balance . . . . . . . . . . . . . . . . . . . . . 6-9 Cable Adjustment . . . . . . . . . . . . . . . . . 6-9 Foot Pedal Type (G-Series) . . . . . . . . . . 6-9 Orcheln Lever Type (P-Series) . . . . . . . 6-9 Propeller Shaft Drum-Type Brake Adjustment (Drum On) . . . . . . . . . . . . . 6-9 Parking Brake - Automatic . . . . . . . . . 6-10 Appendix 6-1 - Brake Caliper Noise . . . . . 6-13 Appendix 6-2 - Vacuum Brake Bleeder . . . . . . . . . 6-15 Appendix 6-3 - Brake Lining Life Expectancy . . . . . . . . 6-14 SECTION 7 - ENGINE . . . . . . . . . . . . . . . . . . 7-1 Principles of Increased Engine Life . . . . . . . 7-1 Gasoline Engine . . . . . . . . . . . . . . . . . . . . . . 7-2 Diesel Engine . . . . . . . . . . . . . . . . . . 7-2, 7-2A-B Exhaust Manifolds . . . . . . . . . . . . . . . . . . . . 7-3 Table - 2 Service Tips . . . . . . . . . . . . . . . . . . . . . . . . . 7-3 Nodular Iron Manifold Shrinkage . . . . . . . 7-3 Cast Iron Manifold Cracking . . . . . . . . . . 7-3 Cast Iron Warping . . . . . . . . . . . . . . . . . . . 7-3 Exhaust Manifold and Plug Wire Failure . 7-4 Exhaust Manifold Leaks . . . . . . . . . . . . . 7-4 Left Exhaust Pipe to Engine Oil Filter Interference . . . . . . . . . . . . . . . . 7-4 Engine Lubrication . . . . . . . . . . . . . . . . . . . . 7-6 General Description . . . . . . . . . . . . . . . . . 7-6 Oils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Quality . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Viscosity . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Temperature . . . . . . . . . . . . . . . . . . . . . 7-8 Energy Conserving Oils . . . . . . . . . . . . 7-8 Synthetic Engine Oils . . . . . . . . . . . . . . 7-8 Maintenance and Inspection . . . . . . . . . . 7-9 Checking Oil Level . . . . . . . . . . . . . . . . 7-9 Changing the Oil .. . . . . . . . . . . . . . . . . . 7-9 Changing the Oil Filter . . . . . . . . . . . . . 7-9 454 Engine Oil Fill Capacity . . . . . . . . . 7-9 Dipstick Replacement . . . . . . . . . . . . 7-10 Appendix 7-1 - Guideline For Engine Oil Consumption . . . . . . . . . . 7-11 Engine Cooling System . . . . . . . . . . . . . . . 7-13 General Description . . . . . . . . . . . . . . . . 7-13 Thermostat . . . . . . . . . . . . . . . . . . . . . . . 7-13 Engine Cooling Fans . . . . . . . . . . . . . . . 7-14 Radiator/Heater and Engine Deaeration System . . . . . . . . . . 7-16 Maintenance and Inspection . . . . . . . . . 7-17 Coolant Level . . . . . . . . . . . . . . . . . . . . . 7-17 Thermostat Check . . . . . . . . . . . . . . . . . 7-18 Flushing Cooling System . . . . . . . . . . . . 7-19 Appendix 7-2 - Radiator Additives . . . . . . 7-20 Appendix .7-3 - Engine Cooling Instructions To RV Manufacturers . . . . . . 7-21 Engine Fuels . . . . . . . . . . . . . . . . . . . . . . . . 7-22 Gasoline Engine . . . . . . . . . . . . . . . . . . . 7-22 Fuel Types . . . . . . . . . . . . . . . . . . . . . . 7-22 Diesel Engine . . . . . . . . . . . . . . . . . . . . . 7-23 Fuel Types . . . . . . . . . . . . . . . . . . . . . . 7-23 Appendix 7-4 - Use of Gasohol In Gasoline Engines . . . . . . 7-24 Appendix 7-5 - Methanol/Gasoline Blends Pose Potential Problems . . . . . 7-25 Engine Fuel Systems . . . . . . . . . . . . . . . . . 7-29 Gasoline Engine . . . . . . . . . . . . . . . . . . . 7-29 System Description . . . . . . . . . . . . . . 7-29 Fuel Tank . . . . . . . . . . . . . . . . . . . . 7-29 Fuel Pump . . . . . . . . . . . . . . . . . . . . 7-29 Evaporative Control System . . . . . . 7-29 Fuel Filters . . . . . . . . . . . . . . . . . . . 7-30 Carburetor . . . . . . . . . . . . . . . . . . . . 7-31 TABLE OF CONTENTS (Cont'd) Maintenance and Inspection . . . . . . . 7-31 TBI Fuel Injector - General . . . . . . . . 7-31 Closed and Open Loop . . . . . . . . . . . . 7-32 Fuel Control Operation . . . . . . . . . . . . 7-32 TBI Injector . . . . . . . . . . . . . . . . . . . . . 7-33 TBI Pressure Regulator . . . . . . . . . . . 7-33 Idle Control . . . . . . . . . . . . . . . . . . . . . 7-34 Throttle Position Sensor (TPS) . . . . . . 7-34 Fuel Pump Circuit . . . . . . . . . . . . . . . . 7-35 Fuel Line Filter . . . . . . . . . . . . . . . . . . 7-35 Fuel Tank . . . . . . . . . . . . . . . . . . . . . . 7-36 Evaporative Emission Control . . . . . . 7-36 Diesel Engine . . . . . . . . . . . . . . . . . . . . . 7-36 System Description . . . . . . . . . . . . . . 7-36 Maintenance and Inspection . . . . . . . 7-37 Water in Fuel . . . . . . . . . . . . . . . . . . 7-37 Primary Fuel Filter Water Drain . . . 7-37 Secondary Fuel Filter . . . . . . . . . . . 7-38 Appendix 7-6 - Plugged Fuel Return Line and Engine Performance . . . . . . . . . . 7-39 Appendix 7-7 - Vapor Lock Cause and Cure . . . . . . . . . . . . . . 7-40 Appendix 7-8 - Troubleshooting Aftermarket Fuel Systems . . . . . . . . . . 7-50 Appendix 7-9 - Secondary Fuel Systems . . . . . . . . . . 7-52 Engine Electrical System . . . . . . . . . . . . . . 7-55 Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-55 General Description . . . . . . . . . . . . . . 7-55 Ratings . . . . . . . . . . . . . . . . . . . . . . . . 7-55 Maintenance and Inspection . . . . . . . 7-55 Visual Inspection . . . . . . . . . . . . . . 7-56 Built-In Hydrometer (Delco Sealed-Top Battery) . . . . . . . 7-56 Electrical Load Test (Delco Sealed-Top Battery) . . . . . . . 7-57 Jump Starting - With Auxiliary (Booster) Battery . . . . . . . 7-57 Multi-Battery Electronic Jump Starting Aid . . . . . . . . . . . . . . 7-58 Battery Removal and Replacement . . . . . . . . . . . . . . 7-59 Starting (Cranking) System . . . . . . . . . . 7-59 General Description . . . . . . . . . . . . . . 7-60 Maintenance and Inspection . . . . . . . 7-61 Starting Problems (High Ambient Temperatures) . . . . 7-61 Starting Problems (Poor Ground) . . . . . . . . . . . . . . . . . 7-61 Charging System . . . . . . . . . . . . . . . . . . 7-62 'General Description . . . . . . . . . . . . . . 7-62 Generator Sizing and Selection . . . . . 7-62 Battery Isolator . . . . . . . . . . . . . . . . . . 7-62 Typical RV Isolator Voltmeter Checks . . . . . . . . . . . . . . 7-63 Typical RV Isolator Failure Modes . . . . . . . . . . . . . . . . . 7-63 Charging System - 1987 to Current . . . . . . . . . . . . . . . . . . . . . . 7-64 . CS Series Generator and Isolator Diagnosis . . . . . . . . . . . . . . . 7-65 Solid State Isolator . . . . . . . . . . . . . . . 7-65 Electromechanical Isolator . . . . . . . . 7-65 Maintenance and Inspection . . . . . . . 7-65 Ignition System . . . . . . . . . . . . . . . . . . . . 7-66 General Description . . . . . . . . . . . . . . 7-66 H.E.I . Distributor . . . . . . . . . . . . . . . . . 7-66 Secondary Wiring . . . . . . . . . . . . . . 7-67 Spark Plugs . . . . . . . . . . . . . . . . . . . 7-67 Ignition Timing . . . . . . . . . . . . . . . . 7-69 Maintenance and Inspection . . . . . . . 7-69 H .E.I. Distributor . . . . . . . . . . . . . . . 7-69 H .E.I. Test Procedure . . . . . . . . . . . 7-69 General Test . . . . . . . . . . . . . . . . 7-69 Module Test . . . . . . . . . . . . . . . . 7-70 Checking H .E.I . System Connections . . . . . . . . . . . . . . . . . . 7-70 Spark Plug Wires . . . . . . . . . . . . . . 7-70 Spark Plugs/Plug Puller . . . . . . . . . 7-71 6.2L Diesel Glow Plug Electrical System . . . . . . . . . . . . . . . . . . 7-71 General Description . . . . . . . . . . . . . . 7-71 System Components . . . . . . . . . . . 7-71 . Maintenance and Inspection . . . . . . . 7-74 Glow Plug Test . . . . . . . . . . . . . . . . 7-74 Appendix 7-10 - Battery Size and Cranking vs. Temperature . . . . . . . . . 7-75 Appendix 7-11 - Add-On (Auxiliary) Electrical Equipment Installations . . . . . . . . . . 7-79 Appendix 7-12 - "Hot Start" Problem Conditions . . . . . . . . . . . 7-80 Appendix 7-13 - Starter Motor Engagement After Initial Start-Up . . . . . . . . 7-83 Appendix 7-14 - Generator Belt Usage on 6 .2L Diesel Engines . . . . 7-84 Appendix 7-15 - Torsional Isolator . . . . . . 7-85 Appendix 7-16 - Electronic Cruise Control . . . . . . . . 7-86 Engine Emission Controls . . . . . . . . . . . . . 7-92 Vehicle Emission Control Information Label . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-92 Emission Controls - Systems and Components . . . . . . . . . . . . . . . . . . . . . . 7-92 General Description . . . . . . . . . . . . . . 7-92 Positive Crankcase Ventilation (PCV) System - Gasoline Engine . . . . . . 7-92 Crankcase Ventilation - Diesel Engine . . . . . . . . . . . . . . . . . . . . . . . 7-93 Table - 3 TABLE OF CONTENTS (Cont'd) Early Fuel Evaporation (EFE) System - Gasoline Engine . . . . . . 7-93 Thermostatic Air Cleaner (Thermac) - Gasoline Engine . . . . . . . . . . . . . 7-93 Evaporative Emission Control System (EECS) . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-94 General Description . . . . . . . . . . . . . . 7-94 Fuel Vapor Canister - Primary . . . 7-95 Fuel Vapor Canister - Auxiliary . . 7-96 Maintenance and Inspection . . . . . . . . . 7-97 Positive Crankcase Ventilation (PCV) - Gasoline Engine . . . . . . . . . . . . . . . . . 7-97 Checking the PCV System . . . . . . . . . 7-97 Early Fuel Evaporation (EFE) . . . . . . . . . 7-97 Inspection . . . . . . . . . . . . . . . . . . . . . . 7-97 Checking EFE System . . . . . . . . . . . . 7-97 Air Injection Reactor (A .I .R.) System - Gasoline Engine . . . . . . . . . . . . . . . . . 7-97 Inspection . . . . . . . . . . . . . . . . . . . . . . 7-98 Air Pump Drive Belt Adjustment and Replacement . . . . . . . . . . . . . . . . 7-99 Check Valve Inspection . . . . . . . . . . . . . 7-99 Thermostatic Air Cleaner . . . . . . . . . . . . 7-99 Checking Thermac Air Cleaner . . . . . 7-99 Thermometer Check of Sensor . . . . . 7-99 Air Cleaner Element and PCV Filter Replacement . . . . . . . . . . . . 7-99 .. . . . . . . Appendix 7-17 - H5D Emission System . . . . . . . . . . . . . 7-101 SECTION 8 - TRANSMISSION . . . . . . . . . . General Description . . . . . . . . . . . . . . . . . Models 350C and 400-475 Series . . . . . Torque Converter Clutch . . . . . . . . . . . Controls . . . . . . . . . . . . . . . . . . . . . . . . 8-1 8-1 8-1 8-2 8-2 Manual Linkage . . . . . . . . . . . . . . . . . . 8-2 Vacuum Modulator System . . . . . . . . . 8-2 Downshift (Detent) Cable System - 350C Transmission - G-Series . . . 8-2 Detent Downshift Electrical Circuit - 400-475 Series Transmission . . . . . . . . 8-2 Maintenance and Inspection . . . . . . . . . . . . 8-3 Fluid Level and Appearance . . . . . . . . . . 8-3 Capacity . . . . . . . . . . . . . . . . . . . . . . . . 8-3 Checking and Adding Fluid . . . . . . . . . 8-4 Changing Fluid . . . . . . . . . . . . . . . . . . . 8-4 Automatic Transmission Manual Linkage . . . . . . . . . . . . . . . . . . . . 8-5 Cooler Lines . . . . . . . . . . . . . . . . . . . . . . . 8-5 Transmission Mount . . . . . . . . . . . . . . . . 8-5 Transmission Shifting . . . . . . . . . . . . . . . 8-5 Engine/Transmission Torque Converter/Clutch Balancing . . . . . . . . . . . 8-6 Overdrive Transmission 4L80E . . . . 8-6 Appendix 8-1 - Transmission Fluids and Cooler Tips . . . . . . . . . . . . . 8-7 Appendix 8-2 - Temperature Monitors . . . 8-10 Appendix 8-3 = Geared Road Speed Determination . . . . . . . . . 8-11 Appendix 8-4 - Checking Gear Ratios . - Single Drive Axles . . . . 8-12 APPENDIXES . . . . . . . . . . . . . . . . . . . . . . . . A-1 Appendix A - Drive Belts and Tension Specifications . . . . . . . . . . . A-1 Appendix B - Preparing the Motor Home for Storage . . . . . . . . . . . . . . A-5 Appendix C - Nut and Bolt Identification . . . . . . . . . . . . A-7 Appendix D - Weight Distribution and Helpful Conversions . . . . . A-15 INDEX WARRANTY SERVICE BULLETINS SECTION 1 -INTRODUCTION GENERAL INFORMATION Chevrolet chassis are available in two series for motor home use. These are the G-Series and the P-Series . G-SERIES MOTOR HOME CHASSIS The G-Series, or cutaway van, as it is commonly referred to before the addition of the motor home body, is a chassis which includes a full floor, frame, front cab (less back) and engine as shown in Figure 1-1 . Many . of the components including the front-end sheet metal, instrumentation, driving controls and seats are common with the Chevrolet Van . Figure 1-1 -G-Series Motor Home Chassis P-SERIES MOTOR HOME CHASSIS The P-Series motor home chassis is an engine and frame unit which includes the driving controls, as shown in Figure 1-2 . The P-Series (P30 is the series and size class used for motor homes) is available in five wheelbase lengths . These are : Model Number CP CP CP CP CP 3112 31432 31832 31932 32032 - 52 52 52 52 Wheelbase Length (inches) 137 158 .5 178 190*" 208* *Start-up production 1988 model- year **Start-up production 1991 model year Figure 1-2- P-Series Motor Home Chassis IDENTIFICATION NUMBERS There are several numbers that are important in identifying the vehicle and components used on the vehicle . They are the Vehicle Identification Number (VIN) and the Service Parts Identification Label - Figure 1-4 SECTION 1 - INTRODUCTION P30 HD CUTAWAY MOTOR NOME P30 HD CUTAWAY AS A MOTOR HOME Comfortable, roomy cab with standard adjustable highback front bucket driver's seat. " Outstanding strength and durability if Class A chassis : best-in-class GVWRs from 10,500 lbs . up to 14,500 lbs . Ample use of glass for commanding view of the road. Ease of upfitting on full frame with industry standard straight frame rails . 4-speed automatic transmission (41-80-E) with overdrive electronically controlled for smooth shifting, powerful torque multiplication and economical highway operation . Choice of four wheeelbases : 158 .5-, 178-, 190-, and 208- inches . 4-wheel disc brakes for smooth, powerful braking (std. on 14,500 lbs. GVWR models). Can accommodate bodies of 22-, 24-, 26- and up to 27- feet in length . Solor-RayTm light tinted glass reduces interior vehicle temperature in cab area for greater driver/passenger comfort . 7.4 liter (454 cubic inch) fuel-injected V8 gasoline engine with 230 horse-power and 380 lbs.-ft. of torque . Improvements to the 7.4-liter (454) V8 gasoline engine include revised inlet manifold, new hydrodynamic front crank seal and much more. Smooth-riding independent front suspension to step over bumps plus tapered leaf springs to enhance vehicle stability . Dual rear wheels provide outstanding stability and enhanced ride smoothness . " Up to 5,000-Ib ..capacity on front axle; up to 10,000-Ib . capacity on full-floating rear axle. STANDARD INTERIOR CONTENT Air conditioning : front One-piece fiberglass hood with grab handles that tilts forward for easy access to engine and other under-thehood components. Armrest: left hand padded Fiberglass cab-entry steps for lifetime protection against corrosion . Dome lamps : with front-door activated switches B-pillar grab handles for easy access to cab . Cigarette lighter : included on instrument panel Floor coverings : embossed black rubber mat on front floor area and wheelhousings 1-1A Gages: speedometer, odometer, trip odometer, fuel level, voltmeter, oil pressure, engine temperature and additional tell-tale lights Headliner: hardboard Heater: deluxe outside air heater and defogger Insulation : in cab area Parcel Tray: on top surface of instrument panel extension: includes beverage holder provisions Radio : electronically-tuned AM radio with digital clock and fixed mast antenna Seats: adjustable high-back front bucket driver's seat with all-vinyl trim Steering Wheel : 2-spoke, with anti-theft feature on steering column Stowage Box: with latched door on front face of instrument panel extension Sunshades : padded, color-keyed RH and LH sunshades Windshield Wipers: intermittent wiper system STANDARD EXTERIOR CONTENT Bumpers: chrome front Headlamps : quad rectangular halogen Horn : electric dual high-note and low-note Tires: six LT215/85FI16C steel belted radials (158.5 inch wheelbase) six 7.50/16LT/D nylon ply blackwalls (178 inch wheelbase) six 8.0013/19.5/D steel belted radial blackwalls (190 and 208 inch wheelbases) Undercoating : on step panels and front wheelhousings Wheels : six painted steel Windows : light tinted Solor-RaVrl glass on all windows SECTION 1 - INTRODUCTION VEHICLE IDENTIFICATION NUMBER (VIN) The VIN is the legal identification of the vehicle. It appears on a plate which is attached to the top left of the instrument panel on the G-Series chassis and can be easily seen through the windshield from outside the vehicle (Figure 1-3). On the P-Series chassis the VIN is attached to the front of the dash and toe panel to the left of the steering column. (See Figure 1-2) for pre 1990 . .Currently the VIN plate is located center and on top of the radiator support. The VIN also appears on the Vehicle Certificates of Title and Registration . Refer to Figure 1-4 to determine the vehicle manufacturer, model and chassis type, engine type, GVW range, model year, plant code and production sequence number. Figure 1-3- Vehicle Identification Number (VIN) G 3 1 2 GVWR/BRAKE SYSTEM Code GVWR Range Brake System B 3001-4000 Hydraulic C 4001-5000 Hydraulic D 5001-6000 Hydraulic E 6001-7000 Hydraulic F 7001-8000 Hydraulic G' 8001-9000 Hydraulic H 9001-10,000 Hydraulic J 10,001-14,000 Hydraulic K 14,001-16,000 Hydraulic ' Includes G-Van Bus 9 1 9 Production Sequence Number Nation of Origin 1 = U .S . Built 2 = Canadian Built 3 = Mexican Built Code Make A Chevrolet Bus' B Chevrolet Incomplete C Chevrolet Truck D GMC Incomplete E Cadillac Incomplete H GM of Canada Bus T GMC Truck IGJ GMC Van/Bus IGK GMC MPV IGN Chevrolet MPV 'Van with 4th Seal 4 Code Body Type 0 Pickup/Panel Delivery 1 Hi-Cube/Cutaway Van 2 Forward Control 3 Four-Door Cab 4 Two-Door Cab 5 Van 6 Suburban 7 Motor Home Chassis 8 Utility (Jimmy/Blazer) 9 Stake Code R D V G P S T M Line and Chassis Type Chassis Line Type Conventional Cab 4 x 2 Military Truck 4 x 4 Conventional Cab 4 x 4 Van 4 x 2 Forward Control 4 x 2 Sm Conventional Cab 4 x 2 Sm Conventional Cab 4 x 4 Sm Van 4 x 2 Figure 1-4- Vehicle Identification Number Codes Code A B C D E F G FI J K L M N Year - 1980 -1981 -1982 -1983 -1984 -1985 -1986 -1987 -1988 -1989 -1990 -1991 -1992 I Code C E F H J K M N R W Z B F J S E V Z 1 2 3 4 7 8 0 Assembly Plant Baltimore, MD Flint, MI Janesville, WI St . Louis, MO Pontiac East, MI Pontiac, MI Fort Wayne, IN Oshawa, ON Moraine, OH Detroit, MI Scarborough, ON Lordstown, OH Shreveport, LA Pontiac, MI Engine Type and Make Producer Type DDAD 6 .2L V8 Diesel Pontiac 2 .5L L4 TBI Powertrain 6 .5L V8 Diesel Chevrolet 5 .OL V8 TBI DDAD 6 .2L V8 Diesel Chevrolet 5 .7L V8 TBI Chevrolet 5 .71 V8 4BBL Chevrolet 7 .4L V8 TBI Chevrolet 2 .BL V6 TBI Chevrolet 7 .4L VB 4BBL Chevrolet 4 .3L V6 TBI RPO LH6 LN8 L65 L03 LL4 LOS LT9 L19 LL2 LE8 LB4 SECTION 1 INTRODUCTION SERVICE PARTS IDENTIFICATION LABEL Service Parts Identification^~~~ '' 1G?KP37WXK3300831 C7S DET D1Yr ENV E5Z M40 NA9 N32 NN4 RoE YSN ZW9 Z5P 01L OIU The Service Parts Identification Label (Figure 1-5) is provided on both G- and P-Series vehicles. On the G-Series vehicle, the label is located on an inner hood panel surface. On the P-Series vehicle, the label is located on an inner body panel by the body builder . The label lists the vehicle identification number, wheelbase, and all production options or special equipment on the chassis when it was shipped from the factory including paint information . ALWAYS REFER TO THIS INFORMATION WHEN ORDERING PARTS . EOC SLM 5Y9 E?Z VJ9 DO NOT REMOVE 178 .0 G61 HF7 V73 XSN JF9 Y36 K68 Y97 CP31532 LE°_ MX1 Y38 YP5 xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxlcxx ORDER NO 582JJJ Figure 1-5-Service Parts Identification Label MOTOR HOME TOWING The term. "GCWR" is a new term to be learned when the motor home operator decides to enter the "world of towing ." The term GCWR refers to the Gross Combination Weight Rating which includes the combined weight of the motor home (or truck) with all of its contents and the total weight of the trailer, car, boat or whatever is being towed . Mini- and full-size motor homes do not have specific charts that cover trailer towing requirements . The chart shown in Figure 1-6 has been taken from the Chevrolet Trailer Guide and is presented as an aid to the motor home owner to assure reasonable performance without placing undue stress on the driveline components. The chart covers all engine and axle combinations used within General Motors, however all combinations are not available in the motor home product . Additional information may be available from the various motor home manufacturers as well as the current Chevrolet Trailer Guide . Examine the rating for your motor home provided by the RV manufacturer. Refer to pages 5-3, 6-14, 7-1 and 8-7 for additional charts and information relating to work/stress and vehicle component life expectancy. CAUTION : TO HELP AVOID PERSONAL INJURY DUE TO POOR BRAKING ACTION, ADEQUATE SIZE TRAILER BRAKES ARE REQUIRED ON TRAILERS OVER 1000 POUNDS OF LOADED WEIGHT. GROSS COMBINATION WEIGHT RATING (GCWR) Includes Weight of Both Truck and Trailer By Engine & Axle Ratio For Recreational Applications GCWR (lb .) ENGINES 6000 M00 2 .5L 1151) 4 GAS 2 .6L 073) V6 GAS 43L 1252) V6 GAS SJII (305) V6 GAS 3.73 4.10/4.11 5 .71. J350) V6 GAS 62L V6 DIESEL 7 .41. 14M) VB GAS 2 .41 7000 7500 3 .42 2 .56 2 .41 3 .73/4.11 2 .73 2 .56 6000 6500 9000 3 .731 3 .08 2 .73 2 .73 9500 10,000 10,500 1t= REAR AXLE RATIOS 3.42 3.08 2 .73 3 .08 3.23 3 .73 3 .08 3 .42 4 .11 3 .42 3 .23 3 .42 3 .73 11,500 3.73 12,000 12,500 13,500 14,000 3.21 4 .10 4 .56 3 .42 5.13` _3.7_3 4.10 14,500 15,000 16,000 19,000 4 .10 4.5N4.88' 4 .56 3 .73 'Motor Home Chassis only 'Available only when RPO KC4 Engine Oil Cooler is specified. THIS CHART SHOWS THE MAXIMUM ALLOWABLE GROSS COMBINATION WEIGHT RATING (GCWR) BASED ON ALL OF THE AVAILABLE TRUCK ENGINES AND REAR AXLE RATIOS WITH AUTOMATIC TRANSMISSIONS . THE GCWR INCLUDES THE TOTAL LOADED WEIGHT OF BOTH THE TRUCK AND TRAILER . ANY AVAILABLE ENGINE MAY BE USED FOR TRAILERING IF THE GCWR SHOWN IS NOT EXCEEDED . NOTE : THE TRAILER WEIGHT CAN BE INCREASED BY 25% IF THE VEHICLE SPEED WILL NOT EXCEED 25 MPH . Figure 1-6 - Gross Combination Weight Rating Chart NOTE: GCWR for unit with 4L80E transmission is 20,000# with 4:63 or 5:13 ratio. SECTION 1 INTRODUCTION ABOUT RV WEIGHTS A discussion of recreational vehicle weight ratings, how they are determined, and how exceeding these figures can affect the operation of the vehicle. By C. JAY HAYNOR, F15585 One of the organizations involved in establishing definitions that motorhome manufacturers and chassis builders use is the Recreation Vehicle Industry Association (RVIA) . The weight issue is equally important to consumers . So, Recently, Paul, a friend of mine who owns a large auto let's consider some ofthe definitions that we coach owners parts warehouse, was talking with me about one of his delivery trucks. The truck was a 1986 model with a gross should understand before taking the next step, which is vehicle weight rating (GVWR) of 11,000 pounds . This same actually weighing our motorhomes. chassis is used by motorhome manufacturers to build Class C coaches . The truck gave excellent service for eight Two definitions exist for the term chassis as it applies to months. Not too long after that, however, all of the drive- motorhomes. In the case of a Class A motorhome, the shaft universal joints wore out, and multiple disc brake pad chassis consists of the frame, running gear, steering, and and rear brake shoe replacements were necessary. These suspension system . In the case of a Class C or micro-miniand other repairs were causing Paul some concern . He motorhome, the chassis includes the same components as noted that the fronttires were cupped severely, and the rear does a Class A motorhome chassis plus a cab. tires had sidewall cracks . Paul's question to me . was, ? From the definitions above, we can clearly see that the "Why?" chassis is, separate from the body or coach in a Class A When I talked with a few of the employees, they confirmed motorhome and separate from the motorhome body in a my suspicions . It seems that one of the salesmen was Class C coach . It is the chassis manufacturer that deterselling to a new account and used this truck to deliver some mines the weight ratings and load specifications . The only of the "parts ." The "parts" included pallets of oil, transmis- exception would be if the chassis were modified and recersion fluid, and batteries . The truck was overloaded and, tified by the company performing the modification . This equally important, subjected to poor weight distribution. would be indicated on a label positioned near the original The load on the rear was excessive, thereby cracking the label on the coach . The location of these labels varies from sidewalls on the rear tires. The excessive rear load also vehicle to vehicle . lowered the rear of the truck, thereby raising the front. Because of that, the front tires made less contact with the Gross vehicle weight rating (GVWR) is the weight speciroad, and cupping resulted . This reminded me of pictures fied by the chassis manufacturer as the maximum loaded I once saw of a Federal Express airplane that was so weight of the vehicle (including driver and passengers) . heavily loaded in the rear that the front of the plane actually Sometimes a tag axle -a non-powered rear axle- is added lifted well off the ground . The truck instance, though not as to a chassis . This usually is done to increase the GVWR of dramatic, was an example of the same type of overload the chassis, and, as previously mentioned, it becomes the condition . And many of the other mechanical difficulties responsibility of that party to post and certify the new that the truck began to experience could be attributed to GVWR. overloading . Gross axle weight rating (GAWK) is specified by the The major components of a chassis- including the engine, chassis manufacturer as the load carrying capacity of a transmission, brakes, axles, tires, and frame - are single-axle system as measured at the tire-ground interdesigned to accommodate a particular weight, and if these face (in other words, at the place where the tire meets the components are overloaded, their life expectancy dimi- ground) . It is important to note that the GAWK is limited to the lowest individual rating of the tires, the wheels, the nishes rapidly. springs, or the axle - in other words, whichever component In the "good ole days" weight ratings were more guidelines is the weakest link in the chain. Therefore, changing from than rigid "to the ounce" specifications . Then, along came load range D to load range E or F tires may or may not the energy crunches of the 1970s . As a result, fuel econ- increase the GAWK, since this rating could be dependent omy and production costs became critical . Automobile upon other (weaker) components . The GAWK assumes manufacturers and RV manufacturers found that one of the that the weight is evenly distributed over the axle, with 50 fastest and easiest ways to increase fuel economy and percent on the right side and 50 percent on the left side to reduce production costs was to lighten the vehicles not 70/30, for instance. In other words, in the case of an wherever they safely could . Today, more than ever before, axle with a GAWK of 6,000 pounds, the load distribution . it is of the utmost importance that we pay more attention to should be 3,000 pounds on one side and 3,000 pounds on technical definitions and weights as they relate to our the other. homes on wheels . Technical Editor SECTION 1 INTRODUCTION Axle weight is both the amount of weight carried by a be due to improperly positioning heavy materials so that single axle and the amount of weight transmitted to the the load is centered over one rear tire or so far forward on highway by one axle. the body that the front axle and tires are overloaded . An understanding of the proper methods of load placement Shipping weight is the average weight of a specific will enable coach owners to prevent an overload condition . vehicle as it leaves the assembly plant, including grease It should be noted also that the limiting factor is the weight and oil plus regular production options but without any pri- rating, not the cubic foot capacity of the storage compartmary mover engine fuel (gasoline or diesel fuel) . ments . Some motorhome owners may be under the impression that if the manufacturer has provided the Empty weight is defined as the shipping weight of a spe- space, it must be acceptable for them to fill each nook and cific vehicle plus the maximum weight of primary mover cranny to capacity . This isn't always the case, however . By engine fuel (gasoline or diesel fuel). providing varied and ample storage space, motor coach manufacturers are attempting to meet a multitude of Curb weight is the weight of the vehicle empty (without needs . payload and driver) but including engine fuel, coolant, engine oil, tools, spare tire, and all other standard equip- Weighing your coach . Of course, the only way to be sure ment. It is determined without water in the tanks or water to avoid an overload condition is to weigh the coach. To do heater and with empty LP-gas containers . (Note: This so accurately, the coach owner needs to find a scale that definition, while accepted within the RV industry, may has a level area on the side, and to develop an excellent differ from definitions utilized by governmental regulatory rapport with the person doing the weighing . The level side agencies.) area is very important, because it will be necessary to have 50 percent of the left and right sides of the coach off the Wet weight is the empty weight of a specific vehicle with scale during some of the weighing . If the side area is not the fresh water tanks, water heater, and LP-gas containers level, the side weights will be incorrect . Suitable scales full but with waste water holding tanks empty. This weight might be found at truck stops, sand and gravel pit operais particularly significant to motorhome owners, because tions, and moving companies . when you subtract this figure from the gross vehicle weight rating, you have a fairly accurate indication of the amount I would suggest that you make a photocopy of the coach of weight that can be added to the vehicle, including driver weighing worksheet that accompanies this article and use and passengers, clothing, foodstuffs, etc . it as a reference at the scale. Weigh the coach at an off time, since the entire process can take up to one-half hour. Payload is a term commonly used in the trucking industry. Before weighing the coach, load it as you normally would In the RV industry, the term carrying capacity also is used. for travel, including food, clothing, fuel, water, propane, etc . Carrying capacity is defined as the average weight that can This is not the time to be conservative! be added to a specific vehicle without exceeding the GVWR. Carrying capacity can be computed by subtracting The worksheet divides the coach into four sections. This is the empty weightof the vehicle from the GVWR figure . The done by finding the halfway point between the front and addition of any other equipment or cargo and passengers rear tires (axles) and the halfway point between the front adds to the vehicle weight and subtracts from the allowable tires and then the halfway point between the rear tires. Do carrying capacity. It is important to remember that the limit- not simply use the distance between the front and rear of ing factor in this rating could be the axles, springs, tires, the coach body; be sure to use the axles as a reference transmission parking pawl, or any other equipment . point. Use tape to mark the side-to-side halfway points on the front bumper and on the rear bumper to make the referCenter of gravity is the point where the weight of the ence points easily visible . Do the same for the front-to-rear chassis and/or body and payload is concentrated and, if halfway points by applying tape to the side of the coach. suspended at that point, would balance front-to-rear and Dirve the coach onto the scale to the point that the front-toside-to-side . Cornering, acceleration, and other forces are rear tape pieces indicate that one-half of the wheelbase is considered as acting on a vehicle's center of gravity. Thus, on the scale and one-half is off . Referring to the worksheet, it has a great influence on body lean and other handling this will be weight number W1 . characteristics . Even if all of the weights fall within the specifications, if they are not distributed properly, the coach could still suffer from excessive body lean or substandard handling characteristics. It should be noted that the center Weigh the tow car as you normally tow of gravity of a basement model coach will be higher than that of a traditionally designed motorhome . it, and if you find that it is overloaded, Weight distribution is the arrangement of body and payload weight on a vehicle's chassis . It has a very definite bearing on the life of the tires, axles, springs, frame, and other parts. The factthat the total weight of the vehicle does not exceed the recommended maximum GVWR does not insure that the coach is not overloaded. Overloading can remove any weight necessary to bring it into specifications. Next drive the entire motorhome onto the scale . This will be weight number W2. Then drive off the scale so thatthe side SECTION 1 INTRODUCTION tape stripe indicates that the rear half of the chassis remains on . This will be weight W3. I emphasize that it is important that one-half of the chassis, not the coach, rests on the scale during weighing . Weight number W1 should, not exceed the GAWK for the front axle. Weight number W2 should not exceed the total GVWR. Weight number W3 should not exceed the rear axle GAWR . important . Use the front and rear axle weights on the worksheet to determine the proper air pressure by consulting the tire manufacturer's tire manual, which should be available at any tire store . One last word of caution : start with the weight you would normally carry when traveling . If the weight places the vehicle over the GVWR, remove some weight and weigh the coach again. The importance of weight and weight distribution in terms of safety and your motorhome's overall Now comes the time when rapport with the scale attendant health cannot be overemphasized . and patience come in handy. To make these weights more meaningful, use the side-to-side and front-to-rear tape Another term with which motorhome owners should be is gross combination weight rating (GCWR), pieces to divide the chassis up into quarters and then weigh familiar which is the value specified by the chassis manufacturer as each section : front left, weight zone W4; rear left, weight zone W6; front right, weight zone W5; and finally rear right, the maximum allowable total loaded weight of the tow and trailer combination . For our purposes the tow weight zone W7. The weights for zone W4 and zone W5 vehicle vehicle is the motorhome, and the trailer ordinarily is a should be about equal, as should the weights for zones W6 and W7. If this is not the case, try to move items inside the towed car. To determine what size car can be towed safely behind a motorhome, subtract the actual motorhome coach to bring the weights close . weight, which must be less than the GVWR, from the GCWR. Normally this weight will be approximately 3,000 When you compare the total weight of the two front quar- pounds, in which case the towed car combination (includters to the total axle weight, the figures probably will not be ing trailer, dolly, or tow bar) should not exceed 3,000 exactly equal, but they should be close. The same applies pounds . Weigh the tow car as you normally tow it, and if you to the rear axle . It is also possible that the front and rear find that it is overloaded, remove any weight necessary to GAWR when totaled will be more than the GVWR. This is bring it into specifications . because the limiting factor may be something such as the transmission parking pawl, braking capacity, or another I hope this short discussion of motorhome weights will component . motivate you to weigh your coach and make any necessary adjustments . And if you're looking for a new coach, it is Since tire manufacturers determine pressure recommen- hoped that this article will be another factor in your dations for each individual tire based on the weight that a selection . particular tire is carrying, these quartered weights are very SECTION 1 - INTRODUCTION LUBRICATION Various components of the motor home chassis must have the proper lubrication to operate as designed. This lubrication must be done in accordance with the intervals specified in the appropriate Maintenance Schedule for the vehicle . Following are charts which list the recommended fluids and lubricants, component fluid capacities and lubrication points . RECOMMENDED FLUIDS AND LUBRICANTS FLUID/LUBRICANT USAGE Power steering system and pump reservoir Power steering fluid, GM Part No. 1050017 or equivalent Manual steering gear Lubricant, GM Part No. 1052182 or equivalent Differential - Standard or Locking Spiral Bevel Axel Gearing . Pinion enters ring gear at centerline SAE-80W GL-5 or SAE-80W-90 GL-5 gear lubricant (SAE-80W - GL-5 in Canada) Do not use additive with Eaton locking differential Differential - Rockwell model C-103-12 1/4", Commercial P model, Hypod gearing . Pinion enters ring gear below centerline. SAE-85W-140 GL-5 above 10 °F SAE-80W-90 GL-5 below 15°F Military spec 2105C Brake system and master cylinder Delco Supreme 11 fluid or DOT-3 1052535 Propeller shaft slip spline and U joints Chassis Grease, GM Part No. 1052497 or equivalent Hood Latch Assembly a. Pivots and spring anchor b. Release pawl a. Engine Oil b. Chassis Grease Hood and Door Hinges Engine Oil Automatic Transmission Shift Linkage Engine Oil Chassis Lubrication Chassis Grease, GM Part No. 1052497 or equivalent Engine Oil (Gasoline) "SG" or "SG/CC" or "SG/CD" Engine Oil Engine Oil (Diesel) "CE/SG" Engine Oil Automatic Transmission DEXRON IIE Auto. Trans. Fluid, GM Part No. 12345881 Parking Brake Cables Chassis Grease, GM Part No. 1052497 or equivalent Front Wheel Bearings Wheel bearing lubricant, GM Part No. 1051344 (One Pound) or Exxon Ronex MP Grease or equivalent Body door hinge pins, tailgate hinge and linkage, folding seat, fuel door. hinge Engine Oil Windshield Washer Solvent GM Optikleen washer solvent, GM Part No. 1051515 or equivalent Engine Coolant GM 1825M Specifications Mixture of water and high quality Ethylene Glycol base type antifreeze, GM Part No. 1052753 or equivalent Key Lock Cylinder Lockeze or GM Part No. 12345120 Figure 1-7 = Recommended Fluids and Lubricants SECTION 1 INTRODUCTION LUBRICANT CAPACITIES USAGE U .S. MEASURE Differential 10-1/2 In. Ring Gear (Chevrolet) 10-1/2 In. Ring Gear (Dana 70) 9-3/4 In . Ring Gear (Dana) 10.5 In. Ring Gear (Saginaw 70) 11 .3 In. Ring Gear (Dana 80) 6-1/2 7.2 6.0 7 .0 7.5 pts . pts . pts . pts. pts . Engine Crankcase Code F-H LM-P 5 .7L V8 - Drain & Refill - w/Filter Change 4 qts . 5 qts . Code W 7.4L V-8 - Drain & Refill - w/Filter Change 6 qts . 7 qts . Code C-F-J 6 .2L-6 .5 V-8 Diesel Including Filter 7 qts . Transmission 350C 475 4L80E - Automatic Total Refill Total Refill Total Refill 10 3 11 3.5 13.5 7.7 qts . qts . qts . qts . qts . qts. Figure 1-8 - Lubricant Capacities NOTE: With any side fill gear case, regardless of specification, fill the case until fluid runs back out the fill hole (Figure 1-9). DO NOT CONSIDER THE FILL ADEQUATE JUST BECAUSE YOU CAN REACH IT WITH YOUR FINGER . Figure 1-9-Side Fill Gear Case Capacity SECTION 1 INTRODUCTION LUBRICATION POINTS 1~Control Arm Bushings and Ball Joints @Trans. Control Shaft @Tie Rod Ends @Wheel Bearings ©Air Cleaner - Element O7 Transmission - Automatic ®Steering Gear Clutch Cross-Shaft ® Rear Axle ~9 Oil Filter OO Brake Master Cylinder 11 Parking Brake Linkage Figure 1-10 - Lubrication Points - G-Series OLower Control Arms Upper Control Arms 3~Upper and Lower Control Arm Ball Joints ®Intermediate steering Shaft (PA10) O5 Tie Rod Ends © Wheel Bearings 07 Steering Gear ®Air Cleaner - Element O9 Master Cylinder Transmission - Automatic 11 Carburetor Linkage - V-8 Brake Pedal Spring Universal Joints* ® Rear Axle *On some models, universal joints are sealed with no provision for lubrication. On models which have lubrication provisions, use high-temperature lubricant (GM Part No. 1051344 or equivalent) . Figure 1-11- Lubrication Points - P-Series SECTION 1 - INTRODUCTION NOTE : TYPICALLY THERE ARE EIGHT LUBRICATION FITTINGS ON THE I -BEAM AXLE . Figure 1-12- Lubrication Points-- P-Series with I -Beam Axle (Option No. FS3) NOTE: See #13 Figure 1-11 . Grease must exit from all 4 bearings when lubricating U joints . Also grease spline on 2 and 3 shaft units . Grease must exit from spline plug . ADEQUATE TEMPERATURE MODULATION FROM DASH HEATER SYSTEMS Over the past few months, I've received a number of letters on the subject of inadequate temperature modulation from dash heater systems. When one moves the temperature control lever to any position between the cold and warm extremes, one expects modulated air. In some instances, however, that's not what one receives . The air is either too hot or too cold, and no temperature modulation is taking place. With the winter months almost upon us, it would seem that a brief discussion and modification suggestion is in order. Two different systems are used for modulating air temperature in engine-operated dash heating systems. One is excellent and the other is not so good . The excellent one is the blend air door control system . This system incorporates an air control door at the end of the temperature control lever. The door is controlled via the dash lever, which is connected to the door by a cable. To regulate the outlet temperature of the air, this cable moves the door to determine what percentage of incoming air will go through the heater core, which remains fully hot . The other system controls the outlet air temperature by controlling the flow of hot water through the heater core . All air is directed through the heater core . The other end of the temperature control cable is attached to a manual control lever in a water valve located in the heater hose that leads to the heater core . Therein lies the problem - attempting to control the water temperature on the heater core . As one moves the temperature control lever on the dash, a cable moves a door inside the water valve, which modulates the water flow to the heater core . Unfortunately, the flow is decreased but not by very much, since the pressure is increased. As the pressure is increased, so is the flow, and this compensates for the door blockage . Another reason is that while the flow of water is controlled, the temperature is not. When the temperature becomes too hot, one moves the lever toward cool, and then it is necessary to move it slightly more, more, and more, until the lever is in the cool position . At this point, the coolant now is totally blocked, and the hot air becomes cold within a few moments. So, one returns the lever to the warm position . It is unlikely that you will have a temperature modulation concern if your coach's dash heater is equipped with a blend air door system . To determine which system the coach has, you will have to find out whather the other end of the temperature control lever is connected to the heater case or a valve in a heater hose . If the cable leads to a water valve, similar to the one in Figure 1, your coach has the latter type of system, and an effective and inexpensive solution exists - install a temperature control valve with an "H" in it, similar to the one in Figure 2. This revised valve is easy to install after one removes the original valve. The only addition is that it must also be installed in the heater return hose, which requires two more heater hose clamps . The "H" valve system allows the blocked coolant to flow very easily into the return line . The result is a greatly improved system . I have talked with the folks at Acme Radiator, and they have indicated that they will provide the "H" system heater control valve to FMCA members for $20 postage paid . To order the valve - part number 4100173 - write to Acme Radiator and Air Conditioning Inc ., 17103 State Road 4 East, Goshen, I N 46526. C. Jay Haynor, F15585 SECTION 2 -- HEATING AND AIR CONDITIONING HEATING SYSTEM GENERAL DESCRIPTION The heating system consists of a heater core housed in a case which, typically, includes an air inlet, blower motor assembly, air distribution ducts and doors to control the flow of air through the case. The configurations of G-Series and P-Series assemblies differ . TROUBLE TROUBLESHOOTING THE SYSTEM Problems of too little or no heat, poor air circulation, or inadequate defrosting action are sometimes encountered with a heating system . The diagnosis chart (Figure 2-1) lists typical trouble symptoms, the probable causes, and what can be done to correct the condition . CAUSE AND CORRECTION Temperature of heater air at outlets too low to heat up passenger, compartment . 1. Refer to Chevrolet 10-30 Series Shop Manual. Temperature of heater air at outlets adequate but the vehicle will not build up sufficient heat. Check for body leaks such as: 1 . Floor side kick pad ventilators partially open . 2. Leaking grommets in dash. 3. Leaking welded seams along rocker panel and windshield . 4. Leaks through access holes and screw holes . 5. Leaking rubber molding around door and windows . 6. Leaks between sealing edge of blower and air inlet assembly and dash, and between sealing edge of heater distributor assembly and dash . Inadequate defrosting action . 1 . Check that DEFROST lever completely opens defroster door in DEF position Adjust if necessary. 2. Assure that temperature and air doors open fully - Adjust . 3. Look for obstructions in defroster ducts - Remove any obstructions . 4. Check for air leak in duct between defroster outlet on heater assembly and defroster duct under instrument panel - Seal area as necessary. 5. Check position of bottom of nozzle to heater locating tab - Adjust . 6. Check position of defroster nozzle openings relative to instrument panel openings. Mounting tabs provide positive position if properly installed . Inadequate circulation of heated air through vehicle . 1 . Check heater air outlet -for correct installation - Reinstall. 2. Inspect floor carpet to ensure that carpet lies flat under front seat and does not obstruct air flow under seat, and also inspect around outlet ducts to ensure that carpet is well fastened to floor to prevent cupping of air flow - Correct as necessary. Erratic heater operation . 1. 2. 3. 4. Hard-operating or broken controls . 1 . Check for loose bowden cable tab screws or misadjusted bowden cables Correct as required . 2. Check for sticking heater system door(s) - Lubricate as required, using a silicone spray. Check coolant level - Fill to proper level. Check for kinked heater hoses - Relieve kinks or replace hoses . Check operation of all bowden cables and doors - Adjust as necessary. Sediment in heater lines and radiator causing engine thermostat to stick open Flush system and clean or replace thermostat as necessary . 5. Partially plugged heater core - Backflush core as necessary. Figure 2-1 - Heating System Diagnosis SECTION 2 - HEATING AND AIR CONDITIONING AIR CONDITIONING RECEIVER-DEHYDRATOR P SERIES GENERAL DESCRIPTION The receiver-dehydrator, mounted near the condenser, serves as a reservoir for storage of high-pressure liquid produced in the condenser . It incorporates a screen sack filled with the dehydrating agent. Two types of air conditioning systems are used in Chevrolet Motor Homes. For the G-Series, a blend-air system is used. This system combines both the heating and cooling functions in one unit. Cooling only is provided with the system used on the P-Series . The P-Series system is installed by the body manufacturer . Both systems operate on the same basic principles of refrigeration. That is, a liquid refrigerant absorbs heat as it vaporizes, and loses heat as it condenses from a vapor back to a liquid . By varying the pressures within an air conditioning system, the refrigerant can be vaporized to absorb heat from inside the vehicle, and then condensed to release the heat to the outside atmosphere . System components include compressor, condenser, expansion tube (G-Series) or a thermostatic expansion valve (P-Series), evaporator, and an accumulator or a receiverdehydrator . In operation, the compressor produces the pressure which moves refrigerant through the system . Liquid refrigerant passing through the restriction of the expansion tube or valve changes into a vapor as it enters the low-pressure environment of the evaporator . (See Figure 2-2 .) a As it changes to a vapor, it absorbs heat from the air being circulated around the evaporator. Suction created by the compressor draws the refrigerant vapor through the line from the evaporator. The vapor, which has been under low pressure, is pumped out of the compressor under high pressure . The high pressure in this part of the system is due to the expansion tube (or thermostatic expansion valve) which places a restriction in the line. As the highpressure refrigerant vapor flows into the condenser, it changes to a liquid as it loses heat to the air flowing around the condenser. The liquid refrigerant flows through the line from the condenser to the expansion tube (or thermostatic expansion valve) to repeat the cycle. System temperature is controlled by running the compressor intermittently, automatically turning it on and off as necessary to maintain proper temperatures . The compressor is started and stopped through the use of an electromagnetic clutch on the compressor pulley . The clutch is operated by a pressure-sensing switch (Pressure Cycling Switch - G-Series) or a temperature-sensing switch (Thermostatic Switch - P-Series) . In addition to the components described above, the air conditioning system is also equipped with either an accumulator (G-Series), or a receiver-dehydrator (P-Series). The receiver-dehydrator, used primarily as a liquid storage tank, also functions to trap minute quantities of moisture and foreign material which may have remained in the system after installation or service operations. A refrigerant sight glass is built into the receiver-dehydrator to be used as a quick check of the state and condition of charge of the entire system . ACCUMULATOR G SERIES The accumulator is located at the evaporator outlet . Its most important function is not to "accumulate" although this too is important. Its primary function is to separate any liquid retained in the vapor from the evaporator, retain the liquid and release the vapor to the compressor. A bag of desiccant (dehydrating agent) is also located in the accumulator as a moisture-collecting device . NOTE: If the refrigerant system has been opened - that is, exposed to the atmosphere - the desiccant may have' absorbed a considerable amount of moisture . In such instances, the system must be evacuated before recharging. This process removes moisture from the system . G-SERIES SYSTEM Air, either outside air or recirculated air, enters the system and is forced through the system by the blower . As the air passes through the evaporator core, it receives maxImum cooling if the air conditioning controls are calling for cooling . After leaving the evaporator, the air enters the heater and air conditioner selector duct assembly where, by means of diverter doors, it is caused to pass through or to bypass the heater core in the proportions necessary to provide the desired outlet temperature . Then conditioned air enters the vehicle through either the floor distributor duct or the dash outlets . During cooling operations, the air is cooled by the evaporator to below comfort level, it is then warmed by the heater to the desired temperature . During "heating only" operations, the evaporator will not be in operation and ambient air will be warmed to the desired level in the same manner. The diverter doors which direct the air flow through this system are operated by the vacuum motors. The A/C control unit is positioned between the vacuum source and the motors to direct the application of vacuum as required . 2-2 SECTION 2 - HEATING AND AIR CONDITIONING THERMOSTATIC EXPANSION VALVE ELECTROMAGNETIC CLUTCH "HP V" 7n THERMOSTATIC SWITCH RECEIVERDEHYDRATOR CONDENSER EVAPORATOR COMPRESSOR "HPL" J DESICCANT BAG "LPV" "LPL" LIQUID LINE "LPV/Ipl" P-SERIES EXPANSION TUBE (ORIFICE) ELECTROMAGNETIC / CLUTCH PRESSURE CYCLING SWITCH "HPV" . r CONDENSER COMPRESSOR "HPL" "LPL" LIQUID LINE OIL BLEED HOLE "LPV/I I" DESICCANT BAG G-SERIES HPV HPL LPV LPL - HIGH-PRESSURE VAPOR HIGH-PRESSURE LIQUID LOW-PRESSURE VAPOR LOW-PRESSURE LIQUID Figure 2-2 - Basic Air Conditioning System - Refrigeration Schematic 2-3 SECTION 2 -- HEATING AND AIR CONDITIONING P-SERIES SYSTEM Operational Quick Checks This system performs the cooling functions only. When heating (above ambient temperatures) is desired, the vehicle heater must be used . The following checks may indicate if the amount of refrigerant (charge) in the system is low . The ambient temperature must be above 70°F. This self-contained unit is bracket mounted to the dash by the motor home manufacturer . It operates on inside (recirculated) air only. Air is drawn into the unit, passed through the evaporator core (receiving maximum cooling) and then directed into the vehicle through adjustable outlets . NOTE: Engagement of the compressor clutch in both of the tests below indicates that the clutch electrical circuit is O.K. If the clutch does not engage, then check for a blown fuse, loose connections or damaged or deteriorated wires. If these checks are O.K., then the problem may be in the compressor clutch or switch. Take the vehicle to a qualified shop for further testing. A thermostatic switch, located on the face plate is used to control compressor operation by sensing air temperature as it leaves the evaporator core. G-SERIES 1 . Prepare the motor homes as follows : Engine must be warm (CHOKE OPEN and OFF FAST IDLE SPEED CAM) and at normal idle speed. Hood and body doors open . Selector (mode) lever set at NORM. Temperature lever at COLD. " Blower on HI . MAINTENANCE AND INSPECTION There are two sections to the air conditioning system . The first section includes the refrigeration components-compressor, condenser, evaporator, etc . The second section includes the air distribution components such as the blower, case assembly, diverter doors, vacuum lines and motors, etc . 2. With the compressor engaged, place your hand first on the evaporator inlet pipe (between the expansion orifice and evaporator), and then on the accumulator can surface (Figure 2-3) . " The temperature should feel the same for both and somewhat cooler than the ambient temperature . If the inlet pipe feels cooler than the accumulator surface, the system's refrigerant charge is probably low . Maintenance and inspection procedures are directed to each of these sections . Of course, for the P-Series, the air distribution section is quite simple and does not include the many components used in the G-Series . REFRIGERATION SECTION CAUTION : BECAUSE OF THE NATURE OF REFRIGERANT-12 AND THE HIGH PRESSURES WHICH ARE PRESENT IN THE REFRIGERANT SECTION OF THE SYSTEM, PERSONAL INJURY CAN RESULT IF ESTABLISHED DIAGNOSTIC AND SERVICE PROCEDURES ARE NOT FOLLOWED . THEREFORE, ALL SUCH WORK REQUIRED ON THE SYSTEM SHOULD BE REFERRED TO A QUALIFIED SHOP WITH THE NECESSARY TRAINED PERSONNEL AND EQUIPMENT . THE FOLLOWING PROCEDURES ARE INTENDED TO IDENTIFY OR AVOID POTENTIAL PROBLEM CONDITIONS. Inspection Perform the following checks regularly : 1 . Check outer surfaces of radiator and condenser cores to be sure they are not plugged with dirt, leaves or other foreign material . Be sure to check between the condenser and radiator as well as the outer surfaces. 2. Check the metal tubing lines to be sure they are free of dents or kinks which can cause a loss of system capacity due to a line restriction . 3. Check the flexible hose lines for brittleness or deterioration which could cause a system leak. 4. Check for proper drive-belt tension . Figure 2-3 - Checking Evaporator Inlet and Accumulator Temperatures (G-Series) P-SERIES (WITH SIGHT GLASS) At temperatures higher than 70°F, the sight glass may indicate whether the refrigerant charge is sufficient . A shortage of liquid refrigerant is indicated after about five minutes of compressor operation by the appearance of slow-moving bubbles (vapor) or a broken column of refrigerant under the glass. Continuous bubbles may appear in a properly charged system on a cool day. This is a 2-4 SECTION 2 HEATING AND AIR CONDITIONING normal situation . If the sight glass is generally clear and performance is satisfactory, occasional bubbles do not indicate a refrigerant shortage. should be replaced . If the hoses are O.K ., the problem may be in the control assembly or vacuum motor(s). Take the vehicle to a qualified shop for further testing . If the sight glass consistently shows foaming or a broken liquid column, it should be observed after partially blocking the air to the condenser . If under this condition the sight glass clears and the performance is otherwise satisfactory, the charge shall be considered adequate . OPTIONAL AIR CONDITIONING SYSTEM NOTE: The sight glass is located on or near the receiverdehydrator . AIR DISTRIBUTION SECTION Electrical Circuit Diagnosis The blower electrical circuit and motor are O.K. if the blower operates at all of the designated speeds . If the blower does not work at all, then check for a blown fuse, loose connections, and for damaged or deteriorated wires . If these checks are O.K. and/or the blower does not operate at all speeds, then the problem may be in the switch, relay or motor. Take the vehicle to a qualified shop for further testing . Vacuum System Diagnosis (G-Series) If the air is not flowing through the proper outlets (floor, dash, or defroster), then there may be a problem in the vacuum system, or with the diverter doors. Check the doors to see that they operate properly and do not bind. Next, check all vacuum hoses and connections between the vacuum source, A/C control and vacuum motors for leaks. If any hoses are damaged or deteriorated, they The factory installed air conditioning system has made several changes since first made available in the 1986 Class A chassis. The next several pages attempt to assist with part numbers and description of the items installed by Chevrolet or the coach builder. Only parts of the A/C system are installed on the chassis as the coach body is installed by the coach builder whose responsibility is to complete the system including proper charging with freon and' wiring system to insure proper operation . Those items not listed with part numbers are installed by the coach builder . 1986 thru mid year 1989, A/C systems and repair parts were provided by ARA Manufacturing Co. i n Grand Prairie, TX. However, they are out of business and their surplus parts were sold to Acme Radiator and A/C Inc ., 17103 State Road 4 East, Goshen, IN 46526, Phone (219) 534-1516 . 1989 to present the parts are provided by Wynns Inc . and most parts can be obtained through the General Motors dealers . Assistance for NPN Wynns parts can be obtained by calling 1-800-347-3883 1900 S.E. loop 820, Ft. Worth, TX 76140. APPENDIX 2-1 OPTIONAL AIR CONDITIONING SYSTEM For 1986, at the request of several RV manufacturers, GM has made available the underhood portion of the air conditioning system as an available option' - Option Number 7N4. GM can, as ordered, produce the engine mechanical air conditioning parts, as furnished by ARA Manufacturing Company. . 2 The following illustrations and part number listings (both GM production numbers and corresponding ARA part numbers) are provided as an aid to the motor home owner concerning installation, repair and replacement of air conditioning system Option Number 7N4 . This system became standard start-of-production 1988. (See NOTE on page 2-7 .) . _ 18 - 5 0 0 G H I o No. 1 2 3 4 5 6 7 ARA PART NO. 7045871 7045872 7045873 7045833 7045824 5004112 1502902 A. NOTE: SEE APPENDIX A - DRIVE BELTS AND TENSION SPECIFICATIONS FOR GM BELT NUMBERS MOUNT AND DRIVE ASSEMBLY PARTS UST DESCRIPTION QUANTITY Compressor Mount 1 Compressor Mount Support 1 Compressor Brace 1 Compressor Adjusting Arm 1 Compressor Adjusting Block 1 Idler Spacer, 1-3/8" Long 1 Carton 1 Bolt Kit. Consisting of : (1) 1/4" x 4" NC (AI Thread) Bolt (1) 3/8" x 5-1/4" NC Bolt 8 7004312 (2) 3/8" x 7/8" NC Bolt (1) 1/4" Flatwae 1 (3) 3/8" x 1-1 /2" NC Bolt (8) 3/8" r (3) 3/8" x 1-3/4" NC Bolt (6) 3/8" (SAE) Flatwasher (1) 3/8" x 4-1/4" NC Bolt _ (1) 3/8" NC Hex Nu 9 5001018 Idler Spacer, 9/16" Long (Required on vehicles with single Air Injection Pump) Compressor No . 709 "Sanden" 10 0329174 1 Clutch, 5-1/4" Diameter NOTE : The following parts are all listed under the GM Part No . 14100875 : Compressor Adjusting Block Idler Spacer, 1-2/8" Long Bolt Kit. Consisting of: (See Above Listing) Figure A2-1-1 -Chevrolet Motor Home Chassis Compressor Assembly 2-6 , I GM PROD . NO . (14100871) (14100872) (14100873) (14100874) (14100875) (14100875) (14100875) (15578925) APPENDIX 2- 1 OPTIONAL AIR CONDITIONING SYSTEM GM RETRO-FIT "A" CHASSIS EVAPORATOR ASSEMBLY EVAPORATOR COIL ' * FUSE BOX LIQUID __ HOSE * CONDENSER EXPANSION FAN HARNESS VALVE ELECT RELAY REAR DISCHARGE COMPRESSOR DISCHARGE HOSE SUCTION HOSE FAN RELAY " II*III* I HEATER CORE NIPPLES q I - I HEATER HOSES I _ I I _ SWITCH CONNECTOR ' , DENOTES PARTS FURNISHED WITH EVAPORATION KIT INSTALLED . BY RV MANUFACTURER I °' 1111 PART OF GM OPTION NO. 7N4 (PRE-1988 UNITS) NOTE: AIR CONDITIONING SYSTEM DESCRIBED ABOVE BECAME STANDARD EQUIPMENT WITH START OF PRODUCTION 1988, EXCEPT WHEN UNIT WAS ORDERED AND BUILT WITH OPTION - AIR CONDITIONING DELETE, AS INDICATED ON THE SERVICE PARTS IDENTIFICATION LABEL (SEE PAGE 1-3). THIS SITUATION WOULD REQUIRE THE MANUFACTURER TO INSTALL THEIR OWN AIR CONDITIONING SYSTEM . BASIC CHANGE FOR INTERIM 1990 MODEL IS USE OF ONE 16 INCH FAN REPLACING TWO 10 INCH FANS STARTING 11-13-89. _ No. 1 CONDENSER ASSEMBLY PARTS LIST ARA PART NO. 0519336 1 0519406 2 0570689 3 0884940 DESCRIPTION 1985-1/2 Condenser Assembly without engine oil cooler 1987 to Current Condenser Assembly with engine oil cooler in bottom (Shown above) Mtg. Hardware, Consisting of Screw #14 x 3/4 HWH Z/P D/P Switch, Coolant Temperature QUANTITY (15547181) 1 (15578281) 10 1 Figure A2-1-2 - Chevrolet Motor Home Chassis Condenser Assembly 2-7 GM PROD . NO. 1 (15547201) APPENDIX 2- 1 OPTIONAL AIR CONDITIONING SYSTEM (Cont'd) 19 18 11 23 16 17 I \, 25 6 7 24 26 5 ,. 15 22 16 6 No . ARA PART NO. '1 . 0519369 2 1273235 3 0319606 4 1900157 5 0039851 6 0319647 7 0996400 8 0058337 9 0543513 10 0059605 11 0059606 12 0059706 13 0964045 14 1701620 15 1016434 16 0319387 17 1016433 18 0986195 19 0548325 20, 0049849 21 0876802 22 0319563 23 0039852 24 0039853 25 0039855 26 0039854 to 5 2 15 9 8 13 3 4 15 CONDENSER KIT PARTS LIST (without Oil Cooler) DESCRIPTION Coil Condenser Receiver-Drier Bracket, Mounting Receiver-Drier Sticker, Caution Screw, #8 x 1/2 HWH Bracket, Condenser Mounting Grommet-Condenser Mt Brkt Ground Wire Coupling-Receiver Drier 'O' Ring-Receiver Drier Outlet 'O' Ring #6-Receiver Drier Inlet 'O' Ring Valve H ose 'O' Ring Valve Ca Condenser Fan Assy . Guard, Fan Seal, Condenser Fan Bracket, Condenser Seal Mounting Seal, Condenser to Radiator Hose, Discharge #8 Service Valve, Discharge Cap, Aluminum Terminal, Adapter Bracket, Adapter Bolt, 1/4-20 x 5/8" HH ZIP Lockwasher, Star 1/4" ZIP Lockwasher, 1/4" ZIP Starwasher #10 - QUANTITY 1 1 1 1 20 2 1 1 1 1 2 1 2 2 4 2 2 1 1 1 1 2 8 1 7 1 GM PROD . NO. 15547181 15547182 15547188 15547189 15547190 15547183 15547184 15547185 15547186 15547187 15547191 15547193 15547194 15547195 15547196 15547198 15547199 15547200 15547197 15547669 Figure A2-1-3 - Chevrolet Motor Home Chassis Condenser Kit -Without Engine Oil Cooler (19851 /2 -1987) 2-8 APPENDIX 2-1 OPTIONAL AIR CONDITIONING SYSTEM ' 6 2019 7 6 16 i 17 17 4 8 15 NO. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 9 I, 18 13 II 3 5 2 27 l I( 28 1 ARA PART NO. 0519405 1273235 0058337 0543513 0059605 0059606 0559607 0319606 0320184 0996400 0964045 0964040 1701620 1016434 1900157 0319387 1016433 0876802 0986306 0548325 0049849 0543516 0039851 0319563 1120235 0320185 0409443 0022151 0049887 14 16 29 26 24 11 14 25 14 12 13 23 CONDENSER KIT PARTS LIST (with Oil Cooler) DESCRIPTION Coil Condenser Receiver-Drier Fitting, Self Sealing O Ring Special O Ring #6 O Ring #8 O Ring #10 Bracket, Receiver-Drier Mounting Bracket Condenser Fan Mounting (Upper) Grommet Lavelle #917 Condenser Fan and Seal Assembly Blade Fan Fan Guard Seal, Fan/Condenser Caution Label Bracket, Condenser Seal Mounting Seal, Condenser to Radiator Terminal Adapter Hose, #8 Discharge Service Valve Discharge Cap, Aluminum #8 Screw, #8 x 1/2" HWH Z P Bracket, Adapter Motor, DC Bracket, Condenser Fan Mounting Lower Hose Clam 1/2" Bolt, 1 4 20 x 5/8" HH Shipping Cap QUANTITY 1 1 1 1 1 2 1 1 1 1 2 2 2 4 1 2 2 1 1 1 1 2 20 2 2 1 1 8 2 GM PART NO . 15578281 15547182 15547183 15547184 15547185 15547186 15547187 15547188 15578282 15547190 15547191 15583108 15547193 15547194 NCSI 15547195 15547196 15547197 15584784 15547199 15547200 14055585 15547360 15581669 15583107 15578283 Figure A2-1-4 - Chevrolet Motor Home Chassis Condenser Kit -With Engine Oil Cooler (1988 -1991) 2-9 APPENDIX 2-1 AIR CONDITIONING SYSTEM NO . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 CONDENSER KIT PARTS LIST with 011 Cooler PART NO. 0519557 1273235 0058337 0543513 0059605 _005_9606 0559607 0319606 0321934 0996500 0964045 0964115 1701620 1016434 1900157 0319387 1016433 0876802 0986307 0548325 0049849 0039851 0319563 N55 see 12 0321935 0986968 0986967 DESCRIPTION Coil Condenser Receiver-Drier Fitting, Self Sealing 0 Ring Special 0 Ring #6 0 Ring #8 0 Ring #10 Bracket, Receiver-Drier Mounting Bracket Condenser Fan Mounting (Upper) Grommet Lavelle #917 Condenser Fan and Seal Assembly 16" Fan Assembly Fan Guard Seal, Fan/Condenser Caution Label Bracket, Condenser Seal Seal, Condenser to Radiator Terminal Adapter Hose, #8 Discharge Service Valve Discharge Cap, Aluminum Screw, #8 x 1/2" HWH Z P Bracket, Adapter Motor, DC Bracket, Condenser Fan Mounting (Lower) Inlet Tube Outlet Tube O Ring #8 QUANTITY 1 1 1 1 1 2 1 1 1 1 2 2 2 4 1 2 2 1 1 1 1 20 2 2 1 1 1 4 Figure A2-1-5 - Chevrolet Motor Home Chassis Condenser Kit - With Engine Oil Cooler (1990 Interim) 2-10 APPENDIX 2-1 OPTIONAL AIR CONDITIONING SYSTEM (Cont'd) GM PART NO . 15604813 ARA P/N 0986421 HOSE, OIL COOLER OUTLET GM PART NO . 15604811 ARA P/N 0986420 HOSE, OIL COOLER INLET GM PART NO . 14055585 ARA P/N 0543516 RINGS (2) GM PART NO . 15578281 ARA P/N 0519406 CONDE14SER ASSEMBLY WITH ENGINE OIL GM SUPPLIED HOSE CLAMPS (2) GM SUPPLIED BOLTS (2) OIL HOSES FROM ENGINE, GM PART NO . 14055585 ARA P/N 0543516 "O" RINGS (2) / NOTE : Interim 1990 will have metal lines 1988-1989. Figure A2-1-6 - Chevrolet Motor Home Engine Oil Hose Kit 2-11 LOWER RADIATOR SUPPORT APPENDIX 2-1 OPTIONAL AIR CONDITIONING SYSTEM (Cont'd) DK. BLUE/RED HARNESS SYSTEM PART NOS . 0885033, 0885132, AND 6499142 RED RED BLACK/WHITE STARTER SOLENOID COOLANT TEMPERATURE DK. BLUE SWITCH LOCATED IN LEFT TANK OF RADIATOR Of 30 AMP FUSE DK. BLUE RED DK. BLUE/RED TO A/C CONTROL PANEL HARNESS (DK . BLUE/RED) + HOT W/IGN. ON DK. BLUE/WHITE NORMALLY OPEN., CLOSES TO GROUND AT 221 °F APPROX . GROUND UE SWITCH BLACK/WHITE NORMALLY OPEN . CLOSES TO GROUND AT 225 PSI . REFRIGERANT PRESSURE GROUND CONDENSER FANS * NOTE: Wiring shown is not supplied or installed by GM through 1990. Shown as an aid to the technician as typical of manufacturers' installations of wiring purchased from ARA . NOTE: Starting with the 1991 Class A motorhome, the A/C condenser fan is wired by Chevrolet through the main front end engine wiring harness . The coolant temperature switch is now located in the RH cylinder head with a green wire. NOTE: Dual 10" fans are standard with Chevrolet installed A/C from 1986 through interim 1990. Interim 1990 changes to one 16" fan November 13, 1989. VIN L3315231 Figure A2-1-7 - Typical ARA Wiring Diagram - Class "A" RV Condenser with Fans APPENDIX OPTIONAL AIR CONDITIONING SYSTEM (Cont'd) A/C CONDENSER & BLOWER MODULE ASSEMBLY RADIATOR LOWER MOUNTING PANEL (138) Effective 11-13-89 VIN 11-3305628 Condenser #15643270 Metal Lines 14054378 14054379 Interim 1990 Inlet Hose 15557762 Outlet Hose 15557765 Fittings 14055586 Figure A2-1-8 - Oil Cooler Lines P300 (32 52) & L19 & Env. APPENDIX OPTIONAL AIR CONDITIONING SYSTEM 1991 P3(32) ENGINE OIL COOLER (WIL1917 .4N & A/C) 4 (32) NOTE: QUANTITY IS ONE PER VEHICLE UNLESS OTHERWISE SPECIFIED . Figure A2-1-9 - 1991 P3(32) Engine Oil Cooler 1. 2. 3. 4. 5 6. 7. 8. 9. 10. N .S. 3.430 1 .540 8.900 1 .540 1 .540 1 .540 1 .540 1.540 1 .540 1 .540 9.190 8.977 CONDENSER, A/C (P3 32 W/7 .4N)('1) SINGLE FAN 1990-1992 . . . . . BOLT, W/CON WA, HEX (P3 32 W/7 .4N)(AS REQD) . . . . . . . . . . . . . . BRACKET, ENGINE OIL COOLER HOSE (P3 32 MAN) . . . . . . . . . . . . . . BOLT, HFH (M8X1 .25X18)(AS REQD) . . . . . . . . CONNECTOR, ENGINE OIL COOLER HOSE (P3 . . 32 . . W/7 . . . .4N) . . . .. . . . .. .. FITTING, ENGINE OIL COOLER HOSE (P3 32 MAN) . . . . . . . . . . . HOSE, ENG OIL COOLER INLET (P3 32 MAN & ENV, EXC EN2) . . HOSE, ENG OIL COOLER INLET (P3 32 W/7AN & EN2, EXC ENV) . . HOSE, ENG OIL COOLER OUTLET (P3 32 MAN & ENV . EXC EN2) HOSE, ENG OIL COOLER OUTLET (P3 32 W/7 .4N & EN2, EXC ENV) CLIP, ENGINE OIL COOLER HOSE (P3 32 W/7 .4N)(AS REQD) . . . . . BOLT, W/LOCKWASHER A/C EVAP & BLO MDL (AS REQD) . . . . . . SCREW, W/FLAT WASHER, HEX TAP (M3X1AX16)(AS REQD) . . . DEFINITIONS - A/C ENGINE PROVISIONS - EXC A/C . . . . . . . . . . . . . . . . .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15643270 . . . . . . . . . . . 3997227 14054335 . . . . . . . . . . 12337905 .. .. .. .. .. .. .. .. .. .. 15654938 . . . . . . . . . . 15538480 . . . . . . . . . . 15638189 . . . . . . . . . . 15638187 . . . . . . . . . . 15638190 . . . . . . . . . . 15638188 . . . . . . . . . . 15517986 . . . . . . . . . . 14030698 . . . . . . . . . . 11509371 APPENDIX 2-4 OPTIONAL AIR CONDITIONING SYSTEM (Cont'd) 1991-1992 P3(32) ENGINE OIL COOLER (L1917.4N)(WIC60) NOTE: QUANTITY IS ONE PER VEHICLE UNLESS OTHERWISE SPECIFIED . TP01-313 Figure A2-1-10 - 1991-1992 P3(32) Engine Oil Cooler 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11 . 12. 13. 14. 1.540 8.900 1 .540 1 .540 1.540 1.540 1 .540 1 .540 1 .540 1 .540 8.900 8.950 9.220 8.950 N .S. 8.977 BRACKET, ENGINE OIL COOLER HOSE (P3 32 W/7 .4N) . . . . . . . . . . . . . . . . BOLT, HFH (M8X1 .25X18)(AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CONNECTOR, ENGINE OIL COOLER HOSE (P3 32 W/7 .4N) . . . . . . . . . . . . FITTING, ENGINE OIL COOLER HOSE (P3 32 W/7 .4N) . . . . . . . . . . . . . . . . . HOSE, ENGINE OIL COOLER INLET (P332 W/7.4N & ENV . EXC EN2) . . . . . HOSE, ENGINE OIL COOLER INLET (P3 32 W/7.4N & EN2, EXC ENV) . . . . . HOSE, ENGINE OIL COOLER OUTLET (P3 32 W/7.4N & ENV . EXC EN2) . . . HOSE, ENGINE OIL COOLER OUTLET (P3 32 W/7 .4N & EN2, EXC ENV) . . . CLIP, ENGINE OIL COOLER HOSE (P3 32 W/7 .4N)(AS REQD) . . . . . . . . . . . TUBE, OIL COOLER INLET (P3 32 W/7 .4N & C60) . . . . . . . . . . . . . . . . . . . . . BOLT, HEX (5/16-18X3/4)(AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CLAMP, LOOP CUSHIONED (AS REQD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . TUBE, AIR CONDITIONER OUTLET (P3 32 W/7 .4N & C60) . . . . . . . . . . . . . . STRAP, METRIC PLASTIC ADJUSTABLE TIE (215MM LENGTH)(AS REQD) CONDENSER, AIR CONDITIONER (P3 32 W/7 .4N)(*1) . . . . . . . . . . . . . . . . . SCREW, W/FL WASHER, HEX TAP (M6.3X1 .8X16)(AS REQD) . . . . . . . . . . . . NOTE 1 : SEE ILLUSTRATION IN 9.000 FOR FURTHER DETAILS . RPO DEFINITIONS C60 - AIR CONDITIONER FRONT, MANUAL CONTROLS ENV - AIR CONDITIONING ENGINE PROVISIONS EN2 - AIR CONDITONING, DELETE 2-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14054335 11513703 15654938 15538480 15638189 15638187 15638190 15638188 15517986 15665135 . 9440967 . 2041644 15665136 11501906 15687269 11509371 APPENDIX 2-5 OPTIONAL AIR CONDITIONING SYSTEMS (Cont 1d) 1994 AIR CONDITIONING THE GOOD AND BAD OF CFCs When R-12 (often referred to by its brand name Freon) was introduced in 1930, the industry hailed it as a miracle chemical . It was non-poisonous, easy and cheap to manufacture and quite stable. The first in the family of chlorofluorocarbons (CFCs) yet to come, R-1 2's apparent stability and low cost made air conditioning the creature comfort of the 20th century. Of all the R-12 manufactured, about twothirds is used to service automotive air conditioners . Unfortunately, recent scientific findings prove that we may have a big price to pay in the future for the comfort we've enjoyed in the past. The findings show that CFCs, like R-12 are depleting the Earth's protective ozone layer located in the stratosphere some 10 to 30 miles above the planet's surface . This precious layer of ozone filters out most of the sun's harmful ultraviolet rays. THE CLEAN AIR ACT AMENDMENTS OF 1990 The most important part of the amendments to Section 609 of the Federal Clean Air Act have to do with servicing motor vehicle air conditioning and technician certification . The act states : Servicing Motor Vehicle Air Conditioners - Effective January 1, 1992, no person repairing or servicing motor vehicles for consideration may perform any service on a motor vehicle air conditioner involving the refrigerant for such air conditioner without properly using approved refrigerant recycling equipment and no such person. may perform such service unless such person has been_ properly trained and certified . R134A REFRIGERANT The change to R1 34A will be effective with the 1994 model chassis beginning in August 1993. The changes that are required to accept this new refrigerant on factory installed components on the P30 motor home chassis will affect those components added by your coach builder to complete the system . SYSTEM DIFFERENCES 1 . Condenser a. Width and Height the same b. Thickness changes from 1 .4" to 1 .85" c . Inlet and outlet fittings - metric thread d. Service valve-located at condenser inlet instead of compressor e. Will be PRECHARGED f. Wynn's climate system . 2. A/C Compressor a. Lubricating oil is different than R-12 Systems . Oil used is Sanden SP-20 (GM part #15959132). b. Plumbing connections are clamp on, rather than threaded to prevent intermixing R-12 compressors and R-1 34A compressors . 3 . A/C Plumbing a. The liquid line, from the receiver drier to the evaporator will be provided by the body builder. The receiver drier end of the line will have a metric quick connect fitting. b. The suction line from the evaporator to the compressor will be provided by the body builder. The compressor fitting end of the hose will have to match . This fitting is currently manufactured by S&H Fabricating, Walled Lake, Michigan . The line must be equipped with a quick connect gauge fitting . 4. A/C Evaporator a. The evaporator outlet must be equipped with a suction service valve similar in arrangemenht to the condenser discharge line. GENERAL INFORMATION 1 . Dedicated equipment is required to recycle, evacuate, and charge R-134A Systems . Do Not mix R-12 and R-1 34A . Contamination and damage to your coach will result. 2. It requires a different desiccant and higher system pressure and more airflow across the condenser. 3. GM approves only the following A/C hoses and tube suppliers for our vehicles. This is based on extensive lab tests which include pressure and temperature cycling, vibration tests, and moisture ingression testing, and field trials in car and truck fleets across the country. These suppliers are familiar with all the GM fitting designs, testing requirements, etc . Only two hoses, are GM approved for use with R-134a . They are Parker P-90 Hose and Goodyear 4680 Hose. The coupling suppliers are : APPENDIX 2-5 S&H Fabricating Walled Lake, Michigan (313) 624-1661 Fayette Tubular Products Fayette, Ohio (419) 237-2531 Parker Automotive Products Cleveland, Ohio (216) 531-3000 4. The A/C Compressors are shipped from the factory with the proper oil charge for the system . 5. You should expect the identical performance from your R-1 34A System as your old R-12 System . A/C Compressor L19 Gas #15680077 Sanden L65 Diesel #1136400 Harrison SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES FRONT ALIGNMENT GENERAL DESCRIPTION The term "front alignment" refers to the angular relationships between the front wheels, the front suspension attaching parts and the ground . The pointing in or "toe-in"'of the front wheels, the tilt of the front wheels from vertical (when viewed from the front of the vehicle) and the tilt of the suspension members from vertical (when viewed from the side of the vehicle), are all involved in front alignment. CASTER Caster is the tilting of the front steering axis either forward or backward from the vertical (when viewed from the side of the vehicle) . A backward tilt is said to be positive (+) and a forward tilt is said to be negative (-). (See Figure 3-1 .) CAMBER Camber is the tilting of the front wheels from the vertical CENTERLINE OF VEHICLE when viewed from the front of the vehicle. When the wheels tilt outward at the top, the camber is said to be positive (+). When the wheels tilt inward at the top, the camber is said to be negative (-). The amount of tilt is measured in degrees from the vertical and this measurement is called the camber angle . (See Figure 3-1 .) TOE-IN Toe-in is the turning in of the front wheels . The actual amount of toe-in is normally only a fraction of an inch . The purpose of a toe specification is to ensure parallel rolling of the front wheels . (See Figure 3-1 ;) Toe-in also serves to offset the small deflections of the wheel support system which occur when the vehicle is rolling forward. In other words, even when the wheels are set to toe-in slightly when the vehicle is standing still, they tend to roll parallel on the road when the vehicle is moving . It should be noted that excessive toe-in or toe-out will cause tire wear . CENTERLINE OF WHEEL POSITIVE CAMBER WHEEL TILTS OUTWARD AT TOP AS SHOWN e NEGATIVE CAMBER WHEEL TILTS INWARD 90° AT TOP FRONT POSITIVE DIRECTION NEGATIVE CASTER - AXIS TILTS FORWARD AT TOP POSITIVE DIRECTION CAMBER ANGLE FRONT VIEW CASTER ANGLE SIDE VIEW WHEEL TOE-IN TOP VIEW Figure 3-1 - Caster, Camber and Toe-in CENTERLINE OF WHEEL 1-.,-CENTERLINE OF BALL JOINT AXIS POSITIVE CASTER AXIS TILTS BACK AT TOP AS SHOWN SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES MAINTENANCE AND INSPECTION CHECK RIDE HEIGHT MEASUREMENT (REFERRED TO AS EITHER DIMENSION "A" OR "BC") BETWEEN BRACKET AND CROSS MEMBER FLANGE . MEASUREMENT MUST BE PERPENDICULAR TO CROSS MEMBER FLANGE. MEASUREMENT IS "IRON TO IRON." RUBBER BUMPER IS NOT INCLUDED. There are several factors which can affect front alignment . These factors include tire inflation pressures, the condition of wheel bearings, steering and suspension components. They are the basis for the following checks which can indicate problems that should be corrected . 1 . Check all tires for proper inflation pressures and approximately the same tread wear. 2. Check front wheel bearings for looseness . 3. Check for looseness of ball joints, tie rod ends and steering relay rods and damper. LOWER CONTROL ARM BRACKET 4. Check for excessive run-out of wheels and tires. 5. Check for a difference in the ride height between right and left sides of the vehicle . (See Figure 3-2 .) NOTE : Excessive or unevenly distributed loads also affect ride height and alignment . This should be taken into consideration when making the check. Also, if the motor home is equipped with air bag cylinders, it is important that the cylinders be inflated to the proper pressure for the load being carried, in order to maintain adequate ride height. (See Air Bag Cylinder Inspection information in the Suspension section of this manual .) Figure 3-2 - Ride Height Measurement 8. Check for loose control arms. 9. Check for loose or missing stabilizer bar attachments . 6. Check for steering gear looseness at frame. 10. Steering and vibration complaints are not always the result of improper alignment . An additional item to be checked is the possibility of tire lead due to worn or improperly manufactured tires. "Lead" is the deviation of the vehicle from a straight path on a level road without hand pressure on the steering wheel. Tire balance should also be checked . 7. Check for improperly operating shock absorbers . There may be evidence of a leaking shock(s) . NOTE: Alignment should be done with the unit fully loaded . WHEEL ALIGNMENT SPECIFICATIONS - CASTER DIMENSION "A"/"BC" (IN .) 1-1/2 1-3/4 2 2-1/4 2-1/2 2-3/4 3 3-1/4 3-1/2 3-3/4 G-10, 20 3-1/2° 3-1/4° 3° 3° 2-3/4° 2-1/2° 2-1/4° 2° G-30 2-3/4° 2-1/2° 2-1/4° . 2° 1-1/2° 1° 3/4° 1/2° P-20, 30 3° 2-1/2° 2-1/4° 2° 1-3/4° 1-1/2° 1-1/4° MOTOR HOME 5-1/2° 5-1/4° 5° 4-3/4° 4-1/2° (32) MODEL G10, 20 G30 MOTORHOME (32) CAMBER TOE-IN (IN .) .5° .2° 3/16 0.1 0 4 4-1/4 4-1/2 4-3/4 2°, 1/4° 1° 1-3/4° 1-1/2° -1/40 1/2° 1/4° 0° 4° 3-3/4° 3-1/2° 3-1/4° 3° 0° 1/2° 5 3° 1-BEAM AXLE (OPTION FS3) 3/16 3/64 ± 1/64'" '~ Toe-in was reduced from 5/16 inch in 1985 as part of a GM trend reducing toe-in. If equipped with radial tires, some tire manufacturers would suggest toe-in specifications of 1/32 inch to 1/8 inch . NOTE: 60 minutes equal 1 degree . TOE-IN (IN .) 3/16 t 1/16 CASTER'` +2-1/2 0 f 1/2 0 CAMBER +1-1/2° t 1/2° KING PIN INCLINATION (NOT ADJUSTABLE) 70 10" Refer to Frame Angle Measurement Information in this section of the manual for correction to caster procedure . Figure 3-3-Alignment Specifications 3-2 SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES ALIGNMENT CHECK The caster, camber and toe-in specifications for both the G- and P-Series chassis are shown in Figure 3-3 . The caster specifications will vary depending on the ride height measurement shown in Figure 3-2 . This measurement is commonly referred to as either Dimension "A" or Dimension "BC" depending upon your reference source . This dimension is also affected by rear axle imbalance of weight (left to right) . See Rear Suspension section of this manual for further information . Another factor which will affect the caster measurement is the frame angle (Figure 3-4) . Frame angle should be taken into account when determining the proper caster setting . 4. Determine the caster setting following the procedures in the appropriate shop manual . 5. Compute the actual caster setting from the frame angle and caster measurement taken as follows : (a) A down-in-rear frame angle must be subtracted from a positive caster specification . (b) An up-in-rear frame angle must be added to in the appropriate shop manual. (c) A down-in-rear frame angle must be added to a negative caster . specification. (d) An up-in-rear frame angle must be subtracted from a negative caster specification . LOWER BALL JOINT INSPECTION Lower ball joints are a loose fit when not connected to the steering knuckle . Wear may be checked without disassembling the ball stud, as follows : 1 . Support weight of control arms at wheel hub and drum . 2. Accurately measure distance between tip of ball stud and tip of grease fitting below ball joint. 3. Move support to control arm to allow wheel hub and drum to hang free. Measure distance as in Step 2. If the difference in measurements exceeds 2.38 mm (.094 or 3/32 inch) for all models, the ball joint is worn and should be replaced . (See Figure 3-5 .) Figure 3-4 - Frame Angle Measurement FRAME ANGLE MEASUREMENT To determine the frame angle: 1 . Park the motor home on a level surface . 2. Place a protractor with a level gage against the bottom of a straight section of the frame rail near the chassis midpoint . 3. Determine the angle the frame rail slopes from level. NOTE: Determine if the vehicle has either an up-in-rear measurement or a down-in-rear measurement . Figure 3-5 - Lower Ball Joint Check SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES STEERING SYSTEM The steering system consists of the steering linkage, steering gear, steering pump; hoses, and the steering column and wheels . Vehicle direction is controlled from the steering wheel. Rotating the steering wheel rotates the input shaft (wormshaft) on the steering gear by means of a shaft in the steering column . Rotation of the wormshaft transfers this motion to the output shaft of the steering gear. The output shaft of the gear controls the directional position of the front wheels (right or left depending on input) through a series of arms or levers referred to as the steering linkage . A damper incorporated into the linkage helps to control the road shock transmitted to the linkage from the wheels . STEERING LINKAGE GENERAL DESCRIPTION The steering linkage is located forward of the front cross member. The P-Series linkage is illustrated in Figure 3-6 . Steering effort is transmitted to left- and right-hand adjustable tie rods through a relay rod . The relay rod is connected to an idler arm on the right and to the pitman arm on the left. P-SERIES SUPPORT ASSEMBLY MAINTENANCE AND INSPECTION LUBRICATION OF STEERING LINKAGE The steering linkage under normal conditions should be lubricated with any water-resistant EP-type chassis lubricant every 7,500 miles or six months, whichever occurs first. Lubricate every 3,000 miles or two months whichever occurs first when operating in dusty or muddy conditions, or if the vehicle is used "off-road ." STEERING LINKAGE, SUPPORT ASSEMBLIES (P-SERIES) The fit of the shafts in the linkage support assemblies (Figure 3-6) should be tight with end play not exceeding .003 inch . Check the end play. If the end play exceeds .003 inch in either assembly, adjust it to within 0 to .003 inch . Loosen large lock nut torque cap to 25' Ibs.and then loosen 1/16 turn and tighten lock nut . If there is side play, replace the bushings (GM Part No. 266316) in the affected assembly . STEERING DAMPER CHECK The type of steering damper shown in Figure 3-7 is nonadjustable, nonrefillable and is not repairable. At each lubrication interval, perform Check No. 1 and No . 2 on the steering damper system . Check 1 Check the damper attachments to be sure they are properly and securely installed . (Tighten, if loose.) The damper assembly should be replaced if the rubber bushings are badly worn . Check 2 Inspect the damper for evidence of fluid leakage . A light film of fluid is permissible on the body of the damper near the shaft seal. A dripping damper should be replaced . Check 3 Turn the steering wheel so as to extend the piston rod from the damper body. If the piston rod is rusted badly, replace the damper. If rust is light, clean the rod . Use care so that the rod surface is, not damaged . * ADJUSTMENT: End Play should be 0 to .003 inch . Side-to-side clearance requires bushing replacement (GM Part No. 266316). Figure 3-6 - Steering Linkage NOTE: On vehicles left in long-term storage, the piston rod may become quite rusted. The rod must be cleaned before the vehicle is moved. Failure to clean the rod will destroy the seals with the first inward movement of the rod - making replacement of the damper a certainty. If the damper is not functioning properly, and/or is noisy, refer to a qualified service shop. SECTION 3 STEERI NG, SUSPENSION, WHEELS AND TIRES r GM PART NO. 79-94:22134593 85-92 . P3 with FS3 22046454 ABSORBER ASM-IDLER 3798007 . . . . ., . . RETAINER 6270752 . . . . . . . . GROMMET 9420821 . . . . . . . . 4 9440974 . . . . . . . . RELAY & TIE ROD ASSEMBLY FRAME 9436771 . . . . . . . . NUT 6 357545 . . . . . . . . . a TORQUE TO 45 FT. LBS . MAXIMUM TORQUE OF 60 FT. LBS. PERMISSIBLE TO ALIGN COTTER PIN SLOT (1/16 TURN MAXIMUM) . DO NOT BACK OFF NUT FOR COTTER PIN INSERTION . NUT COTTER PIN ARM ASSEMBLY STEERING IDLER & SHOCK ABSORBER FRONT CROSS MEMBER O NOTE: TORQUE TO 90 IN. LBS. OBTAIN TORQUE BY RUNNING FIRST NUT TO UNTHREADED PORTION OF SHOCK END . TORQUE JAM NUT AFTER TORQUING FIRST NUT . Figure 3-7 - Steering Damper POWER STEERING SYSTEM GENERAL DESCRIPTION The optional power-assist steering utilizes the steering column and linkage previously described . However, the steering gear is different. It combines hydraulic pressure with the mechanical force of a manual steering system to reduce the steering effort required. In addition to a redesigned steering gear, the system requires a pump with pressure and return hoses connecting it to the steering gear. The pump, driven by a belt from the crankshaft, circulates the hydraulic fluid through the steering gear. Valves in the steering gear which are controlled by the steering wheel direct the flow of fluid as appropriate for right or left vehicle turns. The steering gear is of the recirculating ball type. This gear provides for ease of handling by transmitting forces from the wormshaft to the pitman shaft through the use of ball bearings in the same way as the manual steering gear. MAINTENANCE AND INSPECTION Complaints of faulty steering are frequently the result of problems other than the steering gear or pump. Those areas of the steering system which can be easily checked and quickly corrected without disassembly and overhaul of any major components should be attempted first . Conditions such as hard or loose steering, road shock or vibrations are not always due to the steering gear or pump, but are often related instead to such factors as low tire pressure and front-end alignment . These factors should be checked and corrected before any adjustment or disassembly of the power steering gear or pump is attempted . Many factors affect power operation of the steering system of which the most common are : 1 . Fluid level and condition . 2. Drive belt tension . 3. Loose component mountings. 4. Loose pump pulley . 5. Excess front axle weight . These factors must be checked and corrected before making any further diagnosis of the steering system. After the source of the problem has been found, determine the cause . For example, if the oil level in the reservoir is found to be low, refill and check the entire hydraulic system for oil leaks . Refilling the reservoir will not necessarily correct the problem. SECTION 3 - STEERING, SUSPENSION, WHEELS AND TIRES HARD STEERING AT ENGINE IDLE The P-Series motor home power steering assist system is designed for good response up to the 5,000-Ib. suspension capacity. Complaints of little or no steering assist while at idle or with the driver's foot applying the brake are usually the result of the suspension being at or very near capacity . The reason this occurs is that the HydroBoost system has taken some power away from the steering assist system . At this point, the power steering assist system is at borderline capacity. This situation can be corrected by removing the pressure on the brake. This will return the necessary pressure to the steering assist system allowing proper power steering assistance. Also, if additional weight were added to the front axle there would be a momentary system stall requiring slight movement of the vehicle in order to "feel" the power steering assist system operating . GM cannot endorse overloading . To avoid problems concerning overloading, move some load rearward to remove some of the weight from the front axle. Axle weight should never exceed tire or axle capacity. Refer to the proper shop manual for the power steering pump pressure checking procedures. chassis effective on V.I.N. N3310596 . Th e new 710 gear ratio is 17.5:1 and the older 708 gear was 14:1 . The new 710 gear cannot be installed on the older units due to numerous changes and supports . LEAKAGE CHECK If you suspect leakage in the power steering system, follow the guidelines listed below. In some cases you will be able to locate the leak easily, but seepage leaks may be more difficult . 1 . With the vehicle's engine off, wipe the complete power steering system dry (gear, pump, hoses, and connections) . 2. Check oil level in pump's reservoir and adjust as required. NOTE : Typical P-Series - Commercial power steering pump pressure is 1,200-1,300 PSI. Typical P-Series - Motor home power steering pump pressure is 1,350-1,450 PSI. 3. Start engine and turn steering wheel from stop to stop several times. Do not hold in corner for any length of time as this can damage the power steering pump. It is easier if someone else operates the steering wheel while you search for the seepage . In order to improve static steer effort on the P30 (motor home chassis, the steering gear has been changed on all 14,500) - 14,800-16,000 GVW 4. Find the exact area of leakage . Potential leak points are shown in Figure 3-8 . Figure 3-8 - Power Steering Pump Gear Box Leak Points Some leaks can be corrected easily . (See Quick Fixes) . Refer the problem of more extensive leaks to a qualified serviceman for repair . SECTION 3 - STEERING, SUSPENSION, WHEELS AND TIRES QUICK FIXES The purpose of this section is to acquaint you with the types of leakage that can be repaired very easily . It contains information on reservoir oil level, the hoses and the hose connections . An overfilled pump reservoir can be a cause for leakage complaint . The oil in the steering system expands as heated during normal usage . If overfilled, the excess is forced through the breather cap hole and may be sprayed over the engine by air blast. Operate the engine and steering system until normal operating temperature is obtained . Remove the reservoir cap and check the graduated level on the dipstick. Adjust the oil level as required . Seepage at the hose connections can be a cause for leakage complaint and can be due to loose connection nuts. If leakage is observed at the hose connections, and the nut is not cross threaded, tighten the nuts at the gear to 30 ft. lbs . of torque . The nut at the power steering pump should be tightened to 40 ft. lbs. of torque . If tightening to this torque does not stop the leak, refer to the appropriate shop manual . If either the return hose or pressure hose leaks, replace the hose. After the source of a leak has been found and corrected, refill the system with GM Power Steering Fluid (GM Part No. 1050017 - quart size) or equivalent. Avoid the use of automatic transmission fluid in the power steering system since it does not contain the additives necessary for good seal life. In an emergency situation, automatic transmission fluid can be used to "get home." However, it should be replaced with power steering fluid as. soon as is practical . NOTE: Noise in the power steering system on the 14,500 and 14,800 Ib GVW chassis may be the result of air in the system . Air in some cases may be trapped at the high point in the steering line from the reservoir to the steering pump. The air being trapped in this line is the result of line routing in relationship to the pump reservoir . Correct this condition by raising the reservoir 4 inches upward from the present location on the dash and toe panel - see Figure 3-9 . This will route the hoses above the steering pump and eliminate the high point where air is being trapped . The above was a production change in November 1992 beginning with V.I.N. 306209 . NOTE: See page 6 Bulletin 90-391-5 Automatic Park System . CAUTION : Automatic transmission fluid should never be used in the power steering system if the unit is equipped with option F44 -Automatic Park Brake System on the 16000#chassis . NOTE: Contamination in the power steering system (metal flakes) can be removed by installing an A/C filter #25010169 AC-PF 883 in the power steering return line. The filter element should be checked to insure filter doesn't restrict the flow of returning fluid . Component Replacement Lip seals, which seal rotating shafts, require special treatment. This type of seal is used on the steering gear at the .pitman shaft, at the stud shaft, and on the drive shaft of the pump. When leakage occurs in one of these areas, refer the problem to a qualified serviceman for repair. PUMP BELT TENSION ADJUSTMENT 1 . Loosen pivot bolt and pump brace adjusting nuts as required . NOTE: Do not move pump by prying against reservoir or by pulling on filler neck, or damage to the pump could occur. 2. Move pump, with belt in place until belt is tensioned to the specifications . (See Appendix A - Drive Belts and Tension Specifications at the back of this manual .) 3. Tighten the pump brace adjusting nut . Then tighten the pivot bolt nuts. 4. Recheck the pump belt tension . Adjust as necessary. Figure 3-9 - Power Steering Reservoir 3-7 SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES SUSPENSION SYSTEM MAINTENANCE AND INSPECTION The function of the suspension system is to support the vehicle body and chassis over the tires and wheels, and to absorb and cushion road shock. The springs in the suspension cushion the ride while the shock absorbers dampen or control the excess motion (up-and-down bounce) caused by variations in the road surface . The designs of the front and rear suspensions are different, but their function is the same. The front suspension must be lubricated periodically in accordance with the Maintenance Schedule . Grease fittings are indicated in the Lubrication section of this manual . When the suspension is being lubricated, the components should also be checked for obvious signs of damage or wear. Leakage from the shock absorbers may indicate a need for replacement . FRONT SUSPENSION GENERAL DESCRIPTION WHEEL BEARING LUBRICATION The G- and P-Series vehicles incorporate an independent coil spring front suspension system, as shown in Figure 3-10. The control arms are of unequal length (S.L.A. Type) . As a part of normal service, the front wheel bearings should be removed, cleaned, inspected and lubricated each 12,000 miles . Repack the wheel bearings with hightemperature melting grease - approximately 500°F (GM Part No. 1051344 or equivalent) . Refer to the appropriate Chevrolet Light-Duty Truck Shop Manual for the procedure . This suspension system consists of upper and lower control arms pivoting on steel threaded or rubber bushings on upper and lower control arm shafts . The lower control arms are attached to the cross member. The upper control arms are attached to a frame bracket . These control arms are connected to the steering knuckle through pivoting ball joints. WHEEL BEARING ADJUSTMENT CHECK A coil spring is located between the lower control arm and a formed seat in the suspension cross member, thus the lower control arm is the load-carrying member. Doubleacting shock absorbers are also attached to the lower control arms and connect with the frame to the rear on the upper end . The front wheel bearings are tapered roller type and are used on all models . Some P-Series motor homes may be equipped with air bag cylinders to increase the load-carrying capacity of the front suspension . These cylinders are positioned in the center of the coil springs . FRONT SUSPENSION UNIT LOWER CONTROL ARMS NOTE: Tapered roller bearings are used on all series vehicles and they have a slightly loose feel when properly adjusted. A design feature of front-wheel tapered roller bearings is that they must NEVER be preloaded . Damage can result by the steady thrust on roller ends which comes from preloading . 1 . Raise the vehicle and support it at the front lower control arm . 2 . Spin the wheel to check for any unusual noise or roughness. 3. If the bearings are noisy, tight, or excessively loose, they should be removed, cleaned, inspected and lubricated prior to adjustment. If it is necessary to inspect bearings, refer to the appropriate Chevrolet Light-Duty Truck Shop Manual . To check for tight or loose bearings, grip the tire at the top and bottom and move the wheel assembly in and out on the spindle . Measure movement of hub assembly, if movement is less than .001 inch or greater than .005 inch, adjust bearings per the following adjustment procedure . WHEEL BEARING ADJUSTMENT 1 . Remove the hub cap or wheel disc from the wheel . CONTROL ARM SHAFTS 2. Remove the dust cap from the hub . Figure 3-10 - Independent Front Suspension Typical 3. Remove the cotter pin from the spindle and spindle nut . 3-8 SECTION 3 - STEERING, SUSPENSION, WHEELS AND TIRES 4. Tighten the spindle nut to 12 ft. lbs . while turning the wheel assembly forward by hand to fully seat the bearings. This will remove any grease which could cause excessive wheel bearing play later. Refer to Figure 3-11 . 11 . Lower the vehicle to the ground . 5. Back off the nut to the "just loose" position. The air bag cylinders should be inspected periodically for signs of deterioration or damage. Air bag leaks can easily be checked on the vehicle . Inflate with a small amount of air conditioning freon No . 12 then locate the leak using an air conditioning leak detector. To check for possible leaks with the air bag removed from the vehicle, submerge the air bag in water and check for bubbles . (Replace with GM Part No. 367762.) Inflation pressures should be maintained at 10 PSI minimum to avoid chafing . Under load, 40-50 PSI is recommended for a 4,300-Ib . suspension, 50 PSI for a 5,000-lb . suspension . 70 PSI is required on the 5,300-Ib suspension . 80-90 PSI is recommended for the F44 5,500-Ib . optional 16,000-Ib . suspension. This unit uses an Airlift HD bag Part No. 15631881 . Vendor #40-571 6. Hand tighten the spindle nut. Loosen the spindle nut until either hole in the spindle lines up with a slot in the nut, (not more than 1/2 flat) . 7. Install the new cotter pin. Bend the ends of the cotter pin against the nut . Cut off the extra length to ensure that the ends will not interfere with the dust cap. 8. Measure the looseness in the hub assembly . There will be from .001 to .005 inch end play when properly adjusted . 9. Install the dust cap on the hub . 12. Perform the same operation for each front wheel. AIR BAG CYLINDER INSPECTION NOTE: Air bags are currently used on nearly all motor homes and are proposed for use on some GSeries (cut-away) models for 1988-89 . 10. Replace the wheel cover or hub cap . SERVICE TIP - (For units that appear somewhat low in front due to operating at near front suspension capacity.) 3. BACK OFF NUT UNTIL JUST LOOSE POSITION . 2 . TIGHTEN' THE NUT TO 12 FT. LBS . FULLY SEAT BEARINGS - THIS OVERCOMES ANY BURRS ON THREADS ./ 1 . Jack up the motor home by the middle of the front cross member and allow the wheels to hang . 2. Remove the air from the air bag and reinflate the air bag to the proper pressure . 3. Lower the unit and bleed off air (as necessary) to maintain proper air bag pressure . This may provide some ride height improvement as the air bag tends to stretch lengthwise slightly with this procedure . VEHICLE RIDE HEIGHT - FRONT COIL SPRING/AIR BAG REPLACEMENT 5 . LOOSEN NUT UNTIL EITHER HOLE IN THE SPINDLE LINES UP WITH A SLOT IN THE NUT - THEN INSERT COTTER PIN . NOTE : BEND ENDS OF COTTER PIN AGAINST NUT. CUT OFF EXTRA LENGTH TO PREVENT INTERFERENCE WITH DUST CAP 6 . WHEN THE BEARING IS PROPERLY ADJUSTED THERE WILL BE FROM .001- .005 INCH END-PLAY (LOOSENESS) . Figure 3-11 - Wheel Bearing Adjustment The motor home owner should be cautioned in the use of some after-market front coil springs currently available . Some after-market front coil springs are merchandised as a method to increase ride height for the motor home. To obtain this additional ride height, manufacturers have increased the diameter of the wire slightly and added one extra coil. However, use of these after-market springs should be considered very risky for the motor home owner. GM recommends the use of only factory-approved replacement parts for this "safety-sensitive" area of the vehicle. Some after-market coils are physically too large for the normally designed working area of the front coil spring as the wheel goes through its ride travel. On crush, these after-market springs can create a metal-to-metal "coilbound" condition before the ride stops come into play. (The damage created by using a metal-to- metal solid coil can be compared to installing a piece of well casing in 3-9 SECTION 3 STEERING, SUSPENSIO N, WHEELS AND TIRES place of a spring, then raising the vehicle in the air and dropping the vehicle to the ground.) The force of this metal-to-metal "coil-bound" condition is transferred directly into the potential destruction of the lower ball joints or broken lower control arms. The addition of a spring shim (donut-type spacer) has a similar effect of promoting a "coil-bound" condition . Complaints of air bag failures are also the result of these after-market front coil springs . The springs have a tendency to "pinch" the air bag between the coils on crush. Front coil springs should ONLY be replaced by a qualified service shop. Access to the front coil spring and the air bag is gained by lowering the lower control arm . CAUTION : USE ONLY GM APPROVED REPLACEMENT PARTS FOR THIS SAFETY-SENSITIVE AREA OF THE VEHICLE . 1984 to Current . . . . . . . . . . . . . . . . . . GM Part No. 14054345 Prior to 1984 . . . . . . . . . . . . . . . . . . . . . . . . GM Part No. 472222 NOTE : 1984 to current front springs (GM Part No . 14054345) can be used for 1983 and prior years that require front spring GM Part No. 472222 . This will raise the front of the vehicle 3/8 inch to 1/2 inch measured at the "A/BC" measurement location shown in Figure A3-2-1 . Study Figure A3-2-1 at the back of this section of the manual to determine if the useful life of the front coil springs is exhausted and replacement of the front coil springs is necessary. SHOCK ABSORBER DIAGNOSIS (Follow the Procedures Outlined Below in the Order Indicated .) Inspection and Ride Test : The importance of a near equal Rear Axle-to-Frame/Sideto-Side Measurement cannot be overstressed . This near equal measurement has a direct effect on desirable vehicle handling and on the front-end alignment "A or BC" dimension (with independent suspension) . Generally, a near equal "D" dimension (see Figure 3-12) at the rear axle is needed in order to obtain an acceptable front-end alignment . However, the motor home owner should be cautioned in the use of certain after-market suspension devices . These devices are merchandised as leveling devices to raise the "sagging" rear of the vehicle which may be caused by an overload situation or a weight distribution problem . Some of these after-market leveling devices severely limit the wheel travel that was designed into the GM chassis . The following case study is presented as an aid to the motor home owner in identifying potentially dangerous aftermarket vehicle leveling devices . GM CASE STUDY: A motor home was loaded to a maximum GVW, both front and rear. Sufficient air was applied to a typical after-market leveling device to establish a "dead-level" frame. In this case study, wheel travel was limited to 3/4 inch before the after-market device "went solid metal-to-metal" between the rear axle and the frame. This severe limitation on wheel travel promoted a "crashthrough situation" on even the slightest bump. The force from this "crash-through situation" was transmitted into the vehicle frame, rear axle and the coach itself . GM has determined that these types of after-market leveling devices can be very damaging to the motor home and also can affect vehicle handling and are therefore potentially very dangerous . If vehicle weights cannot be shifted due to vehicle build, consideration should be given to adding spring leaves or spacer blocks . TIRE PRESSURE-Check the tire pressure and compare it to the recommended specification on the GVW label in the motor home . Adjust the pressure to specification as required. Poor vehicle control and ride complaint are caused in many cases by improper tire inflation . SPECIAL SUSPENSION EQUIPMENT - Check the Service Parts Identification Sticker for any special suspension equipment, such as a heavy-duty suspension. Vehicles equipped with this type of option have a somewhat stiffer or harsh ride, and this should be kept in mind. Stiffness may occur while vehicle is still new (under 5,000 miles) . The ride should improve somewhat after 7,000 to 8,000 miles . VEHICLE LOAD CONDITIONS - Unusual load conditions can affect the ride and handling of the vehicle . If unusual loading is apparent, check the distribution of this weight . Note if it is all toward one side of the vehicle or at the extreme rear of the vehicle . Reposition load as required to obtain a more uniform weight distribution . Fioure 3-12 - Rear Axle-to-Frame/Side-to-Side Measurement SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES If the vehicle is within the rear spring rating but heavier ment. With most motor homes, you can add a spacer block on one side (tending to lean toward the generator or some of approximately 3/4 inch without replacement of the other heavy appliance), you might consider adding a U-bolts. A minimum of 2 full threads on the U-bolt must spacer block of sufficient thickness to equalize the left/ extend thru the nut . right axle-to-frame measurement . Spacer blocks are not sold as GM parts but are fabricated at local machine CAUTION : AS THE BACK OF THE VEHICLE IS shops . Installation of a spacer block and/or spring leaf is RAISED, THE REAR HYDRAULIC FLEXIBLE BRAKE not covered by the GM warranty. The following information HOSE (RUNNING FROM FRAME MIDPOINT TO THE is provided as an aid to the motor home owner for loading AXLE) IS EFFECTIVELY SHORTENED . DAMAGE CAN situations. RESULT TO THE REAR HOSE WHEN THE AXLE DROPS AWAY FROM THE VEHICLE TO THE LOWER NOTE : The addition of a spacer block can actually im- END OF THE WHEEL TRAVEL (WHEN THE VEHICLE prove overall ride quality while the addition of a ENCOUNTERS A CHUCK HOLE) . CHECK TO MAKE spring leaf tends to reduce the ride quality of the SURE THAT THE REAR HOSE IS LONG ENOUGH TO vehicle . AVOID DAMAGE IN SUCH A SITUATION . IF THERE IS ANY DOUBT, REPLACE THE REAR HOSE WITH A Spacer blocks can be added to either side or both sides LONGER HOSE AND THEN BLEED THE BRAKES . of the vehicle and of different thickness to equalize or DRIVE LINE ANGLE MAY ALSO BE AFFECTED . "open up" the "D" dimension shown in Figure 3-12 . Spacer blocks are generally 21 /2 inches wide by 6 inches long and are installed between the spring pack and spring seat. (See Figure 3-13.) The thickness of the spacer block (to equalize left/right side dimensions) is determined by measuring the "D" dimension on each side and then subtracting one side's dimension from the other. The result is the thickness of the spacer block required for the low side of the vehicle . Raising the back of the vehicle is generally trial and error . This is accomplished by driving the vehicle over stacked pieces of plywood 1/2 inch to 1 inch thick (in a level area) and checking that the side trim of the vehicle is level with each height increase . When the side trim is level and eye appealing to the owner, measure the height of the pieces of wood and add spacer blocks to equal that measure- The spacer block has a 3/4-inch hole drilled in the center. A slip-fit dowel, as long as the thickness of the spacer block, is inserted into the hole of the block. The center bolt head of the spring pushes the dowel down into the pocket in the spring seat and extends into the axle housing seat hole, as shown in Figure 3-14. 3/4" HOLE AND SLIP-FIT DOWEL DOWEL EXTENDED INTO AXLE HOUSING SEAT HOLE Figure 3-14 - Spacer Block Positioning NOTE: There are several different spring center bolt head sizes available . The P-Series motor home chassis requires a 3/4-inch spring center bolt head size. SPACER BLOCK EQUALS THE LENGTH AND WIDTH OF SPRING SEAT ON AXLE HOUSING Figure 3-13 - Spacer Block VEHICLE RIDE AND HANDLING CHECK - After completing the previous checks, drive the vehicle to determine if the problem has been corrected or to definitely establish the type of problem that still exists. If the problem still exists (poor handling, bottoming, noise, ride sway, etc .), the shock absorbers may be the cause . Refer to the appropriate Chevrolet Light-Duty Truck Shop Manual for more extensive test procedures. 3-1 1 SECTION 3 STEERING, SUSPENSION, WHEELS AN D TIRES REAR SUSPENSION GENERAL DESCRIPTION Both the G- and P-Series vehicles use a leaf spring/solid rear axle suspension system . NOTE: 1993 SOP the 14,500-14,800-16,000# units are equipped with the new taper leaf spring . The rear axle assembly is attached to multi-leaf springs by U-bolts . The spring front eyes are attached to the frame at the front hangers, through rubber bushings. The rear ends of the springs are attached to the frame by the use of shackles which allow the spring to "change its length" while the vehicle is in motion . Control arms are not required with leaf springs . (See Figure 3-15.) Ride control is provided by two identical direct doubleacting shock absorbers angle-mounted between the frame and brackets attached to the axle tubes . On G-Series vehicles, the shock absorbers are mounted to the front of the axle on the right side, and to the rear of the axle on the left side. For P-Series vehicles, both right and left shock absorbers are mounted to the front of the axle. MAINTENANCE AND INSPECTION Since the rear springs and shock absorbers use rubber bushings in the mounts, no lubrication is required . However, inspect the suspension periodically for worn or damaged components such as weak or broken spring leaves, leaking shock absorbers, and loose or broken mounting bolts, etc . Check for uniformity of ride height between right and left sides . Replace any worn or damaged parts . Figure 3-15 - Rear Spring Installation G-Series -- Typical The U-bolts attaching the rear axle to the leaf springs should be checked and retightened to the specified torque after the first 500 miles of vehicle operation . Recheck the U-bolt torque each 10,000 miles thereafter . Torque specifications are listed in the chart which follows : U-BOLT TORQUES- REAR Model Bolt Diameter G-10,20 G/P-20,30 P-30 Rear shock absorbers should be inspected and their operation checked following the same procedures for shock absorbers listed in this section under Front Suspension . . 9/16 in. 5/8 in. 3/4 in. Torque 115-130 ft. lbs . 125-175 ft. lbs. 200 ft. lbs . Rear shock frame brackets can be purchased separately if damaged or broken . Item No. 2. 1985-92 1988-92 19 3-1 2 178" W13 208" WB L.H. No. 15638125 R.H. No. 15638126 SECTION 3-STEERING, SUSPENSION, WHEELS AND TIRES WHEELS AND TIRES Use the proper size torque wrench when installing wheels . Hand tightening without a torque wrench or the use of a power impact tool can result in installation torques which are too high or too low. It will help prevent loosening, of the wheel stud nuts and excessive stress placed on the stud bolts . GENERAL DESCRIPTION The factory-installed tires and wheels are designed to operate satisfactorily with loads up to and including the full rated load capacity when inflated to the recommended inflation pressures . INFLATION PRESSURE The maximum cold inflation pressures for the factoryinstalled tires are listed on the Certification Label. (See Figure 3-16.) Tires must be inflated to these pressures when the Gross Vehicle Weight Rating (GVWR) or a Gross Axle Weight Rating (GAWK) is reached . For partial or uneven load distributions (front to rear), proper tire inflation pressure can be determined from the procedure under Determining Wheel/Tire Loads in this section . Improper tire inflation pressures for the load the vehicle is carrying can adversely affect tire life and vehicle performance. Correct tire pressures and driving techniques have an important influence on tire life . Heavy cornering, excessively rapid acceleration, and unnecessarily sharp braking increase tire wear. MAINTENANCE AND INSPECTION TIRE INSPECTION AND ROTATION Front and rear tires-perform different jobs and can wear differently depending on the type of roads driven, individual driving habits, etc . To obtain maximum tire life, tires should be inspected at intervals shown in the Maintenance Schedule . For the longest tire life, anytime irregular wear is noticed, the tires should be inspected and rotated and the cause of the uneven wear corrected . Be certain to check wheel nut tightness (using a torque wrench) and to adjust the tire pressures, front and rear, after rotation to agree with the recommended pressures . Recheck the torque (Figure 3-18) at 100 and 1,000 miles of operation after wheel installation, then, once every 6,000 miles thereafter . ' Figure 3-16 -Certification Label For improved ride comfort in vehicles rated at 8,600 lbs. GVWR, it is permissible to use the lower tire pressure values shown on the label located on the rear edge of the driver's door provided there is a maximum of 200 lbs . cargo, no slide-in camper, and there are three or fewer occupants . The lower GVWR and GAWR (rear) reflect the maximum load-carrying capacity of the tires at lower pressure . Too low an air pressure can result in tire overloading, abnormal tire wear, adverse vehicle handling, and reThe outer tire on a dual wheel will skid or drag on a turn. duced fuel economy . The tire flexes more and can build because of the difference in the turning radii of the inner up excessive heat, weakening the tire and increasing susand outer tires . This results in faster wear of the outer tire. ceptibility to damage or failure . Too high an air pressure In general, the tire with the largest diameter or least wear can result in abnormal wear, harsh vehicle ride, and inshould be positioned at the outside of each dual wheel. creased susceptibility to damage from road hazards. In addition, when vehicles are operated continuously on Lower inflation pressures should be used only with rehigh-crown roads an increase in air pressure of from 5 to duced vehicle loads and the rear tire pressure should be 10 PSI in the outside tire of each dual produces maximum equal to or greater than the front pressure on single wheel application . After determining the load on each tire by tire life. weighing the vehicle on a scale, the correct cold inflation The "X Method" of rotation is recommended with ra- pressures for the actual tire loads can be obtained from dial tires. Due to their design, radial tires tend to wear the Tire/Wheel Load and Inflation Pressure Charts shown faster in the shoulder area particularly in the front posi- in Figure 3-17. Refer to the owner's and driver's manual for additional information on inflation pressure. tions . This makes regular rotation especially necessary . With dual wheel installations, it is recommended that the circumference of each tire to be installed on the rear axle be measured with a steel tape. If all tires do not measure the same, the two larger tires should be installed on one side and the two smaller tires on the opposite side. DETERMINING WHEEL/TIRE LOADS To determine the load carried by each wheel and tire, weigh the motor home in two stages . First, position the vehicle with the front wheels on the scale, and take a 3- 1 3 SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES weight reading . Divide this reading by two to determine the load carried by each tire/wheel . Next, position the vehicle with the rear wheels on the scale, and take the second weight reading . Divide this reading by two (single rear wheels) or four (dual rear wheels) to determine the tire/wheel loads . Then, inflate tires to the proper pressure as determined by load. (See Figure 3-17.) WHEEL AND TIRE BALANCING It is desirable from the standpoints of tire wear, vehicle ride and handling ease to maintain proper balance of wheel and tire assemblies on all models . This may be accomplished by either of the two types of balancing systems in current use which balance wheels either on the vehicle or off . The "on the vehicle" type, however, is the more desirable in that all rolling components (brake drums, bearings, seals, etc.) are included in the balancing procedure and thereby have any existing unbalance cor- rected . Because of the specialized equipment required, wheel and tire balancing should be performed by a qualified service shop. TIRE REPLACEMENT When replacing tires, be sure to consult your owner's and driver's manual for information regarding the proper tire selection . Use of the incorrect size or type of tire may affect load-carrying capacity, ride, handling, speedometer/odometer calibration, vehicle ground clearance, and tire clearance to the body and chassis . If replacing only a single tire, it should be paired on the same axle with the least worn tire of the others. CAUTION : DO NOT MIX DIFFERENT TYPES OF TIRES ON THE SAME VEHICLE SUCH AS RADIAL, BIAS, AND BIAS-BELTED TIRES EXCEPT IN EMERGENCIES, BECAUSE VEHICLE HANDLING MAY BE SERIOUSLY AFFECTED AND MAY RESULT IN LOSS OF-CONTROL. G-SERIES (TIRE AND WHEEL LOAD LIMITS ARE SHOWN BELOW. VEHICLE LOADING MUST BE LIMITED SUCH THAT NEITHER THE WHEEL LOAD LIMITS NOR TIRE INFLATION ARE EXCEEDED .) TIRE SIZE AND LOAD LIMITS -LBS. TIRE SIZE TIRE REV. PER MILE LOAD ~ RANGE 30 C 734 D 712 D 8.75-16.5 712 E 8.00-16.5 734 8.00-16.5 8.75-16.5 8.00-16.5 8.75R16 .5 734 712 40 70 75 2470 2570 2680 2350 2470 2570 80 BIAS TIRES USED AS SINGLES 734 8.00-16.5 35 INFLATION PRESSURE - PSI 65 45 50 55 60 1360 1490 1610 1730 1360 1490 1610 1730 1840 1945 2045 1570 1720 1850 1990 2110 2240 2350 1570 1720 1850 1990 2110 2240 2350 BIAS TIRES USED AS DUALS C D 1195 1310 1415 1520 1195 1310 1415 1520 1620 1710 1800 RADIAL TIRES USED AS DUALS E 1570 1720 1850 1990 2110 2240 2680 *`NOTE: Wheel code is located on the wheel just to the right of the valve stem hole. G-SERIES WHEEL CODE AND LIMITS MAX. MAX. MAX. MAX. LOAD PRESSURE LBS . PSI CODE WHEEL SIZE , LOAD LBS . PRESSURE PSI CODE WHEEL SIZE BR 15x7 JJ 1690 40 YD 16.5x6 2680 85 CD 15x6.5 JJ 1690 40 YH 16.5x6 2680 85 XH 15x6 JJ 1585 40 YJ 16.5x6.75 2680 85 XW 15x6 JJ 1910 70 NO CODE 15x6 .5 JJ 1690 40 Figure 3-17-Tire/Wheel Load and Inflation Pressure Charts 3-1 4 SECTION 3 - STEERING, SUSPENSION, WHEELS AND TIRES P-SERIES (TIRE AND WHEEL LOAD LIMITS ARE SHOWN BELOW, VEHICLE LOADING MUST BE LIMITED SUCH THAT NEITHER THE WHEEL LOAD LIMITS NOR TIRE INFLATION PRESSURE ARE EXCEEDED .) RADIAL TIRE SIZE AND LOAD LIMITS - LBS . LOAD RANGE F INFLATION PRESSURE - PSI TIRE SIZE TIRE REV. PER MILE LT215/85R16 682 C 1495 1785 1940 LT215/85R16 682 D 1495 1785 1940 LT235/85R16 653 D 1700 2030 2205 LT235/85R16 653 E 1700 2030 2205 35 45 50 60 65 75 80 2905 3042 FRONT METRIC RADIAL TIRES USED AS SINGLES 2180 2335 26 23 2485 2623 REAR METRIC RADIAL TIRES USED AS DUALS LT215/851316 682 C 1360 1625 1765 LT215/85R16 682 D 1360 1625 1765 TIRE SIZE TIRE REV. PER MILE LOAD RANGE 1985 2150 INFLATION PRESSURE - PSI 55 60 65 70 FRONT METRIC RADIAL TIRES USED AS SINGLES (MICHELIN) 8R19 .5 617 D 2355 2517 2682 2800 REAR METRIC RADIAL TIRES USED AS DUALS (MICHELIN) 8R19 .5 617 D 2287 2442 2597 2700 BIAS TIRE SIZE AND LOAD LIMITS - LBS. TIRE SIZE TIRE REV. PER MILE LOAD RANGE INFLATION PRESSURE - PSI 30 35 40 45 50 55 60 65 70 75 FRONT -BIAS TIRES USED AS SINGLES 7 .50-16 652 C 1620 1770 1930 2060 7 .50-16 652 D 1620 1770 1930 2060 2190 2310 2440 7 .50-16 652 E 1620 1770 1930 2060 2190 2310 2440 2560 2670 2780 8-19 .5 613 D 2270 2410 2540 2680 2800 8-19.5 613 E 90 3170 3170 REAR BIAS TIRES USED AS DUALS 7 .50-16 652 C 1430 1565 1690 1815 7 .50-16 652 D 1430 565 1690 1815 7 .50-16 652 E 8-19 .5 613 D 2230 2350 2460 8-19 .5 613 E 2230 2350 2460 1930 2040 2140 2245 2345 2440 2570 2680 WHEEL;CODE AND LIMITS CODE WHEEL SIZE AF or AR 16x6K LOAD LBS. MAX. PRESSURE PSI CODE WHEEL SIZE LOAD LBS . MAX. PRESSURE PSI 2440 80 ZY 19 .5x6 2540 80 ZT 19 .5x6 2780 95 Figure 3-17 - Tire/Wheel Load and Inflation Pressure Charts (Continued) See Owners Manual 3-15 SECTION 3 - STEERING, SUSPENSION, WHEELS AND TIRES RADIAL TIRES USED AS SINGLES TIRE SIZE TIRE REV. PER MILE LOAD RANGE 7.501316 654 D 7.501316 654 D INFLATION PRESSURE - PSI 35 1620 40 1770 45 1930 50 55 60 2060 2190 2310 1690 - 1815 1930 20 4 0 DUAL 1430 1565 SINGLES TIRE REV. PER MILE LOAD RANGE 55 60 65 225/701319.5 646 F 2475 2650 F 2377 2557 2140 2835 70 3040 75 3220 80 3405 85 3640 2755 2862 2970 3185 3415 DUAL 646 I INFLATION PRESSURE - PSI TIRE SIZE 225/701119.5 65 2440 Two wheels are used on the assembly line that turns out the GM P-32 motorhome chassis. Chassis with gross vehicle weight ratings (GVWR) of 10,500 pounds to 12,300 pounds use a 19.5 x 6, 8-hole wheel with a 6.5-inch bolt circle part number 15963341 . Chassis with a GVWR of 14,500 pounds to 16,000 pounds use a 19.5 x 6, 10-hole wheel with a 7.25-inch bolt circle - part number 14005758. SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES CAUTION : USE A TORQUE WRENCH TO TIGHTEN LUG NUTS. TIGHTENING BY HAND OR WITH AN IMPACT WRENCH IS NOT RECOMMENDED . TORQUE SPECIFICATIONS LISTED ARE FOR DRY THREADS WITHOUT LUBRICATION . UNDER CONDITIONS OF ABNORMAL CORROSION, A MODEST AMOUNT OF LUBRICANT ON THE FIRST THREE THREADS OF THE WHEEL STUDS SHOULD ALLEVIATE ANY DIFFICULTIES. DO NOT USE PENETRATING OIL . DO NOT APPLY LUBRICANT TO THE BALL SEATS OF THE WHEELS OR TO THE BALL FACES OF CAP NUTS. SERIES DESCRIPTION Stripped threads on the stud bolts may be the result of excessive torquing of the studs (Figure 3-19) or may be the result of damage during wheel installation (when placing the wheel over the studs) . TORQUE (FT. LBS.) G20 1/2 In . Bolts (5) G-30, P-20, 30 Single Wheels 9/16 In . Bolts (8) 90-120 9/16 In . Bolts (8) 140 Heavy Duty 5/8 In. Bolts (10) 180 G-, P-30 Dual Wheels TYPICAL WHEEL AND STUD BOLT FAILURES Worn/Broken Stud Bolts 75-100 Figure 3-18 - Wheel Nut Tightening Sequence and Torque Specifications WHEEL STUD BOLT REPLACEMENT When one wheel stud bolt is broken on axles using fiveto nine-bolt wheels, all stud bolts should be replaced . When one stud bolt is broken on an axle using ten-bolt wheels, the broken bolt, plus the adjacent bolt on each side should be replaced . The additional stress placed on bolts adjacent to the broken bolt weakens them and is the reason for replacement. Figure 3-19- Stripped/Broken Wheel Stud Bolts Broken studs are a direct result of operating with loose cap nuts or improperly seated wheels. Worn/Cracked Wheels Worn wheel stud holes will usually be accompanied by evidence of a bright, worn surface on the wheel face. This condition indicates that loose wheels were working against each other . As shown in Figure 3-20, the stud holes are out of shape and a build-up of metal occurs around them. This condition requires that the wheels be replaced . NOTE : Firestone Steel products are now Accuride Wheels Henderson Kentucky P.O. BOX 40 ZIP 42420-0040 PH 502 826-5000 . SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES Figure 3-20 - Worn/Cracked Wheels Cracks running from stud hole to stud hole (Figure 3-20) on the bolt circle indicate a loose-mounting condition . Cracks running from hand hole to stud hole, hand hole to hand hole, or hand hole to rim are a direct result of overloading . If this type of failure occurs, the position of the failed wheel on the vehicle should be noted and the actual working loads of that axle should be checked . BENT RIM CHECK/TIRE TO RIM MATCHING NOTE: For this measurement, the tire should be "run" recently so that it is warm to avoid a false reading of cord "flattening" which is caused from sitting stationary. 3. Remove the tire from the rim and measure both the radial and the lateral runout at the bead area of the rim as shown in Figure 3-21 . Using chalk, mark the high point on the radial runout of the rim . The following procedure can be used to check for a bent rim or to properly match a tire to a rim . 4. Check the runout specifications listed in Figure 3-21 . If the runout does not exceed the listed specifications, remount the tire on the rim . Position the high point of 1 . Mount the suspect wheel end tire assembly on a suitthe tire (marked with chalk) OPPOSITE (180 degrees) able fixture such as an off-car wheel balancer or front from the chalk mark designating the high point of the spindle of the vehicle . rim . This procedure presents the least amount of radial vibration potential . 2. Using a dial indicator, measure the center point of the tire thread . Mark the high point with chalk (to be used 5. Balance and remount the wheel and tire assembly on in Step 4). the vehicle . HIGH SPOTS a"4 g MAXIMUM WHEEL RUNOUT SPECIFICATIONS RADIAL .030" FA~nn 1 TIRE WHEEL jLOW SPOTS WHEEL TIRE LATERAL .055" MEASURING RADIAL RUNOUT MEASURING LATERAL RUNOUT Figure 3-21- Radial/Lateral Runout Measurement 3- 1 7 SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES EFFECT OF OVERLOADING ON TIRE WEAR Tires that are loaded beyond their maximum-rated carrying capacity will have their useful life significantly shortened. As shown in Figure 3-23, tire life decreases rapidly as overloading increases . For example, it is seen that only a 10 percent overload reduces tire life by about 15 percent . An overload of 50 percent reduces tire life by 60 percent . - 00 90 60 w U LOSS OF SERVICE DUE TO OVERINFLATION 70 w The dotted line is a projection of the solid curve, obtained with actual tire experience over a long period of time. The extreme left end of the solid curve shows that running tires at less than rated load results in a substantial increase in tread mileage . IL 0 z w w a 50 "~ F SERVICE DUE NDERINFLATION 40' " ao MAN E ZO N L -_ _- - 10 0 40 60 60 100 120 140 PERCENT OF RECOMMENDED INFLATION Figure 3-22 - Effect of Inflation on Tire Wear TIRE WEAR Proper inflation pressures for various tire loads are shown in Figure 3-17. For maximum tire life, these pressure recommendations should be followed. Both overinflation and underinflation can greatly reduce tire life. Likewise, the life of overloaded tires is shortened considerably . Greatest tire economy is achieved by selecting tires large enough to carry maximum loads without overloading, and by adjusting inflation pressures dpwnward when less than maximum loads are carried . Figure 3-23 - Effect of Overloading on Tire Wear EFFECT OF INFLATION ON TIRE WEAR Overinflation - This is one of the greatest causes of tire damage. Overinflation does not add strength to a tire, nor does it compensate for overloading . Instead, it weakens the tire and causes more rapid wear (Figure 3-22). Specifically, overinflation causes (1) rapid wear in center of tread, (2) greater susceptibility to impact breaks, (3) weakening of bead, (4) stresses that lead to tread separation, (5) reduced cushioning, leading to increased truck maintenance costs, and (6) reduced traction and skid resistance . Underinflation - This causes tires to flex excessively, causing heat build-up and increased tire wear (Figure 3-22). Underinflation leads to (1) excessive wear on shoulder of tread, (2) irregular tread wear, (3) ply separation, (4) greater susceptibility to bruising, and (5) tread separation . EFFECT OF OVERHEATING ON TIRES When a tire gets extremely hot by operating over a considerable distance in a severely underinflated or flat condition, or with dragging brakes (these are most common causes), the internal frictional heat created may build up to a point where the tire actually bursts into flame . This usually occurs in a dual assembly where one tire is flat and the other tire continues to operate in an overloaded and/or underinflated condition . In such cases, either the completely flat tire or the tire carrying the load could build up a sufficiently high temperature to ignite, as shown in Figure 3-24. Line A of this chart shows time and tire temperature with a tire operated at proper loading and inflation pressure. Line B shows a 20 percent overload and/or underinflation . Note that the tire temperature has moved into the HOT area of the chart . Line C of the chart reflects a 40 percent overload and/or underinflation which has moved into the DANGER area. 3-113 SECTION 3 STEERING, SUSPENSION, WHEELS AND TIRES 40% OVERLOAD w REAR WHEEL DRIVE ALL TIRES OF THE SAME SIZE, TYPE AND LOAD RANGE DANGER DUAL REAR FRONT a w a W H C7 2 LINE NOTE: It is extremely difficult to extinguish a tire fire since the internal temperature causes repeated ignition . A fire extinguisher should be used to control the fire until the tire can be removed from the vehicle . The best protection against a tire fire is to avoid running on flats and to check operating pressures regularly . 20% OVERLOAD LINE B HOT Z Z W I-- RATED NORMAL o LINE 0 a a C 1 2 3 RUNNING TIME IN HOURS 4ca or,~ Figure 3-24 - Effects of Time, Temperature and Pressure on Tire Wear D Z7 REAR TIRES DIFFERENT TO FRONT TIRES BY TYPE, SIZE OR LOAD RANGE DUAL REAR FRONT OO a00 Figure 3-25 3-19 APPENDIX 3-1 STEERING RELAY AND TIE ROD PARTS IDENTIFICATION The following illustration has been extracted from the GM Parts Book. The typical Parts Book illustration shows group numbers of front-end parts . Major parts numbers have been added for reference. (1978 AND PRIOR) GM PART NO. 3956453 GM PART NO. 3956454 1979 TO CURRENT "P(32)" STEERING LINKAGE 1. 2. 3. 4. 5. 6. 7. 6.870 6.242 8.984 6.230 8.917 N.S . 6.232 8. 9. 10. 11 . 12 . 13 . 14. 15 . 16 . 17 . 18 . 19 . 20 . 21 . 22 . 23 . 24 . 25 . 26 . 8.900 6.233 8.938 6.164 8.938 8.917 6.895 8 .916 8.931 6.870 6.859 6.861 6.861 6.508 6.898 8.984 6.898 8.900 8.929 ROD, Strg Relay . . . . . . . . . . . . . . . . SEAL, Tie Rod Soc Ball Stud . . . . . . FITTING, Lug Straight (1/4"-28) . . . . ROD, Inr Tie . . . . . . . . . . . . . . . . . . . NUT (3/8"-16) . . . . . . . . . . . . . . . . . . CLAMP, Adj Tube (Part of #7) . . . . . TUBE UNIT, Tie Rod Adj (Includes Items 5,6,8) . . . . . . . . . . . . BOLT (3/8"-16 x 1 5/8") . . . . . . . . . . ROD, Otr Tie . . . . . . . . . . . . . . . . . . . PIN, Cotter (1/8" x 1 1/4") . . . . . . . . NUT, Strg Link . . . . . . . . . . . . . . . . . . PIN, Cotter (1/8" x 1 1/4") . . . . . . . . NUT (5/8"-18) . . . . . . . . . . . . . . . . . ARM, Strg Relay and Conn Rod . NUJ' (3/4"-16) . . . . . . . . . . . . . . . . . : WASHER (3/4") . . . . . . . . . . . . . . . . . ROD, Strg Conn . . . . . . . . . . . . . . . . ARM, Pitman . . . . . . . . . . . . . . . . . . . WASHER (1 1/2" OD 7/8 ID) . . . . . . NUT (7/8"-14) . . . . . . . . . . . . . . . . . . GEAR, Strg('1) . . . . . . . .. . . . . . . . . . SEAL, Strg Conn Rod BalStud . . . . FITTING, Lug Straight (1/8"-17) . . . . SEAL, Strg Lnkg Piv Shf . . . . . . . . . . BOLT (7/16"-14 x 1 3/4") . . . . . . . . . . WASHER (7/16") . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6270303 328144 14002550 12309226 458201 3983037 14013037 6271489 6259993 5667628 7834511 3865608 3786454 271 N.S . SUPPORT ASM, Strg Relay (See Items 38,39,40,41,42) . . . . . . . . . 28. 8.917 NUT (7/16"-14) . . . . . . . . . . . . . . . . . . . 29. 8.915 NUT (1/2"-20) . . . . . . . . . . . . . . . . . . . 30. 8.938 PIN, Cotter (3/32" x 1") . . . . . . . . . . . 31 . 6.525 COUPLING, W/Flange Kit, Strg Gr . . . 7828871 32 . 6.525 BOLT, Strg Shft Cplg (3/8"-24 x 1 3/16") . . . . . . . . . . . . . . . . 7807271 33 . 6.895 ARM, Strg Idler . . . . . . . . . . . . . . . . . . 14013036 34 . 6.897 WASHER, Strg Idler Shk Abs Grommet . . . . . . . . . . . . . . . . 3798007 35 . 8.915 NUT (3/8"-24) . . . . . . . . . . . . . . . . . . . 36 . 7.244 GROMMET, Spl (1 7/32" OD 7/8" Thk) . . . . . . . . . . . . . 6270752 37 . 6.895 ABSORBER, Strg Relay and Tie Rod Shk . . . . . . . . . . . . . . . . . 22011982 38 . 6 .896 SUPPORT, WBushings Strg Rly & Conn (Includes Item 39) . . . . . . . . . 3941739 39 . 6.896 BUSHING, Strg Rly & Conn Rod Supt Shf (Included in item 38) . . . . . . 266316 40 . 6.896 SHAFT, Strg Rly & Conn Rod Arm Supt . . . . . . . . . . . . . . 3768940 41 . 6.897 NUT, Strg Rly & Conn Rod Arm Supt Plug . . . . . . . . . . 3768947 42. 6.897 PLUG, Strg Rly & Conn Rod Arm Supt . . . . . . . . . . . . . . 3768945 NOTE 1 : For information on serviceable components refer to applicable Assembly illustration . 3-20 APPENDIX 3-2 TYPICAL LOAD HEIGHT CURVES -MOTOR NOME The following Load Height Curves have been extracted from the 1987 Chevrolet Commercial and Truck Chassis Body Builders Book showing Spring Number and Spring Charts for P-Series Motor Home units. As shown on the following charts, known weights compared to actual "A/BC"'` or "D" dimensions can determine if the spring is performing according to its rating . Actual measurements will be ± 1/2-inch on the chart and normally considered within the spring makers production capability . At or near maximum ratings, most GM leaf springs are designed to be in a slight reverse arch. Check with your local Chevrolet Branch Office Truck Department for Spring Charts for other years and models . '` Depending upon reference sources, this dimension is referred to as either an "A" dimension or a "BC" dimension. For the purposes of this manual, both dimensions have been included to aid the motor home owner in the determination of spring ratings . NOTE: This chart is for the typical P-Series Motor Home. Additional model information is available in the Body Builders Book. 6 472222 = 3,750 LBS. SQUEEZE FORCE 14054345 = 4,190 LBS. SQUEEZE FORCE. Fv 5 WITH PLASTIC AIRBAGS (14054345) J uJ Q H 4 uj 0Cn ~W U ZZ O u_ U a "'A/BC :" FRONT SUSPENSION CROSS MEMBER FLANGE 3 T6 SPRING RATING LOWER CONTROL ARM BRACKET MUST BE MEASURED PERPENDICULAR TO CROSS MEMBER FLANGE . MEASUREMENT IS "IRON TO IRON ." RUBBER BUMPER IS 2 D (P30032) DUAL YD8/F66 WITH PLASTIC AIRBAGS 0 1000 2000 w 3000 4000 5000 6000 7000 8000 LOAD SHOWN IS TOTAL AXLE LOAD AT GROUND-FRONT (POUNDS) 9000 Figure A3-2-1- Load Height Curve "A/BC" Dimension - Motor Home NOTE : 1984 to Current - A front spring with GM Part No . 14054345 can be used for 1983 and prior years that require a front spring with GM Part No. 472222 . This will raise the front of the vehicle 3/8 inch to 1/2 inch measured at the "A/BC" measurement location shown in the chart above . 3-21 APPENDIX 3-2 TYPICAL LOAD HEIGHT CURVES -MOTOR NOME (Cont'd) NOTE: This chart is for the typical P-Series Motor Home . Additional model information is available in the Body Builders Book. w 7 7# P30832 YD9 DUALS P30 32 YD9 DUALS (1432 YD9 DUALS P3 5599368) 3100 lbs. each 6200 total 7 leaf 52 by 2.50 by 2.66 thick Q ILL I1 O O H H O m Oa ww D U ~- z LLJ X Q D Q w D 6 9# P30832 G50 DUALS P31132 G50 DUALS P31432 G50 DUALS 5 3750 lbs. each 7500 tota 8 leaf 52 by 2 .50 by 2 .97 1thick 4 D: TOP 3 F AXLE TUBE T OF FRA - `S I I ILL O O 8# P31432Y88 H D. DUALS P31832 Y138 H.D . DUALS (15599376) 5000 lbs. each 10,000 total 10 leaf 56 by 2.50 by 4.04 (hick 2 SPRING RATING 1AA I qN801h, 2000 3000 4000 5000 6000 7000 8000 9000 LOAD SHOWN IS TOTAL AXLE LOAD AT GROUND-REAR (POUNDS) Figure A3- 2-2 - Load Height Curve "D" Dimension - Motor Home 10000 11000 SECTION 4-PROPELLER SHAFTS AND UNIVERSAL JOINTS PROPELLER, SHAFTS AND UNIVERSAL JOINTS GENERAL DESCRIPTION PROPELLER SHAFTS The propeller shaft is a steel tube which is used to transmit power from the transmission output shaft to the differential . To accommodate various model, wheelbase and transmission combinations, drive shafts differ in length, diameter and the type of splined yoke. Each shaft is installed in the same manner . A universal joint and splined slip yoke are located at the transmission rear extension . The slip yoke permits fore and aft movement of the drive shaft as the differential assembly moves up and down. The spline is lubricated internally by transmission lubricant or grease. An oil seal at the transmission prevents leakage and protects the slip yoke from dust, dirt and other harmful materials . (See Figure 4-1 .) the center bearing, which is mounted in a bracket attached to a frame cross member. The center bearing is permanently lubricated and sealed . UNIVERSAL JOINTS The simple universal joint is basically two Y-shaped yokes connected by a cross member called a spider. The spider is shaped like an "X", and arms that extend from it are called trunnions . (See Figure 4-2 .) The spider allows the two yoke shafts to operate at an angle to each other. Since the drive shaft is a balanced unit, it should be kept completely free of undercoating and other foreign material which would upset shaft balance . Both one-piece, two-piece and three-piece propeller shafts are used depending on the model . On models that use a two-piece shaft, a three-piece or more shaft, the shaft is supported near its splined end in a rubber-cushioned ball bearing, commonly referred to as NOTE: Single exhaust requires only 1 shield . Figure 4-2- Universal Joint-Exploded View DIFFERENTIAL UNIVERSAL JOINTS UNIVERSAL JOINT TRANSMISSION BEARING SUPPORT (CENTER) Figure 4-1 -Propeller Shaft BEARING HEAT SHIELD 15680325 1985-1994 SECTION 4 PROPELLER SHAFTS AND UNIVERSAL JOINTS MAINTENANCE AND INSPECTION Generally, the propeller shaft and universal joints require little maintenance. Periodic inspection is recommended, however, for proper propeller shaft balance and universal joint lubrication . If area around caps appears to be excessively dry, it may indicate a need for bearing relubrication or universal joint replacement. (See Figure 4-2 .) A failing universal joint often squeaks on start-up or "klunks" with direction change. If the center bearing is replaced, the bearing itself does not need to be packed with grease. However, chassis lubricant should be packed within the dust shields to form a dam to aid in preventing water and dirt from reaching the bearing . The dust shields are staked into position following the procedure detailed in the shop manual . (See Figure 4-3 .) Typical U-joint and slip spline failures are shown in Figure 4-4. Figure 4-3 - Center Bearing LACK OF LUBRICATION END GALLING BRINNELLING SLIP SPLINE GALLING Figure 4-4 - Typical Failures - U-Joints and Slip Spline PROPELLER SHAFTS AND UNIVERSAL JOINTS SECTION 4 DRIVELINE NOISE AND/OR VIBRATION CHECKS The following information is presented as an aid to the motor home owner as diagnostic "thought-starters" and are listed as possible causes for driveline noise and/or vibrations. As applicable, references are made to those areas of this manual providing additional information . CHECK IF: " Drivelines are out of static and dynamic balance . See Driveline Balance Procedure section of this manual . " Crosses in the universal joints are worn or damaged . See Figure 4-4 in this section of the manual . DRIVELINE BALANCE PROCEDURE Each piece of a driveline propeller shaft is manufactured to be in "balance" by itself. However, there are times when assembly of two or more shafts together creates an undesirable running combination . The following drive shaft balance procedure can be applied to a motor home and the procedure can be performed on the shop floor. The wheels should be blocked and both axle shafts should be removed to prevent any possibility of spider gear spin-out during the balancing process . The procedure requires the service technician to place four chalk marks (numbers 1 through 4) on the propeller shaft . (See Figure 4-5 and Figure 4-6 .) " Center bearing is worn or loose . See Figure 4-3 in this section of the manual . " Teeth on the ring and pinion gear of the driving axle are worn or pitted . Tires - wheels are out of balance . " Spring U-bolts are loose . " Parking brake drum is warped and/or out of balance . See Figure 6-5 of this manual . Difference in angular velocity of universal joints results from incorrect joint working angles . See Appendix 4-1 and Appendix 4-2 at the end of this section of the manual . " Propeller shaft joints are out of phase on one or more splines . See Appendix 4-1/Figure A4-1-4 or Appendix 4-2/Figure A4-2-6 at the end of this section of the manual . " Propeller shaft does not extend far enough into the slip joint . Propeller shaft should extend into the slip joint 2/3 to 3/4 of the spline length . This should not be less than 2-1/2 inches in length . Figure 4-5 - Chalk Reference Marks on Propeller Shaft ROTATE CLAMP HEADS AWAY FROM EACH OTHER " Weld at the seam of the drive tube running the length of the drive tube is cracked or there is a cracked weld where the U-joint attaches to the propeller tube. " U-joint has a missing needle bearing . This situation usually creates a "snapping" noise under load as the needles straighten under load. See Figure 4-2 in this section of the manual . " Transmission rear support mount worn . Engine block motor mounts worn. Figure 4-6 - Balance Hose Clamps in Position SECTION 4 PROPELLER SHAFTS AND UNIVERSAL JOINTS Run the engine and drive shaft speed up to the point vibration is felt and note the speed showing on the speedometer . Also, note the "intensity" of the vibration . STOP THE ENGINE AND DRIVE SHAFT . Install a hose clamp and position the screw pointing toward one of the chalk reference marks . (See Figures 4-5 and 4-6 .) Retest for vibration and note any gain or loss in vibration disturbance. A single hose clamp will usually increase or reduce the vehicle vibration by feel . The screw portion of the hose clamp is the weight being moved around the shaft . 6. Install two hose clamps on the drive shaft as close to the rear of the drive shaft as possible, as shown in Figure 4-6. Position both screw clamp heads 180 degrees from the heavy point of the shaft as shown by the strobe light . (See Figure 4-8 .) Tighten clamps . NOTE: When the strobe light flashed, the heavy point of the shaft was down at the bottom 6 o'clock position . To balance the drive shaft, it is necessary to position both clamp heads 180 degrees from the heaviest point, or at the top of the shaft in the 12 o'clock position. A wheel balancer with a strobe light helps facilitate the balancing of the propeller shaft . The strobe light shows the amount of weight that is needed and the exact location where the weight is needed . However, human touch on a cross member, pinion nose, or transmission extension housing can be very helpful in combination with the strobe light. 7. Run the vehicle through the speed range of the disturbance. If the problem is eliminated go to Step 9. If the disturbance is not gone and the strobe light shows the clamp heads at the bottom (6 o'clock position) of the shaft, go to Step 8. 1 . Block the wheels and remove both axle shafts . a. If the strobe light shows the two clamp heads at the top of the shaft, add one more hose clamp to the shaft and recheck . If the strobe light still shows the three clamp heads at the top (12 o'clock position) of the shaft, remove the shaft and reinstall it 180 degrees on the rear flange. Recheck the balance without any clamps . If the disturbance is gone, proceed to Step 9. If the disturbance is not gone, repeat the balance procedure beginning with Step 6 . 2. Mark and number the drive shaft at four points 90 degrees apart around each shaft just forward of the balance weights . (See Figure 4-5 .) 3. Place the strobe light wheel balancer pick-up unit directly under the differential pinion nose as far as possible. (See Figure 4-7 .) Repeat this step at each carrier bearing support (for two, three or more drive shaft units) . 4. With the vehicle running in gear at the vehicle speed where the disturbance is at its peak, allow the driveline to stabilize by holding a constant speed . Point the strobe light at the spinning shaft and note the position of one of the numbers on the shaft . b. Generally if more than three hose clamps are needed, the shaft should be replaced unless the hose clamps are positioned opposite the weldedon factory weight . This position of the clamps would indicate that the factory weight position is counter productive in the original position . If the hose clamps are positioned opposite the factory weight, knock off the factory weight and rebalance the shaft beginning with Step 6. CAUTION : NEVER RUN THE, VEHICLE HIGHER THAN 60 MPH. ALL PERSONNEL MUST STAND CLEAR OF THE U-JOINT AND BALANCE WEIGHT AREA AS SERIOUS INJURY MAY RESULT. 5. Shut off the engine. Allow the shaft to stop, then manually turn the shaft until the chalk numbers are in the same position as shown by the strobe light. However, if the clamps are also 180 degrees from their original position after the shaft was rotated 180 degrees, the drive companion flange on the axle is out of balance and must be replaced . 8. Rotate two of the hose clamps equally away from each other toward the top (one each way from the original position as shown in Figure 4-8) in small amounts until you find the best possible balanced condition . In some cases, it may be necessary to use one clamp or possibly as many as three clamps to obtain a proper balance . Figure 4-7 - Strobe Light Wheel Balancer Pick-up Unit NOTE: It may be necessary to repeat these procedures at each cross member carrier bearing with the strobe pick-up contacting the nonmoving metal bearing retainer or against the cross member as close to the bearing as practical. 4-4 SECTION 4 PROPELLER SHAFTS AND UNIVERSAL JOINTS 9. Install the axle shafts and road test the vehicle for final check of balance. NOTE : Vibration felt in the vehicle in the repair stall may not be felt by the driver under road conditions. 10 .;, After final check, drill a 1/8-inch hole through each clamp and drive shaft and install a pop rivet to prevent slip or tampering. STEP 1 STEP 2 STEP 3 DETERMINE POINT OF UNBALANCE ADD HOSE CLAMPS 180° FROM POINT OF UNBALANCE UNTIL THEY BECOME HEAVY SPOT ROTATE TWO CLAMPS EQUALLY AWAY FROM EACH OTHER UNTIL BEST BALANCE IS ACHIEVED Figure 4-8 - Hose Clamp Positions to Balance Shaft NOTE : Many years of engineering and testing are used to develop your motor home chassis for a smooth ride and handling . ' Many units are modified by stretching or shortening of the wheelbase to match the style and/or length of the body by the coach builder. This requires the frame and drive shafts to be cut and some length removed or added which is a long standing practice and does not create any problems if properly reengineered and assembled. However, many times, vibrations are created because the drive shafts and shaft hangers were not properly realigned or rebalanced before delivery . Other times, vibrations and/or damage are caused when different types of rear suspension and/or tag axles (non GM) are installed by either the coach company or later by the owner of the coach. Alterations and/or such modifications noted above which create an owner concern or damage to the coach, are the responsibility of the company or the persons altering the chassis components after final assembly by General Motors . APPENDIX 4-1 DRIVELINE VIBRATIONS-ONE AND TWO DRIVE SHAFT SYSTEMS The following information is directed to service personnel andis presented as an aid to the motor home owner in understanding driveline vibrations (as driveline vibration problems are often not recognized by the owner). Driveline vibrations will generally be a high-speed vibration or a "buzz" at drive shaft speed compared to wheel and tire vibration that is a much slower speed . Standard factory units normally do not have problems unless the assembler in production has installed the incorrect length hanger bearing support or some part is off in design specification . The units most likely to have vibration problems are modified units where a wheelbase is changed, a drive shaft added or a change that has occurred when the suspension has been modified or changed (for example, a spring changed or after-market suspension installed replacing production springs) . Figure A4-1-1 - Driveline Vibration - Case Study Example No. 1 NOTE: The angles shown in Figure A4-1-1 were taken with a very accurate digital protractor and dramatically indicates an ability to work in extremely small figures . In the example (Figure A4-1-1) note that the working angle between the engine and the first shaft of .44 degrees is well within the driveline rules. The first joint does not present any problems. With a .44-degree working angle and no mating joint, a vibration will never be felt. At the back two U- joints, the intent is to make a canceling pair within one-half degree working angle. As shown in the example, this is very poor; 1 .54 degrees minus .18 degrees equals a 1 .36-degree difference - clearly beyond the one-half degree rule. On some units that have operated in a heavy-loaded condition, the last shaft and pinion nose will change enough to require a driveline and/or pinion nose change . The following information should be read by service personnel and understood as a guideline for alignment procedures . NOTE: Motor homes produced with a wheelbase larger than 178 inches will have three drive shafts . However, examine what would happen if a one-degree caster wedge were installed to tip the pinion nose up to more closely follow the rule of setting the pinion to be "equal to the transmission angle or front-shaft angle or an angle between the two ." The following driveline rules are for one and two drive shaft systems . ' Rule Number 1 - The working angles of each pair of Ujoints must be within one-half degree of being equal on shafts that turn at 3,200 RPM or higher, or within one degree of being equal on shafts that turn at speeds below 3,200 RPM. Rule Number 2 - (Involves a two drive shaft, three Ujoint system .) With a three-joint system there is always an odd joint that cannot be'paired with another joint . Since the U-joint between the transmission and the front shaft does not have a mate to cancel out its acceleration and deceleration, the front shaft should be within one-half degree of the transmission angle for high-speed shafts and within one degree for low-speed shafts . If the rear-end pinion angle is not equal to either the engine/transmission angle or front shaft angle, it should be at an angle between those two. There can be one-half degree difference between the center and rear U-joint working angles provided neither of the working angles exceeds 4 degrees on highspeed shafts, or 5 degrees on low-speed shafts . The following is an actual driveline case study of an Struck. The purpose of this example is to indicate that driveline problems are not restricted to large trucks . Figure A4-1-2 - Driveline Vibration - Case Study Example No. 2 The example shows quite an improvement . Note that the two rear joints are canceling within the one-half degree rule. Another point learned in this case study concerns the use of the protractor . A one-degree shim was sent for, which was cast one degree but when installed turned out to be 1 .26 degrees . Another move that would seem to defy one of the driveline rules can sometimes be done on light-duty applications . This involves (through design considerations) keeping the pinion nose as low as possible to help reduce driveline tunnel size and the hump that is needed in the trunk floor for axle clearance . 4-6 APPENDIX 4-1 DRIVELINE VIBRATIONS-ONE AND TWO DRIVE SHAFT SYSTEMS (Cont d), 1 Before completing a discussion of two-shaft drivelines, consider the following : "Could the system be reversed and the one-half degree be placed at the pinion end?" The answer is a technical yes, but in reality, you are better off with the half degree at the engine end . With the solidmount transmission and first shaft, you are generally better off to have your bigger working angles further from the passenger compartment at the pinion end . Noise and vibrations are further away and are somewhat absorbed in springs and suspension . Concerning this, consider what happens to the angles of the middle joint and at the pinion nose as the axle and the drive shaft move through loadings and ride travel . Chances are small of maintaining proper joint relationships . Stay with the one-half degree at the engine, and equal and canceling angles as a pair at the middle joint and pinion joint. Also, remember with a two-shaft system, that the drivelines must be in proper phase at the slip yoke. If off one spline, a vibration complaint will result. The illustrations of Figure A4-1-4 show proper phasing and maximum drive shaft runout. Note the result shown in the case study example (see Figure A4-1- 3) of reversing the shim and tipping the pinion nose down by one plus degree . Figure A4-1-3 - Driveline Vibration - Case Study Example No. 3 As a result, you end up with even smaller working angles but still within the one-half degree cancellation. of Rule Number 1 . This illustrates two very proper approaches to driveline correction (but still returning to the key point of joint working angles canceling in pairs and within one-half degree) . MAKE SURE THE YOKES ON EACH SHAFT ARE PARALLEL MAXIMUM RUNOUT .005" .015" .010" .015" rrn r 3" Using a magnetic base dial indicator, perform a radial runout check of the shaft . Readings at each location shown must be within limits given . I CENTER OF SHAFT hI Figure A4-1-4- Proper Phasing and Maximum Drive Shaft Runout the one common factor among the various combinations - the joint working angles are equal as a pair and qualify under Rule Number 1 . The following examples demonstrate acceptable driveline combinations and are presented as an aid in reemphasizing the simple single drive shaft two-joint system . Note ,-4,0 4-5.0 .0 -IL3.0 +30 `r 3.0 U 0 + 2 .0 +4.0 Figure A4-1-5-Acceptable Driveline Combinations 4-7 +30 -- 0 l, .1-1 _+5.0 APPENDIX 4-2 DRIVELINE VIBRATIONS THREE "SFIAFT DRIVELINES The following information is addressed to service personnel and is presented as an aid to the motor home owner in understanding the three-shaft drivelines typical of RV vehicles and farm trucks . Three-shaft drivelines are perhaps the simplest and mostinteresting of all drivelines because of the many and varied combinations possible. The following are several basic rules : Rule Number 1 - The working angle of each pair of Ujoints must be within one-half degree of being equal on shafts that turn at 3,200 RPM or higher, or within one degree of being equal on shafts that turn at speeds below 3,200 RPM . No working angle shall exceed four degrees on high-speed shafts, or five degrees on low-speed shafts . (This is essentially the same rule as found in single and two drive shaft systems .) Figure A4-2-2 - Driveline Vibrations - Truck Case Study - Example No. 2 The above example shows equal canceling angles . However, the back pair exceed the four-degree maximum working angle of Rule Number 1 . Note the last shaft is negative (uphill to the pinion) . Negative shafts are added to positive shafts . Rule Number 2 - (The concept of the broken back angle .) The first shaft angle plus the third shaft angle is divided by two and equals the second shaft angle. For example : A first shaft of zero degrees plus the third shaft of 90 degrees equals 90 degrees divided by two equals 45 degrees as the proper setting for the second or middle shaft. The following chart shows the relationship of shaft speed to maximum allowable working angle . Rule Number 3 - When computing working angles, two components that are tilted in the same direction are subtracted from each other. When connecting components are not in the same direction, such as a positive and a negative angle, the angles are added to determine the working angle . RPM 5000 4500 4000 3500 Max working angle RPM Max working angle 3°15" 3000 5' 5" 3°40" 2500 7o 0" 4 0 15 " 2000 8 ° 40" 50 0" 1500 11°30" Figure A4-2-3 - Shaft Speed To Maximum Working Angle Figure A4-2-1 - Driveline Vibrations - Truck Case Study - Example No. 1 In the above truck case study, the requirement was to raise the driveline system to eliminate the negative last shaft running uphill to the pinion . This situation created working angles that were too large . In this case study example, the broken back angle becomes an advantage and drastically reduces work in the process . (The original example shown in Figure A4-2-1 had the pinion nose at two and one-half degrees and the center shaft at three degrees.) Examine the truck case study shown in Figure A4-2-1 . To better understand the truck case study, draw a line vertically down through the middle drive shaft . You will find that you are really working with two trucks with single drive shafts . As you apply Rule Number 1, you will notice that there is not a problem with the rear pair of joints, but the front half of the truck, with three degrees of working angle and zero degrees for its mating joint, presents a problem. With single-shaft drivelines, one method to employ would be to align the shafts so the shafts operate in parallel planes, but at different levels. (See Figure A4-2-2 .) For example : Lower the second shaft to six degrees, and by installing a caster wedge, tip the pinion nose up slightly to six degrees . Using Rule Number 2, the following presents a case study example of a broken back angle out of the front of the truck . With the engine as the first shaft, and the middle drive shaft considered as the third shaft, determine the shaft setting for the second shaft . Use two and one-half degrees for the third shaft . 4-8 APPENDIX 4.2 DRIVELINE VIBRATIONS THREE"SNAFT DRIVELINES (Cont1d) 6 2 1/2 8 1/2 degrees as the first shaft degrees as the third shaft degrees divided by two equals 4 1/4 degrees second shaft Figure A4-2-4 - Drivellne Vibrations - Truck Case Study - Example No. 3 The following shows a broken back angle installed in the front half of the truck case study example . Figure A4-2-5 - Driveline Vibrations - Truck Case Study = Example No. 4 Note that by picking the middle shaft to be the same as the pinion, you have corrected the rear of the truck to near ideal cancellation, as well as correcting the front of the truck . Changing hanging bearing length is generally a cutand-weld as an overlap to shorten a hanger, or fabricating a spacer block. (You must locally obtain longer bolts to make a longer hanger.) Almost everything that applies to single-shaft systems applies to three-shaft trucks. Even the broken back angle can occasionally be used in some specialized single-shaft trucks, such as airport luggage toters where the rear axle is moved forward almost under the driver's seat. With a very short drive shaft, parallel alignment would make working angles too large. In the toter, the pinion becomes the third shaft and the engine is the first shaft . The manufacturer may install a broken back to obtain equal working angles at the transmission and the pinion, and reduce working angles in the process . It is also important, as in the two drive shaft truck, to have the last drive shaft properly phased on the slip spline . Make certain the fixed yoke and the splined yoke are in the same plane. If they are off even one spline, a vibration complaint may result. The illustrations below (see Figure A4-2-6) show proper phasing and maximum drive shaft runout . MAKE SURE THE YOKES ON EACH SHAFT ARE PARALLEL MAXIMUM RUNOUT .005" .015" 0.10" Using a magnetic base dial indicator, perform a radial runout check of the shaft. Readings at each location shown must be within limits given . Figure A4-2-6 - Proper Phasing and Maximum Drive Shaft Runout .015" CENTER OF SHAFT SECTION 5 - REAR AXLE GENERAL DESCRIPTION REAR AXLE The rear axle assembly consists of the drive pinion, ring gear, differential and axle shafts in one housing . The drive pinion transfers power input from the propeller shaft to the ring gear which drives the axle shafts and rear wheels . The ring gear is a reduction gear which lowers the speed (RPM) of the propeller shaft to a speed which is usable for driving the rear wheels . MAINTENANCE AND INSPECTION DIFFERENTIAL FLUID The differential requires little maintenance ; however, periodic fluid level checks are recommended to ensure smooth operation . In addition, the fluid should be changed in accordance with the time and mileage intervals listed in the Maintenance Schedule for the vehicle . To check differential fluid level, remove the plug, as shown in Figure 5-1 . If the fluid level is sufficient, fluid will seep out of the opening . If it doesn't, add the necessary amount. Replace the plug, making sure it is properly seated. Figure 5-1 - Rear Axle Lubricant Fill Hole Normal operating temperature of rear axles and manual gear-shifting transmissions is about 1'00 degrees above ambient temperature . Both units are cooled by lube oil. The tube oil carries heat from the friction points to the case where the heat is dissipated into the air flowing past the case. The following are typical examples of overheat possibilities . Overheating can be caused by the : " Housing severely coated with dirt or dried mud which acts as an insulator holding heat in the housing . " Differential operated with low 'lubricant levels due to leaks . " Incorrect or mixed lubricant brands which foam and reduce heat transfer. " Engine exhaust positioned too close to the transmission or a pipe leak directing heat on the differential . " Break-in lubricant not drained quickly enough after being subjected to high break-in temperatures thereby destroying the lubrication additives . " OVERLOADS-Overloads tend to reduce road speeds and cause the vehicle to be operated in lower gears for extended periods of time. This increases heat in the engine, transmission, drive-line universal joints and rear axles . HIGH SPEED OPERATIONS - Very high speeds tend to churn the lubricants to the point that aeration occurs . Lube oil filled with air bubbles cannot carry the heat away from its point of origin to the housings where it can be dissipated into the air stream . " Extended period of time between lube oil changes . The additives contained in lube oils do wear out on a slow and gradual basis . As the additives wear out, the viscosity may change and the lubricating qualities are depleted. Additionally, the metals content (that occurs under normal wear) increases in the gear oil . As this process continues, temperatures and friction increase within the component until a failure occurs . NOTE: Many large fleet operators have the lubricants that are drained from their vehicles analyzed to determine if the change frequency can be in creased or must be decreased . For the individual owner the results of this lubricant analysis may not justify the expense . The individual owner may find that the best method to follow is to drain the fluid every fourth oil change and refill, to check the fluid level and add fluid as needed at every oil change, and in dusty areas or trailer towing applications, to drain the fluid at every oil change and refill . A large loss of fluid in this system may indicate a problem. Have the system inspected and repaired at once to avoid further damage . WHEEL BEARING ADJUSTMENT (TAPERED BEARING) Before checking bearing adjustment, make sure the brakes are fully released and do not drag. NOTE : With any floating axle, wheel bearing lubrication is normally supplied by the gear oil in the axle. Anytime the wheel bearings are replaced or re moved for inspection, it is a good practice to pack the bearings with high temperature wheel bearing grease (GM Part No. 1051344) . The grease packing assures ample initial lubrication . As the rear axle gear oil works its way to the wheel bearings, the grease packing dissolves and is washed away with the gear oil. SECTION 5 - REAR AXLE MODEL SOURCE P30 (With H22/H23) Rockwell TYPE/CAPACITY Dana 70 #10,000 Dana 80 #10,500 Saginaw #10,000 Banjo/11,000# G30 Chevrolet Salisbury/5700# 10-1/2 G30 (Dual Wheel) Dana Salisbury/6200# 9-3/4 G30 (Dual Wheel) Dana Salisburyf7500# 10-1/2 Chevrolet Dana Chevrolet-Saginaw P30 . RING GEAR SIZE (In.) ~ RING GEAR SIZE (In.) 10-1/2 11 .3 10-1/2 12 REAR WHEEL BEARING ADJUSTMENT SPECIFICATION BEARING OUTER RESULTING ADJUSTING ADJUSTING LOCKNUT BEARING NUT TORQUE NUT TORQUE ADJUSTMENT (Ft. Lbs .)* BACK-OFF* (Ft. Lbs .) (In .) 10-1/2 & 11 50 *' 65 9-3/4 50 ** 65 12 90 1/8* 250 **Back off nut and retighten to 35 Ft. Lbs. then, back off 1/4 turn . TYPE OF BEARING .001 TO .010 END PLAY TAPERED ROLLER SLIGHT PRELOADED BARREL ROLLER *With wheel rotating . Figure 5-2 - Wheel Bearing Adjustment Specifications Check bearing play by grasping the tire at the top and pulling back and forth, or by using a pry bar under the tire. If bearings are properly adjusted, movement of the brake drum in relation to the brake flange plate will be barely noticeable and the wheel will turn freely: If movement is excessive, adjust the bearing as follows : 1 . Remove the axle shaft and raise vehicle until the wheel is free to rotate . 2. Keyways and threads on the tube and nut must be clean and free from chips, burrs and shavings. 3. Disengage . tang of the retainer and remove retainer from the axle housing tube. 4. Torque the adjusting nut to 50 ft. lbs., while at the same time rotating the hub assembly and making sure the bearing cones are seated and in contact with the spindle shoulder. r Proper wheel bearing adjustment can be made using a spanner wrench (GM Tool J-2222-L or equivalent) . 5. Back off nut until loose . Refer to Figure 5-2 for specifications . 6. If adjusting nut slot is in alignment with keyway in the axle spindle, insert the square key into slot . If the adjusting nut slot is not aligned, back off nut a slight amount and insert the square key into the slot. Do not back off more than one slot to align the key . 7. Assemble the snap ring at the end of the spindle to retain the key in position . WHEEL BEARING ADJUSTMENT (BARRELTYPE BEARING) Before checking bearing adjustment, make sure brakes are fully released and do not drag . NOTE: With any floating axle, wheel bearing lubrication is normally supplied by the gear oil in the axle. Anytime the wheel bearings are replaced or re moved for inspection, it is a good practice to pack the bearings with high temperature wheel bearing grease (GM Part No. 1051344) . The grease packing assures ample initial lubrication . As the rear axle gear oil works its way to the wheel bearings, the grease packing dissolves and is washed away with the gear oil. Check bearing play by grasping tire at, top and pulling back and forth, or by using a pry bar under tire. If bearings are properly adjusted, (installed with slight preload), there will be no movement of the brake rotor and the wheel will turn freely. If there is movement, adjust bearings by using the following procedure : 5-2 SECTION 5 - REAR AXLE 1 . Remove axle shaft and raise vehicle until wheel is free to rotate . 2. Disengage tang of retainer from locknut and remove both locknut and retainer from axle housing tube, with GM Tool J-25510 or equivalent. Gross Combination Welgid (6CWI In Pounds under 45,000 50 .000 Rattaeed 3. Tighten inner adjusting nut (using GM Tool J-25510 or equivalent) to 90 ft. lbs. torque while rotating wheel hub at the same time to make sure all bearing surfaces are in contact . Then back off inner nut 1/8 turn while rotating wheel. The wheel should turn freely. 4. Install tanged retainer against the inner adjusting nut . Align inner adjusting nut so short tang of retainer will engage nearest slot on inner adjusting nut . 5 . Install outer locknut and tighten to correct specified torque (250 ft. lbs.). Then bend long tang of retainer into slot of outer nut . AXLE HOUSING A gear set operated at its capacity rating will give 100 percent of rated life . Taking the same gear set and reducing the work load will give a very large gain in life. Overloading by even very small percentages causes a very serious loss in life. Overloading also tells a major story on increased tire wear, wheel bearing and axle housing failures. The graph shown in Figure 5-3 (provided by Eaton Axle Division) indicates the approximate percentage of life expectancy of axle gear sets and other axle parts. The figures are based upon dynamometer tests (conducted by Eaton Axle Division) and are the direct result of accurately simulated load conditions. NOTE: A gear set operated at its capacity rating will give 100 percent of rated life . 300% of Normal Life 81 % (of capacity) 160% of Normal Life 90% 55 .000 60 .000 109% 65 .000 118% 100% - Normal L8e 160% of Normal Life 36% of Normal Life 70 .000 127% 24% of Normal Lilt 1 Over 75 .000 136% J 18% of Normal Life Figure 5-3 - Average Life of Overloaded and Underloaded Gears BENT AXLE HOUSING Overloads destroy axle housings and flexed housings tend to excessively load inner dual tire. Overloaded wheel bearings fail earlier than normal. Check for any grease lube leaks at the bottom of the axle housing . A split gasket (shown as the shaded area in Figure 5-4) almost always indicates an overload, or flex and housing distortion, which destroys the gasket between the carrier and the housing . NOTE: An overloaded (bent) axle housing will tend to wear the inner dual tires . Figure 5-4 - Bent Axle Housing SECTION 6 - BRAKES GENERAL DESCRIPTION BRAKES There are two brake systems on the motor home, the service brakes and the parking brakes . The service brakes use hydraulic pressure from a footpedal-operated master cylinder to actuate cylinders which apply the brakes at each wheel. Fluid lines and hoses connect the master cylinder with each of the wheel cylinders. When the brake pedal is depressed, force is transferred through the pushrod to the master cylinder primary piston, which moves forward . Under normal conditions, the combination of hydraulic pressure and the force of the primary piston spring moves the secondary piston forward at the same time . When the pistons have moved forward, hydraulic pressure is built up and transmitted through the brake hydraulic lines to the front and rear brake assemblies . Hydraulic pressure behind the wheel cylinder cups forces the pistons outward, causing the brakes to be applied. Braking action occurs as a result of friction between the brake lining material and the metal surface of the rotor disc or the drum. As brake pedal force is reduced, brake fluid pressure in the master cylinder is also reduced. This allows the drum brake retractor springs to retract the shoe and lining assemblies from contact with the drum which forces brake fluid out of the wheel cylinder assemblies and back into the master cylinder assembly. The reduction in fluid pressure also allows the disc brake caliper pistons to retract slightly by action of the piston seal . (See Figure 6-1 .) VACUUM BOOSTER MASTER CYLINDER FRONT BRAKE CALIPER HYDRAULIC LINES TO REAR-WHEEL BRAKES BRAKE ROTOR FRONT Figure 6-1 -Typical Hydraulic System SECTION 6 DISC BRAKES Upon application of the brakes, fluid pressure applied to the piston(s) is transmitted to the inner shoe and lining, forcing the lining against the inner rotor surface . The pressure applied to the bottom of the piston bore(s) forces the caliper to slide or move on the mounting bolts toward the inner side, or toward the vehicle . Since the caliper is one piece, this movement toward the vehicle causes the outer section of the caliper to apply pressure against the back BRAKES of the outer shoe and lining assembly, forcing the lining against the outer rotor surface . As line pressure builds up, the shoe and lining assemblies are pressed against the rotor surfaces with increased force, bringing the vehicle to a stop. (See Figure 6-2 .) Lining wear is automatically compensated for by the outward movement of the caliper and piston . Brake fluid fills this void as lining wears . CALIPER NOTE: OVERSIZE SUPPORT KEYS ARE AVAILABLE . REFER TO GM BULLETIN NO . 79-T-25 DATED JANUARY, 1980 (APPENDIX 6-1 AT THE BACK OF THIS SECTION) BOOT PISTON '~ INBOARD SHOE OUTBOARD SHOE CALIPER INBOARD SHOE AND LINING OUTBOARD SHOE AND LINING Figure 6-2 - Disc Brake 6-2 I CALIPER SPRING ANTI-RATTLE SPRING SECTION 6 BRAKES WHEEL CYLINDER SCREWS BACKING PLATE WHEEL CYLINDER LINKS SECONDARY SHOE & LINING SHOE GUIDE PARKING BRAKE STRUT STRUT SPRING ADJUSTER LEVER ACTUATING LINK -1 71 J OW NAAM 0 0 HOLD _1 DOWN PINS l0(( HOLD DOWN SPRING & CUP\ BRAKE SHOE RETURN SPRINGS ~ PARKING BRAKE LEVER `- WHEEL CYLINDER PRIMARY SHOE AND LINING HOLD DOWN SPRING ADJUSTING SCREW SPRING ADJUSTING SCREW LEVER RETURN SPRINGS I L ~-- Figure 6-3-Typical Brake Drum Assembly DRUM BRAKES When the brake pedal is depressed, fluid is forced through the brake lines into the piston . The wheel cylinder links are then forced out against the brake shoes which exert braking action on the drum . When the pedal is released, the return springs pull the shoes away from the drum. (See Figure 6-3 .) POWER UNITS Additional braking power is supplied through either a vacuum booster or a Hydro-Boost . The master cylinder is mounted on the forward end of the vacuum booster or Hydro-Boost . (See Figure 6-4 .) Figure 6-4 - Power Brake Hydro-Boost The Hydro-Boost utilizes hydraulic pressure supplied from the power steering pump. A spring accumulator is also included in the booster to provide reserve braking power in case pressure from the power steering pump is unavailable . At normal curb idle with 150 lbs. of pedal pressure, the Hydro-Boost could be expected to produce 1,600-1,850 lbs. of line pressure measured at any wheel cylinder bleeder port. Similar pressures could be expected of most vacuum boosters with good engine vacuum . 6-3 SECTION 6 BRAKES PARKING BRAKE(S) Customers have expressed concern with their ability to push the brake pedal to the floor with the vehicle stationary and the engine running . If the Hydro-Boost brake pedal is forced to the floor, as can be done, and the motion stopping function and effectiveness of the brake system is still considered normal, then the pedal travel action of the Hydro-Boost brake system is also considered to be normal . (See Pedal Travel Check in this section of the manual .) Both the G-Series and P-Series are equipped with a parking brake system . This system is mechanically operated by a lever and strut or a pedal which will activate the rear brakes only or the propshaft drum brake unit (P-Series motor homes with a GVWR of 14,000 lbs . or more) . Very little maintenance is required, but some periodic adjustment is necessary . (See Figure 6-5 .) P-SERIES CABLE TO REAR WHEEL BRAKES WITH REAR WHEEL PARKING BRAKES NOTE: WITH REAR DRUM OR PROPSHAFT DRUM PROPERLY ADJUSTED PROPER ADJUSTMENT OF THE OPERATOR ORSCHELN PULL HANDLE WILL REQUIRE 90 LBS . PULL OVER FORCE. WITH PROPSHAFT PARKING BRAKE Figure 6-5 - Parking Brake System See Figure 6-3 for typical brake drum assembly. 1 . Shoe Kit #1155270 ' Figure 6-6 I/ 2 . Drum &Flange #368008 6-4 SECTION 6 MAINTENANCE AND INSPECTION BRAKES LINING INSPECTION The -master cylinder is located under the floor on the driver's side of the engine (P-Series), or on the cowl (G-Series). The position of the master cylinder on the PSeries may require the use of a flashlight and mirror to check the fluid level . Inspect the brake linings per the vehicle Maintenance Schedule and anytime the wheels are removed (tire rotation, etc .) . Check both ends of the outer shoe by looking at each end of the caliper . Check the lining thickness on the inner shoe by looking down through the inspection hole in the top of the caliper housing . Whenever the lining is worn to the approximate thickness of the shoe, the shoe and lining should be removed . After removal, measure the lining thickness . The shoe and lining should be replaced anytime the lining is worn to within 1/32 inch of a rivet or of the shoe at any point, or when wear indicator contacts the rotor. Always replace linings in sets (both right and left front) . Thoroughly clean the reservoir cover before removal to avoid getting dirt into the reservoir . Remove the cover and diaphragm . Add fluid as required to bring the level to 1/4 inch (plus or minus 1/8 inch) from the lowest portion of the top of each reservoir . Use Delco Supreme No . II Hydraulic Brake Fluid (DOT No. 3) or equivalent. Some front disc brakes have a wear indicator that makes a noise when the linings wear to a degree where replacement is required. (See Figure 6-6 .) The spring clip is an integral part of the inboard shoe and lining . When the lining is worn, the clip contacts the rotor and produces a warning noise ., FILLING THE MASTER CYLINDER The master cylinder must be kept properly filled to ensure adequate reserve and to prevent air from entering the hydraulic system . However, because of expansion due to heat absorbed from the brakes and from the engine, the master cylinder must not be overfilled. Do not use shock absorber fluid or any other fluid which contains mineral oil . Do not use a container which has been used for mineral oil or a container which is wet from water . Mineral oil will cause swelling and distortion of rubber parts in the hydraulic brake system and water will mix with brake fluid, lowering the fluid boiling point . Keep all fluid containers capped to prevent water contamination . CAUTION : CHECK FOR LEAKS IF A LARGE AMOUNT OF FLUID IS REQUIRED. PEDAL TRAVEL CHECK At periodic intervals, the motor home owner should inspect the vehicle brake system for "pedal travel." Brake pedal travel is the distance the brake pedal moves toward the floor from the fully released position (foot not applied to the brake) . Brake pedal inspection should be made with the brakes "cold ." With the engine turned off, depress the brake pedal a minimum of four (4) times to exhaust all vacuum and/or accumulator pressure . Applying approximately 90 pounds of pedal pressure, the distance the brake pedal should travel is as follows : G-Series with power brakes . . . . . . . . . . . . . . . . . . . . 3.5 inches P-Series with drum rear brakes . . . . . . . . . . . . . . . . 3.5 inches P-Series with disc rear brakes (JF9) . . . . . . . . . . 6.0 inches BRAKE HOSE INSPECTION The flexible hydraulic brake hose which transmits hydraulic pressure from the steel brake pipe on the frame to the rear axle and to the calipers should be inspected regularly in accordance with the vehicle Maintenance Schedule . The brake hose assembly should be checked for road hazard damage, for cracks and chafing of the outer cover, and for leaks and blisters . A light and mirror may be needed for an adequate inspection. If any of the above conditions are observed on the brake hose, it will be necessary to replace it. Figure 6-7 - Disc Brake Wear Indicators Check the flatness of the brake pads. Place inboard and outboard pad surfaces together and check for a gap between the pad surfaces . If more than a .005-inch gap is measured at the middle of the pad (midway between attaching lugs), the pad must not be used. This applies to new or used brake pads. Whenever the front disc brakes are relined, the rear brakes should also be checked . BRAKE DRUM INSPECTION Whenever brake drums are removed, they should be thoroughly cleaned and inspected for cracks, scores, deep grooves and out-of-round condition . A cracked drum is unsafe for further service and must be replaced . Do not attempt to weld a cracked drum . SECTION 6 - BRAKES BRAKE CALIPER NOISE Smooth up any slight scores . Heavy or extensive scoring will cause excessive brake lining wear, and it will probably be necessary to turn the drum on a lathe in order to true up the braking surface . Sometimes on vehicles with high mileage, a noise or rattle condition caused by wear at the brake caliper and knuckle slide surfaces may be encountered . This condition does not affect the operation of the brake system, but the noise or rattle condition can be corrected by installing an oversized key and spring available as a service replacement. GM Bulletin 79-T-25 (Jan . 1980) in Appendix 6-1 at the back of this section provides details for selecting the proper size replacement key and how to install the key. If the brake linings are slightly worn and the drum is grooved, the drum should be polished with fine emery cloth but should not be turned . At this stage, eliminating the groove in the drum would necessitate removal of too much metal, while if left alone, the grooves and lining ridges match and satisfactory service can be obtained . BRAKE PEDAL/STOPLIGHT ADJUSTMENT NOTE: The adjustments listed below do not change with time or miles . An incorrect adjustment would normally be noted in the first few miles of vehicle life or after service work of some kind performed under the dash resulting in system malfunction . If brake linings are to be replaced, a grooved drum should be turned for use with new linings . A grooved drum, if used with new lining, will not only wear the lining, but will make it difficult, if not impossible, to obtain efficient brake performance . 1 . Check for a full upward and full release of the brake pedal. Determine if the stoplight switch, cruise control switch or any other item does not allow full upward pedal travel. (See Figure 6-7 .) The stoplight switch/ brake pedal mounting bracket provides automatic adjustment when the brake pedal is manually returned to its mechanical "up-stop" position . An out-of-round drum makes accurate brake shoe adjustment impossible and is likely to cause excessive wear of other parts of brake mechanism due to its eccentric action . An out-of-round drum can also cause severe and irregular tire tread wear as well as a pulsating brake pedal . When the braking surface of a brake drum exceeds the factory specification limits in taper and/or being out of round, the drum should be turned to true up the braking surface . 2. Pull the brake pedal fully rearward against the pedal stop until audible "click" sounds can no longer be heard . This moves the stoplight switch assembly in a tubular clip, as shown in Figure 6-7, and provides a proper adjustment. BRAKE ROTOR INSPECTION To prevent brake roughness, the rubbing surfaces of the rotor must be flat, parallel and with lateral runout held to a minimum . The surface finish should be smooth to avoid pulling or erratic brake performance . Light scoring which results from normal use is not detrimental to brake operation if the scoring does not exceed .015 inch in depth . NOTE : Proper adjustment of the stoplight switch allows .06 inch to .36 inch free pedal travel and will turn on the stoplight switch after approximately .40 inch travel. (See Figure 6-8 .) Lateral runout, the side-to-side movement of the rotor as it rotates, if'excessive (over .004 inch total indicator reading), can cause vibration when the brakes are applied . It is checked using a dial indicator gage which a qualified service shop should have. CRUISE CONTROL ONLY (WITHOUT CRUISE CONTROL) DISC BRAKE SQUEAL OR SQUEAK A persistent amount of "squeal or squeak" is often associated with heavy-duty disc brake usage . These noises are common for both foreign and domestic disc brake systems . Heat, humidity and severity of usage seem to be contributing factors to brake noise . Changing the brake pads, or rotor refinishing as a repair, is often considered a temporary repair, or even, by some technicians as useless . The recommended aproach is to have an inspection to assure there is free and proper operation of all caliper, parts . At this point, the owner should realize that the brake noise exists, but is not detrimental to overall brake life. NOTE: Refer to bulletin section on pads that will help reduce brake noise on pre 1992 units. BRAKE PEDAL MOUNTING BRACKET (WITH CRUISE CONTROL) Figure 6-8 - Brake Pedal/Stoplight Switch Assembly 6-6 SECTION 6 3. Check the 31-inch rod that runs down the front of the chassis and connects the brake pedal to the HydroBoost for proper adjustment. (See Figure 6-8 .) The rod can be adjusted (longer or shorter) using the screw adjustment located at the bottom of the rod . Block the wheels and hold the inside pedal in the "full-up" position . Check that there is free entry of the special bolt through the relax4d pedal rod lever connecting the linkage into the Hydro-Boost . Turn the adjustment screw to lengthen or shorten the rod as necessary. 4. Tighten the adjusting lock nut to 22-30 ft. lbs. then tighten the nut on the special bolt and install a new cotter pin . NOTE : Newer model rods can not be adjusted. BRAKES NOTE : The following procedure is for manual bleeding of the brakes only. If possible, obtain approved commercial pressure-bleeding equipment or the GM Tools Vacuum Brake Bleeder . (See the GM Wheel Service System Brake Bleeder in Appendix 6-2 at the back of this section for further information regarding Brake Bleeder specifications, usage and ordering information .) With power brakes, remove the vacuum reserve by applying the brakes several times with the engine off . Then, complete the following steps: 1 . Fill the master cylinder reservoirs with brake fluid and keep at least one-half full of fluid during the bleeding operation . (See Figure 6-1 .) 2. If the master cylinder is known or suspected to have air in the bore, then it must be bled (before bleeding any wheel cylinder or caliper) in the following manner: a. Disconnect the forward (blind end) brake pipe connection at the master cylinder. PEDAL BUMPER .06" TO .36" FREE PEDAL TRAVEL b. Allow brake fluid to fill the master cylinder bore until it begins to flow from the forward pipe connector port. c. Connect the forward brake pipe to the master cylinder and tighten . .40" PEDAL TRAVEL REQUIRED TO TURN STOPLAMP SWITCH ON PEDAL ROD LEVER PEDAL ROD END Figure 6-9 - Actuating Rod/Brake Pedal/Stoplight Adjustment BLEEDING BRAKE HYDRAULIC SYSTEM A bleeding operation is necessary to remove air whenever it is introduced into the hydraulic brake system . It may be necessary to bleed the hydraulic system at all four wheel cylinders if air has been introduced through low fluid level or by disconnecting the brake pipes at the master cylinder. If a brake pipe is disconnected at any wheel cylinder, then that wheel cylinder only needs to be bled. If pipes are disconnected at any fitting located between the master cylinder and wheel cylinders, then all wheel cylinders served by the disconnected pipe must be bled. d. Depress the brake pedal slowly one time and hold. Loosen the forward brake pipe connection at the master cylinder to purge air from the bore. Tighten the connection and then release the brake pedal slowly. Wait 15 seconds . Repeat the sequence, including the 15-second wait, until all air is removed from the bore. Care must be taken to prevent brake fluid from contacting any painted surface. e. After all air has been removed at the forward connection,, bleed the master cylinder at the rear (cowl) connection in the same manner as the front, as in Step "d" above . f. If it is known that the calipers and wheel cylinders do not contain any air, then it will not be necessary to bleed them. 3. Individual wheel cylinders or calipers are bled only after all air is removed from the master cylinder. a. Place a proper size box-end wrench over the bleeder valve . Attach transparent tube over valve and allow tube to be hand submerged in brake fluid in a transparent container . Depress the brake pedal slowly one time and hold. Loosen the bleeder valve to purge the air from the cylinder. Tighten bleeder screw and slowly release pedal. Wait 15 seconds . Repeat the sequence, including the 15-second wait until all air is removed . It may be necessary to repeat the sequence ten or more times to remove all the air . SECTION 6 BRAKES 4 . If it is necessary to bleed all of the wheel cylinders and calipers, the following sequence should be followed : 1) Right-rear wheel cylinder; 2) Left-rear wheel cylinder ; 3) Right-front caliper ; 4) Left-front caliper . c. Check the reservoir fluid level, filling it to the proper level if necessary, following operations 1 through 10. This step and step "d" are extremely important as low fluid level and/or air in the fluid are the most frequent causes of objectionable pump noises . 5. Check the brake pedal for "sponginess" and the brake warning light for indication of unbalanced pressure . Repeat entire bleeding procedure to correct either of these two conditions. d. Check for the presence of air in the fluid. Air will show up as a milky-looking fluid. If air is present, attempt to bleed the system as described in operations 1 through 10. If it becomes obvious that the pump will not bleed after a few trials, refer to the appropriate shop manual for more detailed test procedures . BLEEDING HYDRO-BOOST BRAKE SYSTEM Whenever the booster is removed and reinstalled, the steering system should be bled as outlined below. NOTE: Power steering fluid and brake fluid cannot be mixed. If brake seals contact steering fluid or steering seals contact brake fluid, seal damage will result. 1 . Fill fluid reservoir to the proper level and let the fluid remain undisturbed for at least two minutes. 2. Start the engine and let it run momentarily . 3. Add fluid if necessary. 4. Repeat above procedure until the fluid level remains constant after running engine . 5. Raise front end of the vehicle so that the wheels are off the ground . 6. Turn the wheels (off ground) right and left, lightly contacting the wheel stops . 7. Add fluid if necessary. 8. Lower the vehicle . 9. Start engine and depress the brake pedal several times while rotating the steering wheel from stop to stop . 10. Turn engine off and. then pump the brake pedal 4-5 times to deplete accumulator pressure. 11 . Check the fluid level and refill as required . 12. If fluid is extremely foamy, allow vehicle to stand for a few minutes with the engine off and repeat above procedure . a. Check belt tightness and check for a bent pully. (Pulley should not wobble with engine running .) b. Check to make sure hoses are not touching any other parts of the vehicle, particularly the sheet metal . 13. The presence of trapped air in the system will cause the fluid level in the pump to rise when the engine is turned off. Continue to bleed the system until this condition no longer occurs . POWER BRAKE UNITS The hydraulic lines connecting the power steering pump, Hydro-Boost unit and steering gear, as well as the components themselves, should be checked regularly for signs of leaks, damage or deterioration on vehicles so equipped . For vehicles with vacuum boosters, inspect the vacuum hoses and booster chamber for damage or deterioration . NOTE: Power steering fluid and brake fluid cannot be mixed . If brake seals contact steering fluid or steering seals contact brake fluid, seal damage will result. Both the vacuum booster and Hydro-Boost should be serviced by a qualified repairman . PARKING BRAKE Adjustment of the parking brake cable is necessary whenever holding ability is not adequate or whenever the center brake cables have been disconnected . An improperly adjusted parking brake cable may also cause the brakes to drag. On 16,000# GVW units, the transmission must be in neutral . The service brakes must be properly adjusted as a base for parking brake adjustment ; conversely, the parking brake must be properly adjusted for the service brake to function as intended . Inspection If a complete release of the parking brake is not obtained, unless it is forcibly returned to its released position, or if application effort is high, check parking brake assembly for free operation . If operation is sticky or a bind is experienced, correct as follows : 1 . Clean and lubricate brake cables and equalizer with Delco Brake Lube (or equivalent) . 6- 8 SECTION 6 - BRAKES 2. Inspect brake assembly for straightness and alignment (replace if necessary). 3. Loosen nut at intermediate cable equalizer and then adjust nut to give light drag at rear wheels . (See NOTE at the end of this procedure .) 3. Clean and lubricate parking brake assembly with Delco Brake Lube (or equivalent) . 4. Readjust parking brake lever knob to give a definite snap-over-center feel . Proper pull-over force is 90 pounds . 4. Check routing of cables for kinks or binding . NOTE: This fastener is an important attaching part in that it could affect the performance of vital components and systems, and/or could result in major repair expense . It must be replaced with one having the same part number or with an equivalent part if replacement becomes necessary. Do not use a replacement part of lesser quality or substitute design ; Drum Balance An imbalanced parking brake drum can cause vibrations . If a vibration occurs, perform the following to check for an imbalance problem with the parking brake drum : 1 . Place the transmission into NEUTRAL and increase the engine speed to the approximate speed that the vibration is felt while driving the vehicle on the road . Propeller Shaft Drum-Type Brake Adjustment (Adjustment - Drum On) 2. If the vibration has disappeared, check the parking brake drum on the back of the transmission if so equipped. Refer to Figure 6-9 . 1 . Using a jack, raise vehicle so that at least one rear wheel is off ground . Block wheels and release the hand brake. 3. Disconnect the propeller shaft at the back of the transmission and remove the drum . 4. Retest as in Step 1; If the vibration is gone, replace the drum . (See Figure 6-9 .) 2. Remove cotter pin and clevis pin connecting the pull rod and relay lever . This will assure freedom for full shoe release . NOTE: If a strobe light wheel balancer is available, position the strobe pick-up against the transmission pan . Adapt the procedure listed in the Driveline Balance section of this manual to check for a balanced drum. Add weight under the retaining bolt of the parking brake drum as necessary . NOTE : It may be necessary to knock out lanced area in brake drum (or backing plate) with punch and hammer to gain entry to adjusting screw through brake drum . Be sure to remove any metal that has fallen inside the parking brake drum. Cable Adjustment FOOT PEDAL TYPE (G-P series) - Before adjusting parking brake, check service brake condition and adjustment. 1 . Loosen the equalizer adjusting nut . 2. Apply parking brake four notches from fully released position. Only 1 notch on P series . 3. Rotate brake drum to bring one of the access holes into line with adjusting screw at bottom of shoes (manual transmission), or top of shoes (automatic transmission) . 4. Expand shoes by rotating adjusting screws with a screwdriver inserted through hole in the drum . Move outer end of screwdriver away from the drive shaft. Continue adjustment until shoes are tight against drum and drum cannot be rotated by hand. Back off adjustment and check drum for free rotation . 3. Tighten the equalizer nut until a moderate drag is felt when the rear wheels are rotated forward . (See NOTE at the end of this procedure .) 5. Place parking brake lever in the fully released position . Take up slack in the brake linkage by pulling back on cable just enough to overcome spring tension . Adjust clevis of the pull rod or front cable to line up with hole in the relay levers . 4. Fully release parking brake and rotate the rear wheels. No drag should be present . a. Insert clevis pin and cotter pin,-then tighten clevis locknut . ORSCHELN LEVER TYPE (P-SERIES) - b. Install anew metal hole cover in drum to prevent contamination of the brake. 1 . Turn adjusting knob on parking brake lever counterclockwise to stop. 2. Apply parking 6-9 c. Lower rear wheels . Remove jack and wheel blocks. See Note under Cable Adjustment procedure in this section . SECTION 6 BRAKES AUTOMATIC APPLY PARKING BRAKE 1990 P3 MOTOR HOME (16,000# GVW ONLY) The parking brake system on the 199016,000 pound GVW P3 motorhome chassis incorporates a unique automatic apply feature with an internal expanding parking brake. The system is different than the 1989 and 1991 systems of the same model . The parking brake is spring applied and hydraulically released. Hydraulic pressure is supplied by the power steering pump. Full brake disengagement requires that 95-115 PSI pressure exist at the brake actuator . The parking brake can be applied by using a hand button or automatically when the shift lever is in the park position . The system features an HR-1 relay valve serving as a flow control point. The HR-1 reduces and directs flow to and from a spring actuator operating the parking brake (See Figure 6-10) . Hydraulic System (Fig . 6-10) Steering fluid under pressure is supplied from the power steering pump which is then routed through the brake Figure 6-1 0 hydro-boost unit on to the power steering gear to port #1 of the HR-1 relay valve thus pressurizing the system . All fluid is then directed back to the power steering pump by way of port #2 on the relay valve . Pressurized fluid is then directed to port #3 of the HR-1 relay valve where it is held at port "A" of the manual apply control valve . Fluid (assuming the shift selector lever is not in the "park" position) is directed out of port "B" of the manual valve to port °D" of the shift actuated control valve. Ports "C" on the manual valve and "F" on the shift valve are used to exhaust fluid and direct it back to the power steering pump reservoir and are always at zero pressure. Port "E" on the shift control valve is used as a "signal" pressure (fed to port #4 of the relay valve) to shuttle the relay valve to either channel pressurized fluid to or exhaust it out of the hydraulic brake actuator (port #5 of the relay valve) thereby releasing or applying the park brake assembly . SECTION 6 - BRAKES Various modes of operation are as follows : Vehicle in park, engine running, manual apply control valve in the "released" position (Fig. 6-11) Pressurized fluid is directed from port #3 of the relay valve to port "A" of the manual valve, on through the manual valve to its port "B" and then on to port "D" is blocked and prevented from entering the valve . Also, ports "E" and "F" are now hydraulically connected . With this connection, any Figure 6-1 1 fluid that was previously pressurized at port #4 of the relay valve, is allowed to pass through the shift valve and exhaust back to the power steering pump reservoir . With the lack of pressurized fluid at port #4 on the relay valve, pressurized fluid from port #1 of the relay valve is blocked inside of the valve preventing it from reaching port #5 and charging the brake actuator . Ports #5 and #6 of the relay valve are now internally connected. This allows the fluid in the brake actuator to exhaust through the relay valve and on to the power steering pump reservoir. With no hydraulic pressure at the actuator, spring pressure is free to apply the park brake. SECTION 6 BRAKES actuates the relay valve which blocks the connection of ports #5 and #6 in the relay valve and prohibits the exhausting of the brake actuator. Ports #1 and #5 of the relay valve are internally connected allowing pressurized fluid to be Ports "E" and "F" of the shift valve are not hydraulically directed to the brake actuator which forces the actuator connected . Port "E" is connected with port "D" directing a spring to be compressed and the park brake to release . signal feed to port #4 of the relay valve . This signal feed .Vehicle in any gear position other than "park", engine running, manual apply control valve in the "released" position (Fig. 6-12) Figure 6-1 2 SECTION 6 BRAKES Vehicle in apy gear position other than "park", pressurized fluid from port #1 to port #5 in the valve and engine running, manual apply control valve opening the passage between ports #5 and #6 allowing the fluid from the actuator to exhaust. With no pressurized fluid in the "applied" position (Fig. 6-13) over and to release the actuator, spring pressure takes Ports "A" and "B" of the manual valve are not connected . applies the park brake. Pressurized fluid at port "A" is blocked, preventing it from entering the valve . Ports °B" and "C" are hydraulically Operational Features connected . This allows any fluid that was previously directed to port ""D'" of the shift valve to exhaust back to the 1 . In the event the vehicle stalls, the wheels can be spun freely for at least ten minutes until pressure is drained power steering pump reservoir . With no pressurized fluid from the brake actuator and the spring brake reapplies . available at port "ID" of the shift valve, no signal feed can be supplied to port #4 of the relay valve (via the internal connection between ports "D" and "E" of the shift valve 2 . A parking brake light in the vehicle warns the operator based on the position ofthe shift valve) . This lack of a signal when the brake is applied . This brake light will come on feed allows the relay valve to actuate, blocking the flow of when the pressure at the actuator is less than 60 PSI . Figure 6-1 3 SECTION 6 BRAKES AUTOMATIC APPLY PARKING BRAKE 1991-1993 P3 MOTOR HOME (16,000# GVW ONLY) The parking brake system on the 1991 and 1993 16,000 pound GVW P3 motorhome chassis incorporates a revised system from the 1990 . The Park position brake is spring applied and hydraulic released, the same as 1990. The 1991-93 system incorporates a manual Parking brake pedal which applies the system when the shift indicator is in any position other than Park. the relay valve, this triggers a release of pressure from port "D" of the relay, valve through port "ER" to the reservoir . This allows the spring controlled actuator to apply the parking brake. The spring will apply the brake by traveling as far as the brake adjustment demand requires to balance brake apply and spring force. With the shift selector in park; Engine running ; and the manual foot lever in the released position, fluid will flow from the steering gear to port "SR" on the relay valve, through the relay valve and out port "TW" to the control valve supply port "SC" . Once the system is charged, the pressure should range between 130 and 150 psi . Any excess fluid will be discharged through port "R" back to the pump. The supply port or charge port "SC" is blocked off due to the control valve position in the park mode. When the valve is released from the park position, the fluid charge at the shift control valve port "SC" is diverted to port "DC". The shift control port "EC" is blocked off. The fluid charge at the relay valve port "SR" is diverted to port "D", this pressurizes the parking brake system and actuator. The fluid pressure working against the spring pressure in the actuator releases the parking brake. Any previously built pressure in the control valve flows through the control valve out port "EC" back through 70 . 71 . 72. 73 . 1. 2. 3. 4. 5. 6. 7. 8. 9. 10 . 70 Bolt Actuator Air Bleed Actuator Inlet Pipe Seal 74 . 75 . 76 . 1. The manual foot lever should still be applied whenever the vehicle is shifted into park. This will alert the driver of the need for adjustment in the parking brake system. 66. 67. 77. 78. 79. Connector Actuator Inlet Pipe Actuator Bracket Parking Brake Cable Power Steering Pump Reservoir Parking Brake Pedal Actuator Parking Brake Pressure Switch Control Valve Relay Valve 10 Steering Gear Master Cylinder 77 78 Parking Brake Control Rod Steering Column Transmission Control Equalizer Jam Nut Control Valve Lever SR - Supply to Relay Valve TW - Supply to Control Valve R - Return to Pump TWE - Control Valve Exhaust ER - Exhaust to Reservoir D - Delivery to Actuator C - Control Signal DC - Delivery From Control Valve SC - Supply to Control Valve EC - Exhaust From Control Valve 6-1 1 SECTION 6 29 28 BRAKES 43 . 44 . 45 . 46 . 47 . 48 . 49 . 50 . 51 . 52 . 56 . Removinglinstalling Parking Brake Pedal on P Motorhome Models 31 Actuator Cable P-Motorhome Model Clevis Pin Relay Lever Assembly Clevis Pin Washers (3) Washers (2) Cotter Pin 52 Cotter Pin Front Parking Brake Cable Clevis Pin Cotter Pin Bracket 50 28. 29. 30. 31 . 32 . Bracket Bon Parking Brake Pedal Brace Nut 43 Relay and Control Valve 64 . 65. 66 . 67 . 68 . 69 . P-Motorhome Model Cable Components 50 . 43. 53 . 54. 55 . 56. Front Parking Brake Cable Actuator Cable Brake Drum Actuator Bracket Bolt and Clip Bracket 6-1 2 Bolt Control Valve Parking Brake Control Rod Steering Column Relay Valve Nut APPENDIX 6-1 BRAKE CALIPER NOISE 3. Lay a straight edge across the forward caliper surfaces "C" and "D" (shown in the following illustration) and measure with a feeler gage the,maximum depth of any wear on these surfaces. Calipers worn to a depth of .050 inch or more should be replaced . Reference : General Motors Dealer Service Technical Bulletin No. 79-T-25 (January, 1980) 1974-1979 G-, P-30 Series Models with JB-8 or JF-9 Brake Option The following information has been extracted from the above mentioned bulletin . A noise or rattle condition caused by wear at the brake caliper and knuckle slide surface may be reported on some high-mileage vehicles as a loose or rattling front end on all but smooth roads. This condition does not affect the operation of the brake system . The J13-8 and JF-9 brake systems have a caliper retention design which incorporates a key and a leaf spring retained in a "V" groove . Vehicles which have the caliper rattle condition can be corrected by installing an oversized key and newly designed leaf spring available from General Motors Parts Division. The service keys will be available in five sizes (at .040-inch increments) to compensate for varying degrees of wear. Follow the procedure given below for correction of complaint vehicles: 1 . Remove caliper from knuckle by unscrewing key retention screw and tapping out key and spring. 2. Clean surfaces "A", "B", "C", and "D" (shown in the following illustration) with a wire brush, filing smooth any nicks and/or gouges . 4. Reinstall the caliper back into the knuckle . Install a new standard size key .and reinstall the key retention screw, but do not install the caliper support spring at this time . 5. Insert a screw driver into center of key/bumper gap and pry firmly to assure that caliper is seated against three slide surfaces -,"A", "B", "C .'' 6. Measure bumper gap with largest feeler gage (or stack of gages) that will fit into the gap for its full length . 7. Select a replacement key according to the table on page 6-12 . 8. Install selected replacement key and new design spring, GM Part No. 14023437, and reinstall retention screw . NOTE: " If retention screw is damaged or shows signs of excessive wear, replace with new part (GM Part No . 331478) . " The spring has been redesigned from a "C" to an "M" shape . The "M" spring must be installed with the large radius in contact with the key. 6-13 APPENDIX 6-1 BRAKE CALIPER NOISE (Cont'd) BUMPER GAP (IN .) MORE THAN BUT NOT" EXCEEDING 0 .060 Standard Size 1 14023439 .060 .100 .040 Oversized 11 14026793 .100 .140 .080 Oversized 111 14026794 .140 .180 .120 Oversized 1111 14026795 .180 .220 .160 Oversized 11111 14026796 .220 - REPLACEMENT KEY I.D. GM PART NO. Replace Anchor Plate/Knuckle and Caliper and use new standard size key and new spring . °C" SHAPE SPRING (OLD DESIGN) "M" SHAPE SPRING (NEW DESIGN) APPENDIX 6-2 VACUUM BRAKE BLEEDER The following information has been extracted from the GM Dealer Equipment Catalog . Vacuum brake bleeder features, specifications and ordering information has been described . FEATURES " Vacuum operation " Can be used for all types of cars, trucks, busses and motor bikes . " Fluid is retained in the canister, eliminating costly paint damage from splashing . " Brake set equipped with universal rubber connector on 40-inch quick-connect tubing and GM adapter . SPECIFICATIONS Air Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 CFM Minimum vacuum capacity . . . . . . . . . . . . . . . . . . . . . . . . . .60% Connection thread . . . . . . . . . . . . . . 1/4-inch female thread Canister volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 gal . HOW IT WORKS The brake bleeder is used as outlined below: 1 . Connect the brake bleeder to an air supply (80 to 175 PSI) and the hose with the rubber connector end to the brake bleed screw. 2. Depress the lever on the bleeder top to create a vacuum in the canister. 3. Apply a suitable wrench to the bleed screw, and open . Air and brake fluid will now be drawn out of the system. APPENDIX 6-3 BRAKE LINING LIFE EXPECTANCY VEHICLE #2 BRAKES APPLIED AT "X" VEHICLE #1 BRAKES APPLIED AT "Y" VEHICLE B .1U .'s fill B .TU .'s TOTAL HEAT GENERATED IN BRAKES IS THE SAME FOR BOTH VEHICLES 150 HP ABSORBED VEHICLE #1 ~10P 2 MMUJ I--x.900 HP ABSORBED -y AND VEHICLE #2 TRAVELING AT SAME SPEED WHEN BRAKES ARE APPLIED The following information is provided courtesy of GrayRock Company as an aid to the motor home owner in understanding brake lining life expectancy and premature drum failure . GM provides no statement as to the accuracy of this information, although it would appear to be correct . BRAKE DRUMS ON VEHICLE #1 DURING BRAKE APPLICATION A brake is a heat machine . A soft touch on the brakes pays off in any model vehicle in the form of brake life and fuel economy . Each time brakes are applied, you are converting forward motion (that you bought and paid for as fuel costs) into heat energy of stopping . Brakes change energy of motion to heat energy, and this energy is the same for any stop from a given speed. Many drivers take advantage of good brakes by stopping in shorter distances than necessary. The following example demonstrates improper braking techniques and the results . (See diagram above.) Assume both drivers (Vehicle No. 1 and No. 2) are operating identical vehicles and making a stop from the same speed . Vehicle No. 1 anticipates the stop and applies the brakes at point "Y" as shown in the diagram above . Heat is generated at a rate that the brakes of Vehicle No. 1 can handle - about 500°F at drum surface . The driver of Vehicle No. 2, shown in the diagram, doesn't apply his brakes until he reaches point "X." Although the work load on the brakes of both vehicles is the same, in the case of Vehicle No. 2, the work load is "poured" into the brakes in 1/6th the time. This means that the brakes must absorb 900 horsepower instead of just 150 . Vehicle No. 2 develops up to 2,000°F temperature at drum surface and at a rate faster than it can be transferred and dissipated. The result is short lining life and premature drum failure . 6-16 MINIMUM INPUT FOR SAFE STOP 500°F - NORMAL HEAT CONCENTRATION AT DRUM SURFACE BRAKE DRUMS ON VEHICLE #2 DURING BRAKE APPLICATION MAXIMUM INPUT "K FACTOR" WILL ALLOW 1800-2000°F - HIGH HEAT CONCENTRATION AT DRUM SURFACE SECTION 7 -- ENGINE ENGINE Your Chevrolet Motor Home Chassis is equipped with either the 5.7L or 7.4L (Mark IV) gasoline engine or the 6.2L diesel engine . Both the gasoline and diesel engines are four-cycle designs . That is, there are four distinct strokes (intake, compression, power and exhaust) in the power cycle of each. engine cylinder. The power cycle of a cylinder takes plce through two .revolutions of the crankshaft. NOTE: There is a "truck rule of thumb" that says, "For good engine life, the engine shall not cruise for long periods of time at speeds in excess of 80 90 percent of engine governed speed or as rated ." Full-rated speed is acceptable for short durations such as when the transmission is going through its shift points . The chart shown in Figure 7-1 shows the general relationship of engine speed to engine life. PRINCIPLES OF INCREASED ENGINE LIFE Avoid Engine Idling For Long Periods Of Time Long periods of engine idling will drop engine temperature and result in the incomplete burning of fuel. Raw unburned fuel can wash lubricating oil off cylinder walls and result in diluted crankcase oils and poor lubrication to all moving parts . High Operating Temperatures Increase Oil Oxidation Rate High engine temperatures that are caused by heavy loads, faulty cooling systems, incorrect timing, improper spark plugs, preignition and detonation, help to speed the oxidation of oils . Every 20 degree increase of temperature will double the oxidation rate. (See Figure 7-10.) Extreme heat causes the'oil to oxidize which forms tar and gum deposits inothe oil . Varnish will also form and result in ring sticking, valve sticking and malfunction of other vital engine parts . Clean oil coolers have proven successful in maintaining acceptable engine temperatures . Allow Engine To "Cool Down" Slightly Before Shut-Down If an engine has been heavily worked, it is a good policy to disengage the load from the engine and allow the engine to idle for a few minutes before turning off the ignition . This practice allows the engine to cool gradually and promotes a desirable dissipation of heat from any localized area of concentrated temperature . Such a practice avoids the rapid cooling that can cause warped valves, valve "tuliping," block distortion, cracked manifolds, etc. (See the Exhaust Manifold and Plug Wire Failure section for additional information, page 7-4 .) Figure 7-1- Engine Speed to Engine Life Water Temperature Is Important To Engine Operation And Engine Life Water temperature of 195 degrees Fahrenheit or higher assures that cylinder walls are heated to a proper temperature needed to support good combustion and that other working parts of the engine have expanded evenly to favorable clearances for oil lubrication . When water temperature , is too low, the cylinder walls retard the heating of air during compression and delay ignition . This causes incomplete combustion, excessive exhaust smoke, poor emissions, and high fuel consumption . Water Condensation In A Cold Engine Creates Unnecessary Engine Wear It has been well established that low operating temperature increases engine wear. The products of combustion in a "cold-running" engine combined with moisture will form a corrosive film of oxide on the cylinder walls and engine components. Engineers have estimated that as much as eight times the cylinder and engine wear occurs to an engine operating at temperatures to 100 degrees Fahrenheit compared to an engine operating at a temperature of 195 degrees Fahrenheit. SECTION 7 Avoid Initial "Scuffing" After Engine Rebuild After an engine has been overhauled, a pressurized oil system helps prevent damage to newly installed engine parts caused from a lack of lubrication. The system sends a supply of oil through the oil lines to the lifters, bearings, etc ., before the engine starts . Design engineers have approximated that' several hundred engine revolutions are required before the average lubrication system will supply the required amount of oil to the vital moving parts . This time lapse results because a normal oil pump must prime itself and then pump the oil throughout the system . If a newly overhauled engine is "dry" when started, the newly installed parts will be more sensitive to break-in abuse due to the high frictional temperatures caused by the momentary lack of oil . GASOLINE ENGINE Both the 5.71-(350 Cubic Inch Displacement) and the 7.41Mark IV (454 Cubic Inch Displacement) engines have eight cylinders and are designed to operate on no-lead gasoline . ENGINE Each is equipped with an electronic ignition system which has no breaker points or condenser . The system uses a spark plug in each cylinder to start combustion. Typical 7.41- engine ratings and basic specifications are shown in Figure 7-2 and 7-3 . DIESEL ENGINE The V-8, 6.21- diesel engine is similar to a V-8 gasoline engine in many ways but major differences exist in the cylinder heads, combustion chamber, fuel distribution system, air intake manifold and the method of ignition . The cylinder block, crankshaft, main bearings, rods, pistons and wrist pins are similar to those on a gasoline engine but are of a heavy-duty design because of the high compression ratio required in the diesel engine to ignite fuel. Ignition of the fuel in a diesel engine occurs because of heat developed in the combustion chamber during the compression stroke . Thus, no spark plugs or high-voltage ignition are necessary for a diesel engine . Typical 6.21- engine ratings and basic specifications are shown in Figure 7-4 . 1990-1994 1982-1989 Basic Specifications Engine type . . . . .. .. .. . . . . . . . Valve-in-head Piston displacement . . . (Liter/Cu .. . . In. ..) . . . . . . . . . . . . 7 .41454 Bore & stroke (nominal) . . . . . . . . . . . . . . . . 4 .25" x 4.00" Compression ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 .9 :1 Carburetor type . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Barrel Exhaust - Single . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . All Engine Ratings - Typical All States Heavy Duty Emissions (8501 lbs. GVWR and above) SAE net horsepower (77 °F) . . . . . . . . . . . 240 @ 3800 rpm SAE net torque ft-lb (77°F) . . . . . . . . . . . 375 @ 3200 rpm 250 ..... .. .............s... 240 I 230 ::: s40 230 520 220 500 220 : :cast 210 180 420 180 400 :a33 170 160 380 360 .H. : 150 340 140 320 130 300 120 280 110 260 100 240 80 ..3. ..-.--~ 200 460 440 190 180 170 180 z ~' ISO 3 0 140 N 130 C S 120 0 80 s0 70 160 60 0 I 4 I 8 ::ISilt I I I I I I I I 12 16 20 24 28 32 36 40 REVOLUTIONS PER MINUTE (+100) I 44 K F 100 200 70 m 110 220 :::.': ....3 .3 .339*. -500 210 460 200 50 Basic Specifications Engine type . . . . . . . . . . . . : . . . . . . . . . . . . Valve-in-head Piston displacement (Liter/Cu . In .) . . . . . . . . . . . . 7.4/454 Bore & stroke (nominal) . . . . . . . . . . . . . . . . 4 .25" x 4 .00" Compression ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 .9 :1 Carburetor type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TBI Exhaust - Single . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . All Engine Ratings - Typical All States Heavy Duty Emissions (8501 lbs . GVWR and above) SAE net horsepower (77 °F) . . . . . . . . . . . 230 (?a 3600 rpm SAE net torque ft-Ib (77 °F) . . . . . . . . . . . 385 Q 1600 rpm 60 160 $0 1 0 1 140 48 I 4 I 8 I 12 I 16 1 20 I 24 I 28 I 32 I 38 I 40 44 48 ENGII4E RPM (+100) Figure 7-3 - Typical 7.41- Engine Ratings and Specifications Figure 7-2 - Typical 7.4L Engine Ratings and Specifications 7-2 SECTION 7D Engine type . . . No . of cylinders Bore & stroke . . Displacement . . Injection pump . Brake HP . . . . . Peak Torque . . Comp . Ratio . . . . . . . . . . . . . . . . . . . ENGINE FUEL SYSTEMS Engine Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . Four cycle . . . . . . . . . . . . .. . . . . . . . .. . . . . .. . . .. . . 8 . . . . . . . . . . . . . . . . . . . . . . . . 4.06" x 3 .82" . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 cu . i n . . . . . . . . . . . . . Stanadyne Mechanical Type . . . . . . . . . . . . . . . 155 BHP @ 3500 RPM" . . . . . . . . . . . . . . . 285 lb . ft . @ 2000 RPM' . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 .3 :1 'HP and Torque range from 140HP/255 Ib . ft . to rating on chart . Performance Curve aaaaaa .. ...aa . ..ar " . ;,.aaa . .aaaa .a "aaaaaaaaaaa.aaaaaaaa . ._aaaaaa "" r " a.aaa.aaararr " aa """" i " .~ " rra "a " a "aaa .. """ aa . .r .""aa .a " .aaaaa """ aaaanow " a ""a "" raraarr "" aa "" r . one MOOMMEM us ".aaaa " aa Memo a """" aaaaaar .aa "". .aa " a . .aaa. .a .. . . .aarar . .a .. . . .a .a.rr 160 rraaaaaaaaaar.a " aaaaa . . " aa~-~aaa . " raaaaa """ aa " "" r "aaaa~~ . .a " aaaa 140 .ra . . ..a . .arar . .!i. . . . ..a .. .r . .a aaaaaaa " aaa . "ar :r.a .aaaa """" i "" a = 120 "" r. """"". """"." "a"""""" m HHHHaaa"UM "ar. . . aaa . "a .a .aaa aaa.aa .aa .r . 100 aara . """ rra "a .aa "" a.aaaar .aar "aa W aa ""aa "" ra "aa . " aaaaaar~ " aaa " ara".aa ..aaaaria .a . . .. .a .a.a .aas "a.a ..aon r, some HOME MMEMEMMONEVEMM 80 r as " ar~ .raar. . .aaar . .aaaa . " aaa. .a as " ar, . .raaa.a ..a .a .aaaa .aaa . " a " a 60 """ araa""" aa " rrara """ra """ aa "a " r aaa . . .r . .r .a .r . . . .a . .. .rr .a .ra .a a "" .a .. " a .aaaa ..a .aaaa .a . .aaa . .a 40 . .a .ara . ..r .a . .aaa. . .aaa . .a .a . .a "" aar "UM .r " aaa "" .rarrr. . .raarr" . " a sonso . . . ". .a .rr . . . .a ... .a . .a 1200 600 2000 2400 2800 3200 3600 ENGINE SPEED - RPM 300 280 260 240 220 Engine Specifications Engine type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Four cycle No. of cylinders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Bore & stroke . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 .98" x 3 .82" Displacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379 cu . i n . Injection pump . . . . . . . . . . . . . . . Stanadyne Mechanical Type Brake HP . . . . . . . . . . . . . . . . . . . . . . 190 BHP @ 3400 RPM' Peak Torque . . . . . . . . . . . . . . . . . . . 380 lb . ft . C 1700 RPM" Comp . Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 .5 :1 Combustion chamber . . . . . . . . . . . . . . . . . . . Indirect injection Turbo boost . . . . . . . . . . . . . . . . . . . . . . . . 10 psi @ peak torque Turbo mfgr. . . . . . . . . . . . . . . .. . . . . . . . . . . . . Borg Warner/11-11 R PO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . L65 H .D . engine Performance Curve W x POWER OUTPUT AT SAE J1349 conditions Figure 7-4 - Typical 6.21- Engine Ratings and Specifications .uuuarunun.uuuuoou .as .. .. .aaaa .raa ".aaaaa .aaa.aa.a a " argame. .soon "a ..aa "rr 400 240 ~aaaaaa""" nowaaaarr "" aa ""aar " rraaa a .raaaaa~a " aaa ." aaa .a" aa .r.aa "aa .. .ar:aaar.~rraa .a .aaa .. .a. .aa.a 350 oD 220 aaara. . . " aa .aaa .a i~~aa .ar .. . .r.a W raaara "" raaa ""a " raaa . ;,a "aaaaa300 "". " 200 """ a.-," "aa O=, ..ar .r .aa.aa. .. .r .r. ..aar". .aaa a "aara. .a "aa " aaa .aa .aa.a.r~. .araa "" a" aaa ""aaraa" .r .a.aaa:~a.aaraa a 180 r" aaraar "" aar "a """ a "" ~ "a ""rr""aa 250 a. .a ..aar. .a . .. . . . .r~ . . .r.r ..raa aa .aaaaaa" aa .a. .a a .aaaa.aaa ".a ." raa.HaaW ." . "Mara.. . ara . 160 a.r" rr " r """ar"""""rr . "" aa " rarar """a . a. " rara. ..a.aai~aaa """"" r.aara.a .~ uouv.oou . . . . a"a . ... a 140 aaaa ..aaaa .arraa. .. .aaaaaaaaa.aa. aa .r ." aaaai .aa .s a . .aaa . "a .aaa.a O a..a .aa..rir .a ..a ..aa.r .a..a ...a a ..raa .ar".r.a. .aa ..r .a. .rrr. .r .a 120 aas""" raar, aa "ra " r.ir" .. .raraa. .a .. .r .. .rr. .. .. . . .ar . .a .aa . . .ara r. .r . .ri .ara .. .a . ..r . . . . " ar. .. .r 100 . "ar.r~aaa . .ar.a.aaaaaaaaa .aaaaaa as" iri" sa. ". .aaaa "aa " aaaaa .aaaa. OMEN none Me@ 80 ar" ra .a .a . . .a.aaaaa "aaa "" .aaaaar .. .a ...aa .. .aaaaaa .a 60 .r ..a.aaa..a. """ aa " rr "" a "rar " aa "" aaara """""a . .aa.aa .raaaa.ra . ..arrrra .aaaaaa 1200 1600 2000 2400 2800 3200 3600 ENGINE SPEED - RPM POWER OUTPUT AT SAE J1349 conditions Figure 7-5 - Typical 6.51- Turbocharged Engine Ratings and Specifications SECTION 7D - ENGINE FUEL SYSTEMS GM's 6.51. V8 TURBO DIESEL ENGINE Serpentine Belt Drive The 6.51- features a single serpentine drive belt with an automatic tension adjuster which improves belt life. The Turbocharged system maintains the desired belt tension needed to run the integral components while allowing for the easy The 6.5L features a completely integrated Borg Warner/IHI replacement . turbocharger. This turbocharger is waste-gated on the exhaust side of the turbo with an all-new wastegate that is patented by GM and is specifically designed for this Draincock system . This new wastegate provides very tangible bene- Water Separator stress on the internal fits. By design, it reduces overall filter on engine components . To accomplish this, the wastegate is As the water separator an integral part of the fuel of draining off the water has been the 6.5L, the method designed to reduce turbo-boost pressure after maximum separator draincock . The water designed for convenience torque is obtained . This turbocharger delivers a top-boost allowing of 10 psi at 1700 RPM and produces outstanding respon- has been located up front on the top of the engine, when required . for easy draining sive acceleration on demand with no detectable turbo-lag . is Crankshaft Bearing and Seal The crankshaft bearings used in the 6.5L are made of a more fatigue resistant bearing material . This material promotes a higher stress life of the bearings. The rear crankshaft seal is a one-piece seal that greatly reduces the chances of leakage . Fuel Filtration System Optimized Combustion Chamber To provide smokeless performance and to meet stringent emissions standards without sacrificing power, the 6.51was designed with an optimized combustion chamber. This design provides an optimum balance of air in the prechamber in the head and of air in the cylinder. This balance of air enhances a more even and complete burning of the fuel. The double filtration fuel filter on the 6.51- combines the fuel filter, water separator and fuel heater all in one canister. Its Horsepower & Torque location and top-load vertical design allows easy filter cartridge replacement . The 6 .5L Turbo Diesel has a horsepower rating of 190 3400 RPM and a torque rating of 380 Lb.-ft . @ 1700 RPM, and provides a 30% torque rise over a usable 2800 RPM Design New Piston range. The 6.5L bulkhead area was designed to handle the higher cylinder firing pressures of a turbocharged engine. In addition the coolant passages and the oil galleries were sized to provide the increased flow required by a turbo engine . SECTION 7 EXHAUST MANIFOLDS There are three types of materials used in the various years and models of the G- and P-Series motor home chassis . Each material described below has specific features and drawbacks to be considered before being selected by the design engineer. " CAST IRON - Cast iron has been used for many years for the 454 CID engines including some current year engines . Cast iron is good for its ability to withstand heat and it is easy to produce and machine . However, a drawback to using cast iron a$ an exhaust manifold is that it can crack easily and has a slight tendency to warp. NODULAR IRON - Nodular iron has been used on many 350 CID and 454 CID engines . The nodular manifold is 5/16 in. thick versus 3/16 for the cast iron. Nodular iron has some of the same properties of cast iron but is not as prone to cracking . Also, nodular iron has less tendency to warp and become distorted than conventional cast iron. was removed . The more heat present when the manifold is removed, the greater the "apparent" shrinkage of the manifold . The manifold may be installed in the following manner: 1 . Install the two (2) center attaching bolts and torque the bolts to 10 ft. lbs. Install additional bolts if alignment is possible. 2. Connect the exhaust pipes, crossover pipe, etc . to allow the engine to "run." 3. Start the engine and allow the engine to run (5 to 12 minutes) until the manifold expands allowing easy installation of the remaining bolts . 4 . Torque the center bolts to a full 40 ft, lbs . torque and apply slightly less torque for each bolt as you proceed toward each end . (See Cast Iron Manifold Cracking section below for additional information .) NOTE: This procedure is not considered detrimental to the exhaust manifold in any way and can be used to save the expense of a new manifold. " STAINLESS STEEL - Stainless steel had come into use with some past production 454 CID engines with the new emissions Systems . Starting in 1985 midyear through 1989 federal and 1989 California. It is very difficult to produce and the materials cost is high. The net result is that the total cost of using stainless steel manifold vs. the manifold cast family itself is extremely high. CAST IRON MANIFOLD CRACKING With any manifold, the extremes of use are great. At one moment the manifold is 40 degrees Fahrenheit below zero and a few minutes later the manifold itself is white hot . Or, the manifold is white hot and the vehicle goes through a water puddle and quenches the manifold . Any and all parts can withstand a given amount of cycles or use before failure. GM warrants exhaust manifolds as part of . the normal, published warranties with the realization that it is very possible to produce a defective manifold . However, in instances where repetitive failures occur, the owner and service technician should examine the actual applications of use as to the cause of the failure (i .e ., overload, road splash, poor air flow, incorrect bolt torque, incorrect parts or improper installation) . NOTE: Experience shows that installing exhaust manifold gaskets rather than resurfacing the manifold is only a short time repair . Leaking manifolds should be resurfaced or replaced and do not use a gasket but use anti-seize compound #1052771 to increase manifold life. SERVICE TIPS NODULAR IRON MANIFOLD SHRINKAGE ENGINE At times a service technician may experience a problem with replacement of a manifold after it has been removed for service . The technician is unable to reinstall the attaching bolts due to shrinkage of the manifold. This complaint is a result of heat present at the time the manifold Before installing a new manifold, the dowel pin holes and bolt holes should be increased 1/32 inch in diameter to enable the manifold to expand and contract without buckling . The reason for this is that in some of the larger engines, the manifold actually increases in length as much as 1/8 inch when going from atmospheric temperature to operating temperature . Apply a liberal amount of anti-seize compound #1052771 to the manifold face and head face to increase manifold life . The compound appears to create a hard slate-like film with a very low coefficient of friction allowing the manifold to expand and contract and can be purchased through any Chevrolet dealership parts department . When installing a manifold on 454 engines, torque the center bolts to a full 40 ft. lbs . torque and slightly less torque for each bolt as you proceed towards either end . NOTE : If the bolts are not tightened enough, leaks will occur. If the bolts are overtightened, the manifold cannot expand and will buckle . Use a torque wrench whenever possible. CAST IRON WARPING Often times a warped cast iron manifold is caused by loose, poorly torqued attaching bolts or a broken attaching bolt. If the manifold is not held firmly against the block for proper heat absorption, exhaust heat can add to a warpage problem. The repair procedure may not require the manifold to be replaced providing a quality machine shop can resurface the face of the manifold flat . This can be an advantage as the cast iron has been "cured" with many heatings and coolings. Remachining the surface flat may actually be a better repair than manifold replacement . 7-3 SECTION 7 EXHAUST MANIFOLD AND PLUG WIRE FAILURE Chevrolet has determined that right side exhaust manifold and right side spark plug wire failure may be the result of inadequate air flow. This is due to the absence of a wheelwell panel on the right front wheel opening . This situation allows necessary engine cooling air flow to exit the engine compartment prior to passing the exhaust manifold and spark plug wires and therby cooling the manifold and spark plug wires as occurs on the left side of the engine compartment . See Figure 7-4 . ENGINE Care must be taken in the design of the right side panel as to provide proper clearances around any hoses, wires and engine dress items and also to provide clearance for the tire throughout its movements . The panel should extend rearward to a point parallel to the number seven spark plug wire. The panel should be shaped and positioned similarly to the left side panel currently installed on the vehicle . Care must be taken to leave an opening at the rear of the engine compartment to allow cooling air to exit the engine compartment as on the left side panel . See Figure 7-5 . The motor home owner should be advised that when stopping the vehicle for fuel fill or rest stops after sustained highway driving, the engine should be allowed to idle for a period of three to five minutes before turning off the engine . This "idle time" allows the cooling fans enough time to reduce and stabilize the underhood temperature thereby increasing effective component life (spark plug wires, exhaust manifolds, belts, hoses, etc .). EXHAUST MANIFOLD LEAKS Figure 7-4 - Inadequate Engine Compartment Air Flow This condition can be corrected by fabricating a metal panel similar to the one used on the left side of the vehicle . Adding the panel forces the air flow to pass along the right side of the engine compartment therby providing a cooling effect and greatly extends the manifold and spark plug wire life. See Figure 7-5 . Figure 7-5 - Corrected Engine Compartment Air Flow NOTE: Installation of the right hand engine heat splash shield GM Part #15680348 was implemented on 7-15-92 VIN #321432 see Figure 7-6-C. The following information is provided as an aid to the motor home owner of vehicles experiencing difficulty of both right and left exhaust manifold leaks . The information has been extracted from a Chevrolet Dealer Service Bulletin and intended to be used in conjunction with the right panel air flow correction described above . Reference : Chevrolet Dealer Service Bulletin No. 86-255 (November, 1987) `Some 1981-86 vehicles with 7.4L engines and cast iron manifolds may experience a condition where an exhaust leak develops between the manifold and the cylinder head mating surface causing a "noise condition ." Starting in 1987, an improved cast iron exhaust manifold using nodular iron instead of grey iron was released on the 1987 RV vehicles with the 7.41- engine . The nodular iron manifold is less susceptible to heat warpage than the previously used grey iron exhaust manifold . This manifold can be used to repair leaking exhaust manifolds on earlier year trucks and motor homes. This manifold is NOT interchangeable with tubular manifolds used with the H5D (Federal Emissions NA5/NA6 equipped trucks built after July 1, 1985, with Heavy Duty Emissions and dual air pumps) emission system . NOTE: To Install the improved manifold, parts in Figure 7-6-A are required . SECTION 7 ENGINE LEFT EXHAUST PIPE TO ENGINE OIL FILTER INTERFERENCE The following information was extracted from a Chevrolet Dealer Service Bulletin relating to left exhaust manifold header pipe redesign . Reference : Chevrolet Dealer Service Bulletin No. 86-250 (September, 1987) Figure 7-6 - Typical Manifold NOTE: A recent study by our engineering department has revealed that a substantial increase in exhaust manifold life can be obtained by cutting the manifold attaching support in 3 places between bolts #2 & 3 and 4 & 5 and 6 & 7 with a metal saw which allows each runner to move independently. See Figure 7-6. Some 1985-86 P-3 models equipped with a 7.4L engine and H5D emissions may exhibit a situation where the left exhaust manifold pipe contacts the oil filter. This condition was corrected (effective S.O.P. 1987) with the release of a redesigned exhaust manifold pipe. See Figure 7-6-B. This new pipe provides increased clearances between the oil filter and the exhaust pipe. PARTS INFORMATION IMPROVED CAST IRON MANIFOLD This new exhaust manifold pipe may be obtained through GM-SPO (GM Part No. 15559924) and may be used on earlier production vehicles manufactured with a 7.4L engine and H5D emissions . GM PART NO. USAGE 14103191 10045732 Manifold-Exhaust LH Manifold AssemblyExhaust RH Stud-Exhaust Manifold LH Stud-Exhaust Manifold RH Spring-Exhaust Manifold Nut-Exhaust Manifold (3/8-16) Washer-Exhaust Manifold (3/8-Flat) Seal AssemblyExhaust Manifold Bolt-Exhaust Manifold (3/8 x 1-3/16) Plug-Oxygen Sensor (18mm) LH Side Gasket-Oxygen Sensor Plug LH Side Shield-Starter Nut-Starter Shield (114-20) Anti-seize Compound 14053573 14053574 587575 9422297 120395 15592451 3909821 10017198 5617102 10068600 9439915 1052771 QUANTITY. 1 1 3 3 6 6 6 Figure 7-6-B - Redesigned Left Exhaust Manifold Pipe 2 16 1 1 1 2 1 NOTICE : THE RIGHT HAND MANIFOLD ASSEMBLY INCORPORATES A SHORTER HEAT STOVE . TO PROTECT STARTER WIRING, A HEAT SHIELD (GM PART NO. 10068600) MUST BE INSTALLED . Figure 7-6-C Figure 7-6-A 7-5 SECTION 7A ENGINE LUBRICATION ENGINE LUBRICATION pump pressure tries to pump oil through a clogged filter . When the pressure causes the bypass valve to open, the oil bypasses the filter and the engine continues to receive lubrication . Replacement of the filter at proper intervals will prevent damage to the engine due to a clogged filter . GENERAL DESCRIPTION The oil pan acts as a reservoir for holding the oil waiting to be circulated through the engine. The oil pan is attached to the bottom side or pan rail of the engine. A pressure-feed type pump is mounted to the bottom side of the rear main bearing cap . Extending down from the pump and into the oil, is a pickup tube with a screen cover to filter out foreign material. Oil is picked up by this tube and pumped through the gear-type oil pump. In the gasoline engines, the distributor, driven by a helical gear on the camshaft, drives the oil pump . For the diesel engine, the pump is driven from the engine camshaft by means of an intermediate shaft . The oil is next pumped from the engine and through a cooler located in front of the radiator which cools the oil and thus helps to remove engine heat (Figure 7-7). From the filter, the oil is pumped through the drilled galleries in the case to the various moving metal parts in the engine. After being pumped to the critical engine parts, oil drains back to the crankcase. Also, as the crankshaft rotates it slings oil off the crankpins to cover cylinder wall pistons, piston pin and piston rings. Oil drains off these parts and back to the engine pan . From the filter, the oil passes through a cooler. If this fullflow filter becomes clogged, the engine is equipped with a bypass valve which is spring loaded. This valve protects the engine from oil starvation byopening when increased There is also a second bypass valve. This is the oil-cooler bypass valve. It works much the same as the oil filter bypass valve and opens to allow an alternate route for the oil if the cooler should become clogged . There is an oil pressure switch which is assembled to the' top rear of the cylinder block to sense oil pressure in the main gallery . RADIATOR ENGINE OIL FILTER Figure 7-7-Typical Engine Oil Cooler Installation- Mark IV-1986 and Earlier 7-6 SECTION 7A - ENGINE LUBRICATION OILS Hot Weather QUALITY Engine oils are labeled on the containers with various API (American Petroleum Institute) designations of quality. For gasoline engines, Chevrolet recommends the use of an oil with the API designation "SG," either alone or shown with otherdesignations such as "SG/CC ." Oilswhich are not labeled "SG" should not be used. Fordiesel engines, Chevrolet recommends the use of oil designate of "SG/CE" or "SG/CD ." Other designations including "SG" alone should not be used for diesel engines . Using oils of a quality other than those recommended for Chevrolet gasoline and diesel engines respectively could cause engine damge . Cold Weather VISCOSITY Engine oil viscosity (thickness) has an effect on fuel economy. Lower viscosity engine oils can provide better fuel economy ; however higher temperature weather conditions require higher viscosity engine oils for satisfactory lubrication . Using any viscosity oils other than those recommended could cause engine damage . When choosing an oil, consider the range of temperature your vehicle will be operated in before the next oil change . Then, select the recommended oil viscosity from the applicable chart shown in Figure 7-8 or Figure 7-9 . GASOLINE ENGINES - For temperatures above 0°F, SAE 10W-30, is preferred for a single-choice multi-viscosity oil. However, for heavy-duty expressway driving in summer temperatures, there can be an advantage to a single-viscosity straight SG/CD 30 oil . NOTE : 10W-40 is missing from the chart shown in Figure 7-8 . 10VV-40 has been removed from all GM recommendations, because GM Research Labora tories have found generally a 1 .2% fuel economy penalty compared to 10W-30. Of the oils surveyed, some contained inadequate additives or even no additives and some did not meet the 10W-40 viscosity requirements . GM testing showed 10W-40 oils tended to be more prone to high mileage ring sticking. These problems appeared more frequently in 10W-40 oils than in 10W-30 oils. Figure 7-8- Oil Viscosity Chart-Gasoline Engine DIESEL ENGINES - For temperatures above 32°F, SAE 15W-40 is the preferred viscosity grade . SAE 30 oil can be used for continuous daily driving and all driving where the temperature will not be less than 32°F. These oils combine excellent film strength with the best available additive package to prevent wear and protect against piston ring sticking at higher mileages . DO NOT USE SAE 10W-40 oils in diesel engines, because most of them can cause piston ring sticking and engine damage . SAE 30 SG/CE and SF/CD oils are generally not suitable when temperatures fall below 32 0 F because of cold starting considerations . The use of SAE 15W-40 SG/CE or SF/CD at these lower temperatures (and in extremely cold areas SAE 10W-30 SG/CE or SF/CD) may be necessary. Hot Weather ,C . +38 +60 As a rule of thumb, in heavy-duty applications and sustained high-speed expressway driving, a single viscosity grade oil such as SAE 30 will be more satisfactory than multi-viscosity oils such as SAE 10W-30 . Multi-viscosity oils have an advantage of cold weather starting ease and better initial lubrication with cold engine oils . Notice that on the temperature chart shown in Figure 7-8, there is a trend away from the thinner viscosities as temperature goes up. The reason is that light oils do not have enough body for heavy-duty loads and high temperatures . +32 0 0 -18 -20 -2s SAE IoW-30 Cold Weather Figure 7-9 - Oil Viscosity Chart - Diesel Engine 7-7 SECTION 7A - ENGINE LUBRICATION Study the chart shown in Figure 7-9 carefully and follow its recommendations . As always, NEVER exceed the recommended oil change intervals since oil quality deteriorates rapidly with mileage, as carbon accumulates in the oil. SG/CD oils have generally proven to be the most successful oils in diesel applications . The diesel combustion process tends to produce sticking piston rings and high-sulfur fuels create problems that SG/CD chemistry is best suited to correct . Purchase fuels with a sulfur content of less than 0.4% . When sulfur content raises to between 0.4% and 1 .0%, it is a good practice to change oil at one-half the normal interval . When fuel sulfur content is above 1 .0%, oil should be changed at one-fourth the normal interval . SG/CE oils are generally best suited to gasoline engines . Gasoline engines do not have to cope with much of a sulfur problem and rarely develop ring sticking problems with proper oil change intervals . Gasoline engines, because of their temperatures and flat tappet cams, need oils of superior anti-wear properties and the SG/CE chemistry is much better for this application . TEMPERATURE Normal engine lube oil temperature in a heavy-duty truck engine is between the engine water temperature and 50 degrees above coolant temperature . When the temperature of the engine lube oil exceeds the temperature of the engine coolant by more than 50 degrees the engine lube oil cooler is not doing its job properly and requires immediate attention . Severe oxidation problems will occur to lube oils that are subjected to high heat and extended oil change intervals . The oxidation rate of lube oils doubles with each 20 degrees of increase in lube oil temperature . Also, oxidation occurs in lube oil that is not being used or is in storage . Figure 7-10 indicates the expected oxidation rate of a lube oil containing a moderate amount of oxidation inhibitor under temperature increases of 20 degrees . ENERGY CONSERVING OILS It is recommended that you select an oil not only of the proper quality and viscosity, but also a fuel-saving product. These oils can be found in dealer service departments, service stations and other retail stores. They are identified by words such as: "Energy Conserving," "Energy Saving," "Conserves Gasoline," "Gas Saving," "Gasoline Saving," "Friction Reducing," "Improved Gasoline Mileage," "Improved Fuel Economy" or "Fuel Saving," etc . Be sure the fuel-saving oil you choose is of the recommended viscosity and API designations . Some fuel-saving oils do not meet the requirements necessary for your vehicle's engine . SYNTHETIC ENGINE OILS Synthetic engine oils and conventional, mineral-oil-based engine oils have some similarities . They are both blends DEGREES F LIFE EXPECTANCY 70 100 years 90 50 years 110 25 years 130 12 years 6 months 150 6 years 3 months 170 3 years 1 .5 months 190 570.70 days 210 285 .35 days 230 142 .67 days 250 71 .33 days 270 35.66 days 290 17.83 days Figure 7-10 - Temperature vs. Oil Life Expectancy of base oils and additives . In fact, most of the additives used in synthetic engine oils, are identical to those used in conventional engine oils; in at least one so-called synthetic oil, mineral oil is used as the base. The mineral oil used in conventional engine oils is a mixture of hydrocarbons (hydrogen and carbon) obtained from crude oil pumped from the ground and refined by physical separation processes such as distillation and solvent extraction . The base oil used in most synthetic engine oils is obtained by chemical reaction processes involving materials produced from the same crude oil . For example, an acid and an alcohol can be obtained from crude oil and reacted to produce an ester - a commonly used synthetic base oil - which is a fluid composed of hydrogen, carbon and oxygen . The performance quality of a finished engine oil, either conventional or synthetic, depends on a careful selection of the base oil and additives to produce the desired characteristics . Chevrolet currently recommends the use of SG engine oil only. To determine whether an oiI meets SG quality requirements, engine dynamometer tests (called Sequence Tests) are run which evaluate the ability of the oil to prevent wear, deposits, and rust and corrosion, as well as thickening of the oil itself. The Sequence Tests have been carefully developed over many years to ensure that an SG engine oil will perform satisfactorily in car engines under a wide variety of service conditions . Oil change intervals are selected based on many miles of car test and field service experience . Oil quality, engine design, type of service, and change interval, must be carefully balanced to ensure satisfactory engine performance and durability. The current recom7-8 SECTION 7A ENGINE LUBRICATION mended oil change intervals apply to any SG engine oil, conventional or synthetic . " Operating in dusty areas Information currently available on synthetic oils does not justify. any additional lengthening of the oil change intervals. Any engine part failures caused by using an oil beyond the recommended change intervals will not be covered under the New Vehicle Warranty . MAINTENANCE AND INSPECTION To provide proper lubrication for the engine and to help prevent engine damage, the oil level should be checked periodically to ensure that there is an adequate amount of oil . Also, the engine oil must be drained and replaced with fresh oil, and the oil filter replaced at the intervals recommended in the appropriate Maintenance Schedule . CHECKING OIL LEVEL " Warm - The best time to check the engine oil level is when the oil is-warm, such as during a fuel stop. First, allow a minimum of 10 minutes for the oil to drain back to the oil pan . Then pull the dipstick out, wipe it clean and push it back down all the way. Pull the dipstick back out and look at the oil level on the dipstick . Some dipsticks are marked with "Add" and "Full" lines . Others are marked "Add 1 Qt." and "Operating Range ." In all cases, keep the oil level above the "Add" line . Push the dipstick back down all the way after taking the reading . Add oil if needed. " COLD -- If you check the oil level when the oil is cold, do not run the engine first . The cold oil will not drain back .to the pan fast enough to give a true oil level . A good method of checking oil is as follows : At the end of a day's driving, pull the dipstick out slightly from the tube so that the tube is not sealed by the cap at the top of the dipstick . Leave the dipstick in this position overnight . Before starting the engine again the following day, seat the dipstick and check the oil level. This method will allow the oil to drain down easily and provide a more accurate reading . Oil can be-drained from the engine through the drain hole in the bottom of the oil pan . Replacment oil is added through the fill tube at the top of the engine and near the radiator. Generally, the recommended oil change interval for heavy-duty service is 3,000 miles. More frequent intervals are recommended if any of the following severe operating conditions are encountered: " Frequent long runs at high speeds and high ambient temperatures " Idling for extended periods and/or low-speed operation " Operating when outside temperatures remain below freezing and when most trips are less than 4 miles (6 kilometers) . NOTE: Refer to the owner's manual and vehicle Maintenance Schedule for the oil type, viscosity and alternate change intervals recommended for the operating conditions encountered. CHANGING THE OIL FILTER The oil filter is a spin-on type which can be removed with a band-type filter wrench . The replacement filter should be installed and hand tightened following the instructions with the filter. 454 ENGINE OIL FILL CAPACITY The 454 engine used in the motor home has a crankcase capacity of six (6) quarts plus one (1) quart for the ACPF35 oil filter for a total of seven (7) quarts. The seven (7) quart system has been in place for many years. NOTE: Failure to allow sufficient time for the oil to drain back into the oil pan can give an erroneous "low oil" reading and the appearance of excessive oil consumption . This applies to both gasoline and diesel engines . Approximately 10 minutes are required for full drain-back . CHANGING THE OIL " Towing a trailer or car NOTE : After an oil and filter change, an incorrect dipstick reading could occur showing an overfill. Chevrolet has determined the problem to be in the dipstick and/or tube calibration . Through the process of converting to metric, several different parts sources, and some stack-up and assembly tolerance, it is difficult to fully understand the problem. Chevrolet has determined that there is not a durability problem with operating the seven (7) quart system down as much as two (2) quarts. Nevertheless, to comply with the original design criteria and for other technical reasons, it is recommended you verify the dipstick calibration . An accurate procedure is as follows : 1 . Drain the engine oil when hot and remove the oil filter. Allow 10 minutes for complete drain . 2. Install a new AC-PF35 oil filter and 6 quarts of oil . 3. Start engine and run 5 minutes and shut off and allow 10 minutes for oil to drain down from the heads . 4. Dipstick the engine 3 times, and with a small file, make a mark at the fluid edge in the dipstlck that will indicate the new "add oil" mark. 5. Add 1 quart of oil, let set 5 minutes and again dipstick the engine 3 times and make a mark at the fluid edge which will indicate the full mark. 7- 9 SECTION 7A DIPSTICK REPLACEMENT ENGINE LUBRICATION Some owners of the 1987 P-30 motor home chassis with 7 .4L carbureted engines may realize problems with the oil level indicator (dipstick) assembly. Problems include (1 .) the oil level indicator is difficult to reinstall or (2.) the gage shows an incorrect oil level. If these conditions are encountered, they can be corrected by replacing the oil level indicator (GM Part No . 10085674) . The new oil level indicator incorporates a "T" handle on the end and 'a twist on the shaft making it easier to install, and the new indicator has relocated oil fill level markings . APPENDIX 7-1 GUIDELINE FOR ENGINE OIL CONSUMPTION The following information has been provided as a guide to the motor home owner concerning engine oil consumption. GM has produced the following guideline based upon information developed by Detroit Diesel . Many attempts have been made byvarious manufacturers to establish how much oil consumption can be expected by the owner. Detroit Diesel established a series of charts that took individual engine families from the smallest to the largest . As an example, the smallest engine family (2-71) operating at 2,100 RPM could be expected in a 10-hour working period to use about one-half quart of oil: The largest engine normally used in stationary application (about seven feet high by nine feet long in an engine stand) is d 16-cylinder engine (called a 16V-71T) that normally uses 8 or 9 quarts of oil at 2,300 RPM in a 10hour working period. In a stationary application, a very accurate prediction can be made, because the engine generally runs at a given RPM, is of a known size and is doing a given task, so the operator can easily use the charts. Charts could be produced for gasoline engines just as well, but generally in the automotive industry most applications are not stationary uses. Rather, the normal highway usage includes everything from idle, to wide-open throttle, to pulling a trailer . You have learned from the Detroit Diesel information that the bigger the engine and corresponding horsepower the greater the thirst for oil and petroleum products . For the standard automotive application, General Motors has developed a graph illustrating the relationship between minimum acceptable engine oil consumption and fuel usage . (See Figure A7-1-1 .) Engines with oil consumption below the level indicated by the "acceptable" line are potential candidates for repair . Note that engines working harder, i .e. using more fuel, will have higher oil consumption . Heavy-duty trucks, for example, will not achieve the same level of oil economy as passenger cars and, therefore, should not be considered for repair at the same levels . i - MARGINAL OIL CONSUMIJTION - DIFFICULT TO DIAGNOSE / - POSSIBLE CAUSE: EXTERNAL LEAKS, MALFUNCrI01NING PCV / SYSTEM * MISSING, WORN OR MISLOCATED VALVESTEM SEALS - HIGH OIL CONSUMPTION -CAUSE NORMALLY IDENTIFIABLE - MAY INVOLVE 0 ANY OF THE ABOVE *PISTON, PISTON RING, OR BORE' SCORING OR WEAR " VALVE GUIDE SCUFF OR WEAR " MISSING OR BROKEN RINGS 10 15 20 25 FUEL MPG (MILES PER GALLON) Figure A7-1-1- Engine Oil Consumption vs. Fuel Usage 7-11 30 35 APPENDIX 7-1 GUIDELINE FOR ENGINE OIL CONSUMPTION (Cont'd) The graph shown in Figure A7-1-1 does not consider time as a factor, however, two time-related factors are involved: (1 .) Judgements of excessive oil consumption should not be made until the engine is fully broken in (approximately 5,000 miles) and (2.) A sudden or significant change in oil consumption (when operating conditions remain the same) should be considered when deciding if repair is justified . Engines with very high oil consumption normally have obvious, easily diagnosed causes . Scuffed bores, broken or overlapped rings, or worn valve guides or seals are typical examples . Engines with marginally high oil consumption (indicated by the darkened section of the graph in Figure A7-1-1) are very difficult to diagnose even after disassembly. In these cases, initial efforts to correct the complaint should be directed at replacement of easily accessible items like gasketed areas with heavy leakage, PCV valve or oil separator, or valve stem seals, and verifying that the owner is using the best weight engine oil for the operating temperature before starting heavy repair in the piston ring and bore area. Manufacturers of power piston rings state that piston rings in today's engines, control oil very effectively. If 1/10th of a drop of oil would be consumed per explosion when driving at 60 MPH, an eight-cylinder vehicle would use about 90 quart§ of oil on a 600-mile trip. The actual average consumption of oil per explosion in today's engines is from 1/1,000th to 2/1,000th of a drop. NOTE: If a service technician determines that your engine valve seals need replacement, the recommended seals for the 454 engine are the Orange VITON engine seals (GM Part No. 460527) . VITON is an extremely good material for heavy-duty usage and is standard in the 454 & 427 truck engine. SECTION 7B - ENGINE COOLING SYSTEM ENGINE COOLING SYSTEM GENERAL DESCRIPTION To remove the excess heat from the engine and to maintain normal engine operating temperatures, both of the gasoline engines, and the 6.21- diesel engine use liquid cooling systems . Components of a typical system include a pump, thermostat, radiator, coolant recovery tank and hoses. In operation, the pump circulates coolant through passages in the engine cylinder block and heads ,where it absorbs heat. The hot coolant flows out of the engine through a hose to the radiator . In the radiator, the coolant loses heat to the outside air circulating around the radiator core tubes. Cooled coolant then flows out of the radiator, through a hose back to the engine . The engines have pressure-type cooling systems with thermostatic control on coolant circulation . The cooling system is sealed by a pressure-type radiator filler cap which causes the system to operate at higher-thanatmospheric pressure . Using the pressure relief cap in conjunction with the overflow tank, the design intent is to assure a 100 percent filled radiator at all times with any air or bubbles being pushed out of the radiator into the overflow tank. However, if the coolant level is too low initially, the cycle between the system and reservoir will not take place. THERMOSTAT The thermostat consists of a restriction valve actuated by a thermostatic element to help regulate the operating temperature of an engine . This is mounted in the forward part of the intake manifold, under the coolant outlet on the 5.71and Mark IV gasoline engines and in the coolant crossover pipe located at the front of the engine on the 6.21- diesel (Figures 7-12 and 7-13) . Thermostats are designed to open and close at predetermined temperatures . The higher pressure raises the boiling point of the coolant which increases the cooling efficiency of the radiator . The 15-pound pressure cap used raises the boiling point of coolant to approximately 262°F at sea level . All models have a closed cooling system using a round pressure cap (Figure 7-11) and a coolant reservoir . Coolant can be added without removing the radiator cap. Figure 7-12 - Coolant Thermostat Location -7.4L Mark IV Gasoline Engine Figure 7-11- Radiator Pressure Cap A pressure-vacuum valve radiator cap (Figure 7-11) is used. As the engine warms up, pressure is developed due to the temperature expansion of the coolant . When pressure reaches the preset cap value (usually 15 PSI), the big spring compresses and the large gasket contacting the radiator neck unseats and allows the surplus coolant and air to flow into the coolant overflow tank. As the system cools upon shutdown, the coolant shrinks in volumetric size creating a partial vacuum in the radiator . This partial vacuum overcomes a small hidden spring and the very center relief valve of the cap unseats. Consequently, coolant from the overflow tank returns to the radiator to start the process over again . All Chevrolet engines have a pellet-type thermostat (Figure 7-14) which is used in the coolant outlet passage to control the flow of engine coolant . It provides fast engine . warm-up and regulates coolant temperature levels . A wax pellet or power element in the thermostat expands when heated and contracts when cooled . The pellet is connected through a piston to a valve. When the pellet is heated, pressure is exerted against a rubber diaphragm which forces the valve to open . As the pellet is cooled the contraction allows a spring to' close the valve. Thus, the valve remains closed while the coolant is cold, preventing circulation of coolant through the radiator, but allowing the coolant to circulate through the engine to warm it quickly and evenly . 7- 1 3 SECTION 713 - ENGINE COOLING SYSTEM would not reduce the maximum operating temperature 30 degrees . If an engine is overheating, it is obviously operating above both 165 and 195 degrees Fahrenheit. ENGINE COOLING FANS Both the 5- and 7-blade engine cooling fans tend to be very noisy and draw a lot of horsepower. By varying the fan speed, both horsepower losses and noise are lowered except in maximum cooling demand situations . According to numerous industry tests, maximum cooling is required less than five percent of the total vehicle time. With the fan operating on low speed 95 percent of the time, there is a reduction in noise level and substantial savings in fuel. The fan should be viewed as a two-speed fan - low and high speed . When in the hi-speed mode, the noise level will be more than double . Noise levels are somewhat logarithmic in nature. Viscous drive fans always provide some air flow across the radiator and air conditioning . This type of fan drive also helps maintain design temperature differential between inlet temperature and outlet temperature to a 10°F and 15°F differential at maximum engine speed and load. Good cooling system design avoids excessively cold coolant from going back into the bottom of the block. School bus engines will sometimes have heat shock problems because in addition to the radiator there are as many as four or five heater-and-defrosters and very long lines removing large amounts of heat from the coolant above and beyond the radiator capacity . Figure 7-13 - Coolant Thermostat Location 6.21. Diesel FLANGE PISTON The variable drive fan is controlled by a temperature-sensitive clutch . (See Figure 7-15 .) The clutch housing is constructed of lightweight metal which is filled with silicone oil and hermetically sealed . COIL SPRING WAX PELLET RUBBER DIAPHRAGM Figure 7-14 - Thermostat - Typical As the engine becomes warm the thermostat pellet expands and the thermostat valve opens, permitting the coolant to flow through the radiator where heat is passed through the radiator walls. This opening and closing of the thermostat valve permits enough coolant to enter the radiator to keep the engine operating temperature above the lowest operating value stamped on the thermostat . The engine thermostat is often the first item that is suspected and replaced when the engine overheat condition is encountered. The thermostat is only designed to keep the engine operating temperature above the thermostat minimum or rated temperature . It has no way to control temperature above this . If an engine is overheating, replacing a thermostat rated at 195°F with one rated at 165°F Thermostat control of the fluid clutch permits the fan to operate only when additional air flow is required to reduce radiator coolant temperatures . During periods of operation, when radiator discharge air temperature is low, (be-low approximately 150°F), the fan clutch limits fan speed to 800-1,400 RPM. At this RPM, the clutch is disengaged since a 'small oil pump, driven by the separator plate, forces the silicone oil into the reservoir between the separator plate and the front cover assembly. Also the passage from this cavity to the clutch area is closed by a sliding valve . (See Figure 7-16, Line A.) As operating conditions produce a high radiator discharge air temperature (above approximately 150°F), the temperature-sensitive bimetal coil tightens to move the sliding valve plate, allowing the flow of silicone oil into the clutch chamber to engage the clutch, providing maximum fan speed of approximately 2,200 RPM . (See Figure 7-16, Line B .) The clutch coil is calibrated so that with a road load at an ambient temperature of approximately 90°F, the clutch is at a point of shifting between high and low fan speeds . 7-1 4 SECTION 7B - ENGINE COOLING SYSTEM Figure 7-15- Engine Cooling Fans NOTE : The 2nd design was interim 1988 to 4-1-89. The 3rd design started 4-2-89. Part #15643265 stamped RL the clutch is engaged at all speeds to help reduce the radiator temperature and fan noise. It engages only the amount required to keep the radiator within the operating temperature. PASSENGER CARS, LIGHT-DUTY TRUCK AND MOTOR HOMES I/ . 4500 4000 3500 0 3000 a 2500 ONE MEN z 2000 Q 1500 . . BNNE Z PP_ Fu r 0 O 1000 2000 3000 4000 INPUT SPEED = N' / 4 ME, 1000 500 / N' = Nf (FAN SPEED WITHOUT FAN DRIVE) 5000 Figure 7-1 6- Typical Speed and TemperatureModulations ENGAGED o I IW y lw I I I f w z W ll! la AN SPEED I~ I I SECTION 7B - ENGINE COOLING SYSTEM No attempt should be made to adjust the calibration of the engine fan clutch assembly as each assembly is individually calibrated at the time of manufacture . In extreme high temperature for rescue and multi-stop delivery vehicles or winter snowplow applications where the snow blade interferes with air flow, disconnecting the fan clutch thermostat control increases air flow through the radiator by allowing the fan speed to more closely follow engine speed until approximately 2,000 RPM. To disconnect the bimetal coil spring thermostat on Eaton and Delco types, move the spring end tab out of the retaining slot and position counterclockwise (Figure 7-17) . Figure 7-17-Spring End.Tab CAUTION : DO NOT REMOVE THE SPRING COMPLETELY . COMPLETE REMOVAL OF THE SPRING CAN CAUSE THE FAN TO "FREE WHEEL" AND CAUSE OVERHEATING . NOTE: The heater hose routing should not be altered from the standard system . If an auxiliary heater is added, it should be routed similarly to the RPO (C36) rear heater . Where the heater water return is routed to the radiator outlet tank, a shut-off valve should not be placed in the heater circuit . A nipple has been provided in the radiator outlet tank for heater return water (Figure 7-18) . The temporary rubber shipping cap should be removed, and the heater return (suction) hose should be attached to the radiator nipple using the clamp supplied with the shipping cap. Figure 7-18 - Radiator Outlet Tank - Heater Return Water RADIATOR/HEATER AND ENGINE DEAERATION SYSTEM (After 1983 Model) Heavy-duty cooling equipment is required when air conditioning or auxiliary belt-driven equipment is 'installed. Continuous coolant flow is necessary from the heater connection on the engine to the heater connection on the radiator to control oil temperatures during closed thermostat (warm-up) operation . Shutting off this flow may result in premature engine or transmission failure . If a heater unit is not installed in the vehicle or a heater shut-off valve is required, a line connecting the heater connection on the engine to the heater connection on the radiator must be installed . When a shut-off valve is required in the heating system, it must be "tee'd" into the system in such a manner as to maintain a continuous flow between the engine heater connection and the radiator heater connection at all times . Figure 7-19-6.2L Diesel Engine Hot Water Flow 7-1 6 SECTION 78 ENGINE COOLING SYSTEM The 454 CID gasoline engine is essentially-the same as the 6.21- diesel engine shown in Figure 7-19 except that hot water comes from the thermostat housing . Hot water enters the bottom of the heater core and exits out the top for better heat dissipation . The coolant level should be at the "Full Cold" mark when the system is cool or at ambient temperature . After the vehicle has been driven sufficiently to obtain normal operating temperatures, the level should be above the "Full Cold" mark. MAINTENANCE AND INSPECTION Periodically, the radiator cap should be removed to observe coolant level in the radiator . The coolant level, appearance and strength should be checked periodically . It should be drained and replaced at the intervals recommended in the Maintenance Schedule, or sooner if it is dirty. Hoses should be checked regularly for signs of damage or deterioration and hose clamps tightened if necessary. Check hoses for cuts or abrasion damage . If the hoses have become hard and brittle and show signs of cracking as a result of engine heat, they should be replaced . Hoses should also be replaced if they are soft and spongy, or swollen as a result of exposure to oil and grease. Any flaking or deterioration of the inner lining of the hose is also reason for replacement. Such particles can clog the cooling system, reducing its efficiency. The radiator cap should be washed with clean water and pressure checked every 12 months . COOLANT LEVEL The need for additional coolant can be detected by observing the level of coolant in the "see through" reservoir while the engine is at normal operating temperature . The radiator cap need not normally be removed . (See Figure 7-20.) CAUTION : TO HELP AVOID THE DANGER OF BEING BURNED, DO N,PT REMOVE THE RADIATOR CAP WHILE THE ENGINE AND RADIATOR ARE STILL HOT. SCALDING FLUID AND STEAM CAN BE BLOWN OUT UNDER PRESSURE IF THE CAP IS TAKEN OFF TOO SOON . Coolant levels in any radiators with coolant recovery bottles should be maintained to the top of the filler neck. The recovery bottle should be at its appropriate mark when checking . Regardless of whether freezing temperatures are expected or not, cooling system protection should be maintained at least to -34°F, to provide adequate corrosion protection and loss of coolant from boiling . When adding solution due to a loss of coolant for any reason or in areas where temperatures lower than -34°F may occur, a sufficient amount of an ethylene glycol based antifreeze that meets GM specification 1825-M should be used (GM Part No. 1052753 - Gallon or equivalent) . Figure 7-20 - Coolant Recovery Bottle 7- 1 7 SECTION 713 ENGINE COOLING SYSTEM Antifreeze with a glycol content less than required for -34°F protection, also has a boiling point that is less than the temperature indicating light setting . The chart shown in Figure 7-21 shows the boiling point of water and of glycol in relation to pressure, and as CONCENTRATED ANTIFREEZE IS FLAMMABLE the chart shown in Figure 7-22 shows the relationship of the freeze point/flash point of antifreeze at various percentages by volume of solution . Understanding this potential fire source requires studying the chart of Figure 7-21 in relation to the information presented in Figure 7-22. It should be noted that an antifreeze related fire is the result of sustained driving while the vehicle is in an "overheat condition" indicated by a full scale reading of the temperature gage and/or steam from under the hood. These fires appear after catastrophic engine damage has occurred. PRESSURE (LBS ./SQ. IN.) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 33% by Volume Solution 40% by Volume Solution 50% by Volume Solution 60% by Volume Solution 68% by Volume Solution (Maximum Freezing Protection) Concentrated BOILING POINT (°F) WATER GLYCOL MIX (5A/50) 212 215 .3 218 .5 221 .6 224 .6 227 .4 229 .8 232 .8 234 .8 237 .1 239 .4 241 .6 243 .7 245 .7 247 .8 249 .7 251 .7 253 .6 223 .5 227 .2 230 .0 233 .0 236 .0 238 .8 241 .6 244 .0 246 .2 249 .2 251 .7 254 .5 256 .3 258 .3 260 .3 262 .5 264 .4 266 .2 TEMPERATURE FREEZE BOIL'` 0°F -12°F -34°F - 63°F -90°F 220°F 222°F 227°F 232°F 241°F -8°F 320°F Flash Point (Cleveland Open Cup) 68% by Volume Solution Concentrated None 257°F Fire Point (Cleveland Open Cup) 68% by Volume Solution Concentrated None 266°F * At sea level atmospheric pressure. The boiling point decreases about 2 degrees Fahrenheit per 1,000 feet of altitude and increases about 2.5 degrees Fahrenheit per pound of pressure developed in the system . Figure 7-22 - Coolant Freeze Point/Flash Point " Alcohol- or methanol-based antifreeze, or plain water, are not recommended for your engine at any time. They will not provide proper protection against corrosion . " Additives in addition to a good quality ethylene glycol based antifreeze meeting the GM specifications are not required or recommended . Many of the claims for additives are associated with better heat transfer or cooling, but these claims are not supported by test data. In some instances, the ingredients may be incompatible with the recommended coolant . Also, when used alone with water as is sometimes suggested, the additive may not provide the corrosion protection given by the recommended coolant solution . Figure 7-21 - Boiling Point vs. Pressure Chart Water/Glycol NOTES : FREEZING POINT & BOILING POINT Factory-installed temperature gages have been calibrated so the owner sees a mid-range reading as the "normal" operating temperature . The reason for this is that many owners tend to perceive 212°F as the boiling point. However, this is not the case in an engine with a 15-lb. pressure system and a 50/50 solution of glycol and water, as shown in Figure 7-21 . If the engine is equipped with a master gage or with one of the various digital electronic gages installed by RV manufacturers, the temperature reading of the engine will be higher than that of the factory-installed system . No matter which gage system is utilized, the motor home owner must realize that the purpose of any gage is to provide a warning of any rapid change in temperature from the "normal" reading of that particular gage. THERMOSTAT CHECK If the thermostat is suspected of not operating properly, it can be removed and tested as follows : 1 . Disconnect the battery negative cable at the battery . 2. Drain the cooling system until the radiator coolant level is below the thermostat. 3. Remove the coolant outlet attaching bolts and remove the outlet and thermostat. 4. Hang the thermostat on a hook in a minimum of 33% glycol solution at 25 degrees above the temperature stamped on the thermostat valve. Submerge the valve 7- 1 8 SECTION 7B ENGINE COOLING SYSTEM completely and agitate the solution thoroughly . Under this condition, the valve should open . 5. Remove the thermostat and place it in a 33% glycol solution that is 10 degrees below the temperature indicated on the valve . With the valve completely submerged and the solution agitated thoroughly, the valve should close completely . 4. Connect the battery negative cable . 5. Fill the cooling system with an ethylene glycol antifreeze 'and water mixture of 50/50. 6. Start and run the engine with radiator cap removed until the radiator upper hose becomes hot (thermostat open) . If the thermostat tests O.K., it can be reinstalled . If not, it should be replaced. 7. With the engine idling, add coolant to the radiator until the level reaches the bottom of the filler neck. Prior to installing the thermostat, make sure the thermostat housing and coolant outlet sealing surfaces are clean. 8. Install the cap, making sure arrows line up with the overflow tube. 1 . Place a 1/8-inch bead of RTV sealer (GM Part No. 1052366 or-equivalent) all around the coolant outlet sealing surface on the thermostat housing . 2. Place the thermostat in the housing . 3. Install the coolant outlet while the RTV sealant is still wet. Torque the retaining bolts to 20 ft. lbs. FLUSHING COOLING SYSTEM Various methods and equipment may be used to perform this service . If special equipment such as a back flusher is used, equipment manufacturer's instructions- should be followed. However, it is advisable to remove the thermostat before flushing the system . APPENDIX 7.2 RADIATOR ADDITIVES The following information has been extracted from GM Research Laboratories investigations concerning radiator additives for the prevention of overheating in the engine cooling system . The information is provided as an aid to the motor home owner in understanding the effects of using radiator additives . The object of the investigation was to review the use of radiator additives that are being marketed with the claim that they improve heat transfer and reduce the coolant temperature in the engine cooling system . Conclusions were: 1 . These radiator additives are composed principally of either water, ethylene glycol, or a combination of the two, and inhibitors such as those commonly used in antifreezes . Some additives contain oil and/or a surface active agent . 2. Tests with these additives fail to show any added benefit in heat transfer or reduction in coolant temperatures . 3. When these additives are used with water alone, they will probably provide less corrosion protection than an antifreeze used at the recommended concentration ; when used with conventional water-glycol solutions, the additive inhibitors may not be compatible with those from the glycol antifreeze. 4. Engine damage may result from loss of coolant due to overheating if the vehicle owner follows the recommendation to use these additives with water alone. (The boiling point of water is below the temperature at which the warning light is activated and the driver may not receive warning of a boiling condition .) 5. It is recommended that a strong position be taken against the use of these additives . There has been a proliferation of additive products on the market that are purported to increase the cooling capability of the cooling system . These products are usually sold in one-quart containers at a price ranging between $2.00 and $3.50 . Although a number of claims are made for these products, such as added corrosion protection, the removal ofscale, and pump lubrication, the principal claim is that associated with improved cooling . The major portion of these additives is either water, ethylene glycol, or a mixture of the two. Inhibitors have been added that are typical of those commonly used in antifreeze or in summer inhibitor additives . Some of the inhibitors in the additives may be incompatible with inhibitors in antifreeze solutions ; for example chromates are often incompatible with ethylene glycol antifreeze. If the additives are used with water alone, the inhibitors may not provide sufficient protection to all metals, and in some cases they may cause excessive corrosion ; for example, amine inhibitors are aggressive to copper alloys and nitrite attacks solder unless other inhibitors are present to compensate for these effects. The one variant in some cases is the use of a surface active agent that may increase heat transfer at a metal surface . One laboratory has shown increased heat transfer under controlled laboratory conditions but not in automotive service . However, surface active agents are often unstable at high temperatures, and they would not be expected to endure for long . The disadvantage of the surface active agent, as well as oil, is its tendency to cause increased foaming in the cooling system . Most of the claims are associated with better heat transfer or cooling, but these claims are not supported by testdata. Since the bulk of the material is water or ethylene glycol, it should not be expected that the addition of these additives would prevent overheating or make the engine run any cooler than when a quart of water or antifreeze had been added . It is possible that, in practice, the addition of a quart of this material may restore the coolant to the proper level, which provides better cooling, but so would the addition of water or ethylene glycol antifreeze. The claim that these additives provide better heat transfer when added to water alone, is apparently based on the fact that they contain inhibitors that prevent the formation of corrosion products that would impair heat transfer . However, the suggestion that they can be used with water alone may offer a problem . First, the concentration of inhibitors may be less than that normally provided by a good antifreeze at the minimum recommended concentration of 33-1/3 percent and second, the inhibitors may not be as effective in preventing corrosion as those in a well-formulated antifreeze . Furthermore, the boiling point of water is 12 degrees lower than that of a 44 percent ethylene glycol solution (262°F vs. 250°F at 15 PSIG), and this may lead to loss of coolant and damage to the engine because the warning light is set to come on at higher temperature than that of the boiling point of water. APPENDIX 7-3 ENGINE COOLING INSTRUCTIONS TO RV MANUFACTURERS The following information is provided as an aid to the motor homeowner in understanding the essentials of the engine cooling requirements as provided to major RV manufacturers . All chassis manufacturers (Chevrolet/ GMC, John Deere/Ford, Dodge) furnish the various RV manufacturers with Body Builders Books which provide basic instructions for the correct building procedures on an individual chassis . Essential engine cooling requirements are : 1 . All chassis manufacturers require a minimum grille opening stated in square inches to provide sufficient air to cool the manufacturer's engine . The instructions also indicate the grille to be a minimum of four inches from the radiator core. Listed below are the minimum frontal areas for the major manufacturers . Chevrolet/GMC . . John Deere/Ford 1976 Dodge . . . . . . 1979 Dodge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .360 .530 . 367 . 430 square square square square inches inches inches inches Dodge and John Deere specify a maximum 45-degree air entry angle . 2 . Large objects should not be placed in front of the radiator core or grille such as batteries, spare tires, washer bottles, coolant overflow tanks, bicycles, etc., as these types of items restrict air flow to the radiator core . 3. The grille opening should be "open" in configuration . Small holes for the grille opening tend to restrict air flow more than large holes although both may have the same frontal area. 4. Cooling can be improved by inserting filler panels between the outer vertical side edges of the radiator and grille. In addition, a filler panel should be fitted horizontally from the bottom of the radiator out to the bottom of the grille . This will prevent air from by-passing the radiator and exiting through the front wheel house area or under the radiator . These panels will force the air through the radiator . 5. A flexible air-tight seal must be provided between the upper radiator support and the body to aid idle cooling and prevent hot air recirculation. The seal assures that incoming "ram air" must go through the radiator core rather than by passing the radiator core (going up and over the core) . 6. Bug screens should be avoided if at all possible. If conditions require a bug screen, motor home owners are advised to be alert to possible engine overheating problems as well as temperature changes . The screen's mesh should be - at most - half as dense as that of standard household screening . Household screening will create an overheating condition . The bug screen should be removed immediately upon leaving the bug infested area. SECTION 7C , GASOLINE ENGINE Fuel Types ENGINE FUELS ENGINE FUELS Unleaded Gasoline - (In GM Vehicles Designed for Leaded Fuels) The need for leaded gasoline in the U.S. is decreasing as older vehicles designed for leaded gasoline are replaced with new ones requiring unleaded gasoline. Furthermore, the U.S. Environmental Protection Agency (EPA) began phasing down the concentration of lead in leaded gasoline during July, 1985 . These two facts taken together could result in limited supplies of leaded gasoline being available for vehicles designed for such fuel . The lead phasedown was based on health considerations and a desire to eliminate fuel-switching - the practice of using leaded gasoline in vehicles equipped with catalytic converters . Due to the fact that lead destroys the emission control properties of catalysts, leaded gasoline should not be used in engines equipped with these devices . GM supports this EPA effort to reduce lead emissions and to reduce fuel-switching . All GM gasoline-fueled engines in (1 .) passenger cars starting in 1971, (2.) 1971-78 trucks less than 6,000 lbs. GVW, and (3.) rucks less than 8,500 lbs. GVW starting in 1979, were designed to use unleaded gasoline and are unaffected by lead reduction efforts . and loads. However, if excessive valve seat wear does occur, cylinder heads may be rebuilt with hardened valve seat inserts to avoid recurrence of the problem . For those engines designed for leaded gasoline, GM recommends that they continue to be fueled with leaded gasoline as long as such gasoline is available . Lead Substitute Additives - GM has not issued a service bulletin recommending the use of any lead substitute additive by the individual customer . GM has taken the position that many additives on the market today do not have sufficient data and testing to factually back up some of the claims being made . Some additives may in fact actually be counterproductive to the government's reasoning for lead removal and create undesirable emissions problems as well as being detrimental to overall engine life . There is a consensus among fuel and lube engineers that the use of lead substitute additives should not be a consumer decision and that if the need for an additive becomes established, the product should be blended into the gasoline as the fuel is produced by the the gasoline supplier to ensure better chemistry control . Gasohol - Gasohol, a mixture of 10 percent ethanol (grain alcohol) and 90 percent gasoline may be used in Chevrolet gasoline engines without voiding the warranty . However, because of the composition of gasohol, engines will tend to operate leaner with gasohol than with gasoline. For all GM gasoline-fueled engines in (1 .) pre-1971 pas- This can result in drivability conditions usually associated senger cars and trucks, (2.) 1971-78 trucks over 6,000 with leaner mixtures. Also the increased volatility of lbs. GVW, and (3.) trucks over 8,500 lbs . GVW starting gasohol can contribute to hot weather drivability problems in 1979, concerns exist about engine knock and exhaust if adjustments are not made to the gasoline blend during valve seat durability when such engines are operated on the refining process . gasoline without lead . The higher octane rating of gasohol compared to most The octane quality of leaded regular gasoline is generally unleaded gasolines, could help" reduce the tendency for higher compared to unleaded regular gasoline . Thus, spark knock. But, gasohol contains less energy than gasswitching from leaded regular to unleaded regular in ve- oline, and fuel economy may or may not be quite as good. hicles designed for leaded regular may cause some en- However, in some instances, depending on the entire degines to knock. Occasional light knock is of little concern. sign and calibrations, and certain operating conditions, it However, persistent, heavy knock can cause engine dam- is possible to get improved fuel economy . age and should be avoided . Two alternatives are available to avoid knock. The first is to use unleaded premium gas- Exhaust emission levels may change up or down with the oline (or a mixture of unleaded regular and unleaded pre- use of gasohol, again, depending on the calibration of the mium) . The other is to retard the engine's basic spark engine . At the present time, however, the EPA has not restricted the use of gasohol . timing. The lead in gasoline creates a "cushion" between the valve and valve seat to minimize wear. Valve seat wear is aggravated by operating at high engine speeds and loads, particularly for long periods of time . Engines designed to use unleaded gasoline have hardened valve seats to compensate for the removal of lead. Engines designed to use leaded gasoline can avoid excessive wear if operation is limited to reasonable speeds If gasohol is spilled on a painted surface, some dulling or softening of the paint may result. NOTE: Refer to the information contained in Appendix 7-4 and Appendix 7-5 at the end of this section of the manual concerning the use of gasohol in vehicles equipped with gasoline engines, and potential problems of using methanol/gasoline blends . 7-22 SECTION 7C - ENGINE FUELS DIESEL ENGINE Fuel Types NOTE : Do not use starting fluids . Such aids can cause immediate engine damage . Diesel fuel is available in No. 1 or No. 2 grades. The difference between the grades is that No . 1 diesel fuel has had much of the paraffin (wax) removed . While the wax content increases the amount of energy in the fuel, it can clog the fuel filter(s) in cold weather, and stop the flow of fuel to the engine . The Cetane Number used in rating diesel fuels is an indication of the energy content of the fuel - the higher the Cetane Number, the higher the energy content . The higher Cetane rating will improve the cold-starting performance of the engine, as long as the higher wax content does not impede the flow of fuel through the system . This introduces two other factors which affect diesel fuel Cloud Point and Pour Point. The Cloud Point represents the temperature at which a predetermined percentage of the wax content in the fuel solidifies . The Pour Point represents a lower temperature at which the fuel cannot be made to flow. The moisture content of the fuel can also affect cold weather starting and performance . Water can separate out of the fuel, settling in low points of the fuel line and freezing, or forming minute ice particles which flow into the filter(s) and tend to clog the filter(s) . Additives can be used to lower the Pour Point of the fuel, and to prevent moisture freezing in the fuel. However$ additives will have little effect on the Cloud Point . Mixing different grades of diesel fuel can also be used to change the Pour Point and to change the Cloud Point as well. APPENDIX 7.4 USE OF GASOHOL IN GASOLINE ENGINES The following information was extracted from a Chevrolet Dealer Service Information Bulletin relating to the use of gasohol in vehicles equipped with gasoline engines . Reference : Chevrolet Dealer Service Information Bulletin No. 80-1-3 (July, 1979) Gasohol, a fuel generally composed of 10 percent ethanol (grain alcohol) and 90 percent gasoline, is receiving considerable attention as a fuel for gasoline engines. It is possible that other kinds of alcohol, such as methanol (wood alcohol) may be added to gasoline in the future ; however, this bulletin deals only with gasohol containing up to 10 percent ethanol . (Gasohol containing methanol is not being marketed at this time.) The purpose of this bulletin is to provide information which may be helpful in answering questions about gasohol which may arise regarding : " " " " " " Availability Drivability Fuel Economy Service Adjustments Warranty Coverage Emission Levels Availability Gasohol currently is available at many retail stations in the Midwest and some retail stations on the East Coast . Nationwide availability is expected to increase . Drivability Due to the composition of gasohol, vehicles equipped with gasoline engines will operate leaner with gasohol than with gasoline . This leaner operation with gasohol may tend to cause drivability conditions usually associated with leaner mixtures . However, drivability of vehicles with Computer Controlled Catalytic Converter (C-4) or Closed Loop Catalytic Converter (CLCC) Systems probably will be affected less, because these systems compensate for the leaning effect of gasohol. NOTE: (Provided as a reference for the motor home owner .) If your vehicle is several years old, you should plan on changing all of the fuel filters at least once and the carburetor filter more than once. The reason given for this is that alcohol in itself is a solvent which dissolves the deposits left by gasoline in the fuel system . The increased volatility of gasohol also can contribute to hot-weather drivability problems if, during the refining process, adjustments are not made to the gasoline blend . In general, gasohol has a higher octane rating than most unleaded gasolines, and it could help reduce the tendency for spark knock. Fuel Economy Gasohol (10 percent ethanol, 90 percent gasoline) contains less energy than gasoline by itself . Consequently, fuel economy of gasohol may not be quite as good as gasoline. However, there are differences in engine design and calibration which make it possible in some instances to achieve better fuel economy with gasohol . Service Adjustments Specified engine settings must not be changed for gasohol use . The service specifications for which the vehicle has been certified must be maintained. Warranty Coverage The use of gasohol containing up to 10 percent ethanol will not void the vehicle warranty. Dealers are requested to inform their Area Service Manager of any fuel system failures which are believed to be related to gasohol use . If gasohol contacts a painted surface, it may cause dulling or softening of the paint. Dulling or softening of paint due to contact with gasohol is not covered under the vehicle warranty. Any drivability condition which is related solely to gasohol use is not covered under the vehicle warranty. Emission Levels Some changes in vehicle exhaust emission levels may occur when using gasohol. For example, carbon monoxide (CO) emissions will decrease in most vehicles, due to leaner mixture, but hydrocarbons (HC) and oxides of nitrogen (NO x) emissions may either decrease or increase, depending on how the engine is calibrated . Exhaust emission levels of vehicles equipped with C-4 or CLCC systems should be affected less than vehicles without these systems . The generally higher volatility of gasohol compared to gasoline may result in increased evaporative emissions . At the present time, the Environmental Protection Agency is not restricting the use of gasohol . However, local or state regulations, if applicable, must be observed . APPENDIX 7-5 METHANOL/GAPOSE SOLINE BLENDS POTENTIAL PROBLEMS The following information has been extracted from a GMC Newsletter and is provided as an aid to the motor home owner concerning the potential problems posed by methanol/gasoline blends . Reference : GMC Truck & Bus Group Newsletter (January, 1984) USE OF GASOLINE/ALCOHOL BLENDS EXPLAINED IN OWNER'S MANUALS Owners of 1984 model GM automobiles are given specific information in their owner's manuals on what types of fuel may be used in their vehicles . On the subject of gasoline/alcohol blends, the manuals state : Gasoline/Ethanol Blends Blends of unleaded gasoline and ethanol (grain alcohol), sometimes known as gasohol, are available in some areas . You may use these blends in your car, if they are not more than 10 percent ethanol, without jeopardizing the New Vehicle and Emission Warranties . Be sure the gasoline/ethanol blend has octane ratings no lower than those recommended for unleaded gasoline . Most drivers will not notice operating differences with blends of up to 10 percent ethanol, but some may. In that case, your dealer can make certain adjustments, provided they do not violate the Federal Emissions Standards . If you are still not satisfied with ethanol-gasoline blend performance, you may prefer to use unleaded gasoline . Other Gasoline/Alcohol Blends Some fuel suppliers sell gasoline containing alcohol without advertising the presence of alcohol or giving it a special name such as gasohol . If you are not sure whether there is alcohol in the gasoline you buy, check with the service station operator . DO NOT USE gasolines containing methanol (methyl or wood alcohol) that do not also contain cosolvents and corrosion inhibitors for methanol. Also, DO NOT USE gasolines that contain more than five percent methanol even if they contain cosolvents and corrosion inhibitors. Fuel system damage or vehicle performance problems resulting from the use of such fuels are not the responsibility of General Motors and may not be covered under the new vehicle warranties . Although gasolines containing five percent or less methanol and appropriate cosolvents and inhibitors for methanol may be suitable for use in your car, evidence of their suitability is as yet incomplete ; therefore GM cannot, at this time, endorse their use. METHANOL/GASOLINE BLENDS POSE POTENTIAL PROBLEMS Gasoline quality is an important factor in providing satisfactory engine and vehicle performance and fuel system life . Gasoline has traditionally been composed entirely of a mixture of hydrocarbons and its quality generally has been sufficient to prevent problems with vehicle performance and fuel system materials . In recent years, howevet, the quality of some gasolines has changed . Economic and other factors have led suppliers to use alcohols as gasoline components . The first of these was ethanol (grain alcohol), which was popularized in gasoline under the name "Gasohol." Vehicle performance and fuel system durability with gasolines containing up to 10 percent ethanol, by volume, have generally been satisfactory . More recently, methanol (wood alcohol), an alcohol with distinctly different properties than ethanol, has become a gasoline blending agent. The,addition of methanol to gasoline for use in motor vehicles is receiving increased attention due to favorable economics, excess methanol production capacity, and the desire to reduce petroleum imports . General Motors recognizes the favorable aspects of pure methanol as a future alternative fuel and certainly will produce cars that can use methanol if it becomes generally available . However, current use of methanol in gasoline can pose problems if used in today's cars over an extended period - even at low methanol concentrations in gasoline . GM is concerned about the rapid increase in the use of methanol/gasoline blends in today's cars for two reasons : " There is no hard evidence on how much methanol can be blended with gasoline without adversely affecting vehicle operation and durability . " There is no adequate service station pump labeling system that will tell motorists the methanol content of the fuel they are purchasing. There is limited information that suggests small amounts (up to five percent) of methanol in gasoline may be suitable if a cosolvent- an ingredient that prevents the gasoline and methanol from separating when trace amounts of water are in the fuel - and a corrosion inhibitor to prevent damage to fuel system components are used. Evidence on the suitability of such blended fuels is incomplete and, therefore, their use cannot be endorsed by GM at this time. 7-25 APPENDIX 7-5 METHANOL/GAS'LOLINE BLENDS POSE POTENTIAL PROBLEMS (Cont1d) It is likely some engines and fuel systems will be sensitive to methanol/gasoline blends that contain higher concentrations (greater than 10 percent) of methanol - even if the fuels contain cosolvents and corrosion inhibitors. This sensitivity is generally related to compatibility with materials commonly used in vehicle fuel systems, such as fuel tank plating and certain rubber parts in carburetion systems. Also, drivability - performance of the vehicle - is adversely affected . Historical Perspective Alcohol/gasoline mixtures have been studied for more than 50 years. In the 1960s and early 1970s, the use of these blends was proposed (not always appropriately) as a way to reduce vehicle exhaust emissions and improve fuel economy . However, because the cost of alcohol was significantly higher than that of gasoline, the widespread use of alcohol/gasoline blends was not economically feasible. GM is continuing to evaluate methanol/gasoline blends in both laboratory and vehicle tests to determine the effects of the blends on fuel system materials, engine deposits, drivability, emissions and fuel economy . Two significant actions of the past decade have renewed and expanded interest in alcohol/gasoline blends . There are economic advantages that encourage blending methanol with gasoline. The average national tank price for unleaded gasoline sold to service station dealers (excluding taxes) in August, 1984 was approximately 94 cents a gallon, while methanol's cost was between 45 and 49 cents a gallon . On the other hand, ethanol's cost was between $1 .62 and $1 .80 per gallon . Ethanol/gasoline blends are competitive with gasoline only if a tax subsidy is allowed, but methanol/gasoline blends are not only competitive, they are enticing for the refiner, blender and retailer. The U.S. Environmental Protection Agency (EPA) has granted waivers, legally allowing the blending of methanol in gasoline . Waivers cover methanol concentrations as high as 12 percent, as long as cosolvents are used . GM and other auto companies have not agreed with the EPA's decisions granting waivers for methanol/gasoline blends . The concern over use of methanol/gasoline blends has been heightened because illegally high levels of methanol have been found in some gasolines . An EPA probe that began in the spring of 1983 in the Detroit area, revealed illegally high levels of methanol in gasoline . Out of 250 samples of unleaded gasoline from about 150 service stations, about eight percent - or 20 samples - had levels of methanol above those allowed by waivers, or did not contain cosolvents . Because of concern over the compatibility of methanol/ gasoline blends with current vehicle engines and fuel systems, and illegal blending of methanol in gasoline, a number of states are planning to require that the methanol content of the fuel be posted on dispensing pumps. Although this is a step in the right direction, GM believes that motorists would be better served by a uniform labeling system nationwide . This would eliminate confusion caused by states adopting different labels . First, the severe interruptions of petroleum imports emphasized the need to increase production of domestic energy sources and reduce dependence on imported oil. The production of alcohol fuels, particularly ethanol, became politically attractive in the late 70s at the height of the energy crisis . Its use was encouraged through tax subsidies . Commonly sold as Gasohol, it is now also marketed as unleaded, super unleaded, or premium unleaded gasoline (depending on its octane level), marked "with ethanol ." Also, during the recent recession, capacity for production of methanol from natural gas far exceeded demand . Methanol thus assumed a new attraction as a gasoline blending agent. The outlook for use of pure methanol as an automotive fuel is positive because the technical knowledge necessary to design and build methanol-fueled engines and vehicles is rapidly developing . (See Figure A7-5-1 .) In blends with gasoline, as stated earlier, methanol may not be suitable for use in either existing vehicles or future model year vehicles unless the vehicles are modified . NOTE: Several trade publications have predicted a sharp increase in the amount of methanol used as automotive fuel by the end of the decade . The "Lundberg Letter" projects methanol fuel use in 1990 will be 40 times greater than in 1980. The second action which increased interest in alcohols as fuels was the reduction in the amount of lead antiknock additives used in gasoline . This reduction spurred by the EPA, occurred for two reasons: " The need for unleaded gasoline in cars equipped with catalytic converters. " The need to limit the emissions of lead into the atmosphere (by lowering permissible lead concentrations in leaded fuel). 7-26 APPENDIX 7-5 METHANOL/GASOLINE BLENDS POSE POTENTIAL PROBLEMS (Cont'd) " DRIVABILITY . Drivability is generally worse with methanol/gasoline blends than with gasoline alone . In hot weather, the generally high volatility of the blends, compared with gasoline, causes a greater tendency toward vapor lock problems. Cold weather problems stalling and hesitation - have been reported. " SEPARATION . The presence of even trace amounts of water in the fuel system may cause methanol/gasoline blends to become cloudy and separate into two layers, a gasoline layer on top and an alcohol/water layer on the bottom . A vehicle will not run satisfactorily on the alcohol/water mixture and corrosion of fuel system parts and deterioration of rubber parts can be greatly accelerated by contact with this mixture . Water tolerance of blends is increased by cosolvents, but even these do not completely eliminate the separation problem. " FUEL ECONOMY . In late-model cars, fuel economy (miles per gallon) generally decreases with the addition of methanol to gasoline. This is due to the lower energy content (per gallon) of methanol compared with gasoline. For example, a blend of 10 percent methanol in gasoline contains about five percent less energy per gallon than gasoline . Figure A7-5-1- U.S. Fuel Methanol Forecast Alcohols offer a means of replacing some of the octane (antiknock) quality previously provided by lead compounds . Major Disadvantages - of Methanol/Gasoline Blends There are a number of disadvantages associated with the use of methanol/gasoline blends in vehicles designed for gasoline . Of major significance are : " DETERIORATION OF FUEL SYSTEM MATERIALS . Rubber, plastic, and metallic fuel system components in most vehicles were designed for use with gasoline, and may not provide satisfactory service with methanol/ gasoline blends . Although few long-term durability tests have been run with blends, the results from a number of laboratory evaluations, as well as problems reported by motorists, make it clear that a variety of problems can occur . Most material problems are a function of time rather than distance traveled, so a 50,000-mile test completed in one year may not indicate what would happen during 50,000 miles of operation over four or five years . Components possibly affected include fuel tanks, in-tank fuel pumps, carburetion and fuel injection systems, and nitrile rubber commonly used in vehicle fuel systems . " EVAPORATIVE EMISSIONS. Unless major changes are made in the distillation characteristics of gasoline, the addition of methanol to it significantly increases vapor pressure. This almost always results in a substantial increase in vehicle evaporative emissions . Regulatory Considerations The regulatory aspects of methanol/gasoline blends are complex . The Clean Air Act prohibits the addition of additives to unleaded fuel, including methanol, unless the fuel additive manufacturer obtains a waiver from the EPA . In order to obtain such a waiver, the fuel additive manufacturer must show that the fuel will not cause - or contribute to - the failure of the vehicle or engine to meet the applicable emission standards for five years, or 50,000 miles . The EPA has published guidelines that stress the need for development of data on possible methanol blending problems . GM supports the principles embodied in the guidelines, but believes it is important that the EPA give careful consideration to potential problems when reviewing any fuel additive waiver application for alcohol/ gasoline blends . During the last five years, a number of waivers have been granted . 7-27 APPENDIX 7-5 METHANOUGASOLINE BLENDS POSE POTENTIAL PROBLEMS (Cont'd) GM and other automobile manufacturers are concerned that some of the blends approved by the EPA may be detrimental to vehicle emissions, performance and components. Although several fuel suppliers have been successful in marketing methanol/gasoline blends, the long-term effects of the blends on vehicle durability are not yet known . To assure customer satisfaction with its vehicles, GM is establishing a system to track reported vehicle problems to determine if methanol/gasoline blends are responsible . If further investigation determines methanol/gasoline blends can be used in the existing fleet of vehicles without materials, drivability, or emissions problems, GM believes their use should be permitted . But only with adequate labeling of fuel at the pump will consumers be able to recognize the contents in the fuel they are purchasing . SECTION 7D - ENGINE FUEL SYSTEMS ENGINE FUEL SYSTEMS There are distinct differences between the gasoline and diesel engine fuel systems . The 5.7L and 7.4L (Mark IV) gasoline engines use a carburetor to mix fuel with air . Strong engine vacuum, drawing intake air through the carburetor venturis, causes fuel to flow from the carburetor ports to be mixed in the air stream turbulence . This air/ fuel mixture is distributed to each cylinder through the intake manifold. Engine speed is controlled by the position of throttle plates in the carburetor which open and close (by means of the accelerator linkage) to vary the amount of air/fuel mixture entering the manifold and cylinders . In the diesel engine, fuel is injected directly into a prechamber above each cylinder where it is mixed with air . Engine speed is controlled by varying the amount of fuel injected. neck, and a fuel gage sending unit. Its sole purpose is to provide a place for fuel storage . FUEL PUMP The fuel pump is located on the lower front half of the engine block on the passenger's side. Its purpose is to provide adequate pressure to move fuel to the carburetor. The fuel pump is a diaphragm-type pump and is actuated by the rocker arm through a link and a push rod . Some vehicles have a fuel pump with an outlet for a vapor return system . Any vapor which forms, is returned to the fuel tank along with hot fuel through a separate line. This greatly reduces any possibility of vapor lock by keeping cool fuel from the tank constantly circulating through the fuel pump. Some units are built with both mechanical and electric in tank pumps. The components used in each system, gasoline and diesel, will be described in separate sections . GASOLINE ENGINE SYSTEM DESCRIPTION EVAPORATIVE CONTROL SYSTEM The gasoline engine fuel system includes the fuel tank, fuel pump, fuel filter, carburetor and all fuel and vacuum lines. FUEL TANK The fuel tank is located behind the rear axle and is strapped to the frame. It includes the fuel filler cap and Light-duty and some heavy-duty vehicles are equipped with an emissions system designed to prevent escape of fuel vapor to the atmosphere (Figure 7-23) . Vapor generated by evaporation of fuel in the tank, previously exhausted to the atmosphere, is transferred by an emission line to .the engine compartment . During periods of inoperation, an activated. charcoal canister located in the emission line stores any vapor generated, for consumption during the next period of operation . VENT TO ATMOSPHERE (Above 10,000 Lbs . GVW - Federal) r _J --Z LT - 'I II I I L__J CHARCOAL_ CANISTER (Below 10,000 Lbs. GVW - Federal ; All GVW - California) AUXILIARY FEL TANK (If-so equipped- , - requires- additional charcoal canister with capacity for second tank.) venting L Figure 7-23 - Evaporative Control System TRANSFER VALVE (If So Equipped) MAIN FUEL TANK NOTE: 1985-1/2 thru 1989 HD5 Emissions - All models are vented to charcoal canister. 7-29 SECTION 7D ENGINE FUEL SYSTEMS The amount of vapor drawn into the engine at any time is too small to have any effect on fuel economy or engine operation . are placed in the inlet hole with the gasket surface outward. A spring holds the element outward, sealing it by compressing a gasket surface against the inlet fitting . With this closed system, it is extremely important that only vapors be transferred to the engine . To avoid the possibility of liquid fuel being drawn into the system, the following features are included as part of the total system : The carburetor inlet fuel filter should be replaced at the internals shown in the Maintenance Schedule . A plugged filter and/or check valve will restrict fuel flow. After assembling any filter element in the carburetor, always start the engine and check for leaks in the fuel line and fittings before installing the air cleaner .. 1 . A fuel tank overfill protector is provided on all series to assure adequate room for expansion of liquid fuel volume with temperature changes . (Fill is limited to 8090 percent total capacity.) For the P-Series, an additional fuel filter is located in the fuel line along the inside or outside of the right frame rail depending on the year built . It is replaced by disconnecting the fuel line on both sides of the filter assembly, removing the old assembly, installing a new one, and then reconnecting the fuel line. Use caution to avoid fuel spillage . 2. A one-point fuel tank venting system is provided on all series to assure that the tank will be vented under any conceivable vehicle attitude. 3. To protect the tank from mechanical damage in the event of excessive internal or external pressures resulting from the operation ofthis closed system, a pressure-vacuum relief valve, located in the gas cap, will control the tank's internal pressure. NOTE: The position of the filter(s) may vary on the P-Series with the installation of aftermarket fuel tanks. The installation of additional filters at each tank is not recommended, because of the added work load these restrictions would place on the mechanical fuel pump. System Hook-Up for Auxiliary Tank If an auxiliary fuel tank is to be added, it must be vented as shown in Figure 7-23. See Figure 7-24 for additional fuel tank considerations . A woven plastic filter is located on the lower end of the fuel pickup pipe in the fuel tank. This filter prevents dirt from entering the fuel line. Normally, no maintenance is required. Fuel stoppage at this point, indicates that the tank contains an abnormal amount of sediment; consequently, the tank should be removed and cleaned thoroughly . FUEL FILTERS An engine fuel filter is located in the carburetor fuel inlet . These fuel filter elements are of pleated paper. Elements RESTRICTED VENT .050 RETURN LINE ORIFICE IMPORTANT STORAGE VAPOR DOME ALLOWS NECESSARY ROOM FOR FUEL EXPANSION. POSITION OF SPIT BACK TUBE IN CONJUNCTION WITH LENGTH/POSITION OF FUEL FILL NECK CONTROLS FUEL FILL LEVEL TO APPROX . 80% A SPECIAL CAP DRAWS IN AT 2.0-2.4 INCHES OF VACUUM = 27-32 INCHES OF WATER COLUMN . THE CAP BLOWS OFF AT 2.2-2 .9 PSI = 60-80 INCHES OF WATER COLUMN. ELECTRICAL CONNECTION FOR FUEL GAGE AUX. POWER SHOULD NOT GO TO BOTTOM OF TANK TO ALLOW ENGINE RESTART TO GET OFF CAMP GROUND SUCTION PICK-UP W/SOME FORM OF SOCK FILTER FOR ROCKS AND BROOMSTRAWS ALL SHOULD HAVE RESTRICTED VENT TO PREVENT FUEL SIPHON WITH FUEL SLOSH AND DETER OVERFILL TYPICAL GM FUEL TANK TYPICAL SQUARE WELDED-UP---'O RV TANK SHOULD INCLUDE SAME FEATURES AS GM TANK Figure 7-24-Typical Fuel Tank Design Considerations 7-30 .055 060 RESTRICTOR DEPTH OF SPIT BACK TUBE CUrv i rsvw 80% TO 90% FILL SECTION 7D ENGINE FUEL SYSTEMS CARBURETOR oline engines . It features tamper-resistant controls to discourage readjustment of factory settings, which could affect either or both emission control and drivability . The carburetor is located on the top of the engine block, just under the air filter housing . Proper operation of the carburetor is extremely important as it performs several necessary functions . First, it controls the amount of air drawn in by the engine and controls the amount of fuel that is combined with air to form a combustible mixture . This must be done adequately to cover a wide range of operating speeds and conditions. Consequently the carburetor also controls engine output and speed by varying the amount of mixture reaching the eight cylinders . MAINTENANCE AND INSPECTION The system should be inspected and maintained in accordance with the Maintenance Schedule. Fuel lines should be checked for signs of leakage, damage or deterioration. Clamps must be tightened if they are loose . Filters in the fuel line and the evaporative control system should be replaced at the recommended intervals. The carburetor choke linkage should be checked and the mounting bolts tightened as recommended . Finally, the carburetor provides vacuum control for the spark advance and vacuum source for many of the federally mandated emission controls . CAUTION 1990 fuel injection requires only no lead fuel be used as regular fuel will ruin the catalytic converter. The M4MC model carburetor is used on most of the gasTBI INJECTOR TBI UNIT THROTTLE BODY PRESSURE REGULATOR FUEL RETURN LINE IN-LINE FUELFILTER FUEL PRESSURE LINE Figure 7-25 - TBI Fuel Supply System (Typical) GENERAL DESCRIPTION MODES OF OPERATION PURPOSE The fuel control system is controlled by an electronic control module . The ECM is the control center of the computer command control system and is located under the steering column support bracket . The basic function of the fuel control system is to control fuel delivery to the engine . Fuel is delivered to the engine by a throttle body injection (TBI) unit. The main control sensor is the oxygen (O~ sensor, which is located in the exhaust pipe. The OZ sensor tells the ECM the amount of oxygen in the exhaust gas, and the ECM changes the air/fuel ratio to the engine by controlling the fuel injector. A 14.7:1 air/fuel ratio is required for efficient catalytic converter operation. Because the constant measuring and adjusting of the air/fuel ratio, the fuel injection system is called a "Closed Loop" system (Figure 7-26). The ECM monitors voltages from several sensors to determine how much fuel to give the engine . The fuel is delivered under one of several conditions called ;.`modes ." All the modes are controlled by the ECM . Starting Mode When the key is first turned "ON," the ECM turns on the fuel pump relay for two seconds and the fuel pump builds up pressure to the TBI unit. The ECM checks the coolant temperature sensor, throttle position sensor (TPS), manifold absolute pressure map sensor, and crank signal, then determines the proper air/fuel ratio for starting . This ranges from 1 .5:1 at -36°C (-33°F) to 14.7:1, at 94°C (201°F) running temperature . The ECM controls the amount of fuel delivered in the starting mode by changing how long the injector is turned "ON" and "OFF." This is done by "pulsing" the injector for very short times. 7-31 SECTION 7D - ENGINE FUEL SYSTEMS different engines, and are stored in the programmable read only memory (PROM). When these conditions are met, the systems go into "Closed Loop" operation . In "Closed Loop," the ECM calculates the air/fuel ratio (injector on-time) based on the signal from the 02 sensor. This allows the air/fuel ratio to stay very close to 14 .7:1 . Acceleration Mode The ECM looks at rapid changes in throttle position and manifold pressure, and provides extra fuel . OTHER SENSOR INPUT INFORMATION Deceleration Mode ELECTRONIC CONTROL MODULE When deceleration occurs, the fuel remaining in the intake manifold' can cause excessive emissions and backfiring . Again, the ECM looks at changes in throttle position and manifold pressure and reduces the amount of fuel. When deceleration is very fast, the ECM can cut off fuel completely for short periods. 14 . 7 .1 COMMAND "CLOSED LOOP" 6S 2692-6E Figure 7-26 - "Closed Loop" TBI System Battery Voltage Correction Mode Clear Flood Mode When battery voltage is low, the ECM can compensate for a weak spark delivered by the distributor by : " Increasing injector on time of fuel delivered " Increasing the idle rpm " Increasing ignition dwell time If the engine floods, clear it by pushing the accelerator pedal down all the way. The ECM then pulses the injector at a 20:1 air/fuel ratio, and holds this injector rate as long as the throttle stays wide open, and the engine is below 600 rpm. If the throttle position becomes less than 80%, the ECM returns to the Starting mode. Fuel Cutoff Mode No fuel is delivered by the injectors when the ignition is "OFF." This prevents dieseling . Also, fuel is not delivered if no reference pulses are seen from the distributor, which means the engine is not running. Fuel cutoff also occurs at high engine rpm, to protect internal engine components from damage. Run Mode The Run mode has two conditions called "Open Loop" and "Closed Loop ." Open Loop When the engine is first started, and it is above 400 rpm, the system goes into "Open Loop" operation. In "Open Loop," the ECM ignores the signal from the 02 sensor, and calculates the air/fuel ratio based on inputs from the coolant temperature and MAP sensors. The system stays in "Open Loop" until the following conditions are met: 1 . The 02 sensor has varying voltage output, showing that it is hot enough to operate properly . (This depends on temperature.) 2. The coolant temperature sensor is above a specified temperature. 3. A specific amount of time has elapsed after starting the engine . The 7.4L engine is designed to operate "Open Loop" at idle . The system will go to "Closed Loop" when the rpm is increased and all conditions above are met. Closed Loop The specific values for the above conditions vary with FUEL CONTROL OPERATION The fuel control system (Figure 7-27) consists of the following components : " Throttle body injection (TBI) unit " Fuel pump " Fuel pump relay " Fuel tank " Accelerator control " Fuel lines " Fuel filters " Evaporative emission control system The fuel control system has an electric fuel pump, located in the fuel tank on the gage sending unit. It pumps fuel to the throttle body through the fuel supply line, then through an in-line fuel filter . The pump is designed to provide pressurized fuel at about 125 kPa (18 psi) . 7-32 SECTION 7D ENGINE FUEL SYSTEMS " Fuel meter body with: - Fuel injectors " Throttle body with: - Idle air control (IAC) valve - Throttle position sensor (TPS) Vacuum Ports a The throttle body portion of both TBI units may contain ports located above, or below the throttle valve. These ports generate the vacuum signals for the exhaust gas recirculation (EGR) valve, MAP sensor, and the canister purger purge system . FUEL PUMP AND SENDING UNIT FUEL SUPPLY LINE Fuel Injector(s) FUEL FILTER TBI UNIT FUEL RETURN LINE 4S 0055-6E Figure 7-27 - Fuel Control System A pressure regulator in the TBI keeps fuel available to the injectors at a constant pressure between 62 and 90 kPa (9 and 13 psi) . Fuel in excess of injector needs is returned to the fuel tank by a separate line . The ECM controls the injectors that are located in the fuel meter body assembly of the TBI. The injectors deliver fuel in one of several modes, described above . In order to properly control the fuel supply, the fuel pump is operated by the ECM through the fuel pump relay and oil pressure switch (see "Fuel Pump Electrical Circuit"). The fuel injectors (Figure 7-29) are solenoid-operated device, controlled by the ECM . The ECM turns on the solenoid, which lifts a normally closed ball valve off a seat. Fuel, under pressure, is injected in a conical spray pattern at the walls of the throttle body bore above the throttle valve. The fuel which is not used by the injectors passes through the pressure regulator before being returned to the fuel tank . Pressure Regulator The pressure regulator(see Figure 7-29) is a diaphragm- MODEL 220 TBI UNIT Model 220, (Figure 7-28), consists of three major casting assemblies : " Fuel meter cover with: - Pressure regulator a PRESSURE REGULATOR ® FUEL INJECTOR 13 FUEL INJECTOR INLET FILTER THROTTLE BODY ASSEMBLY FUEL FROM PUMP INJECTOR ELECTRICAL TERMINALS CONSTANT BLEED - (SOME MODELS) PRESSURE REGULATOR DIAPHRAGM ASSEMBLY PRESSURE REGULATOR SPRING 0 FUEL RETURN TO TANK G THROTTLE VALVE FUELINJECTORS 13 a THROTTLE BODY ASSEMBLY THROTTLE POSITION SENSOR (TPS) IDLE AIR . CONTROL (IAC) VALVE ASSEMBLY 5 FUEL METER BODY ASSEMBLY 6 FUEL METER COVER ASSEMBLY 8P 0922-AS Figure 7-28 - Model 220 TBI Unit 8P 0320-SY Figure 7-29 - TBI 220 Unit Operation 7-33 SECTION 7D ENGINE FUEL SYSTEMS passage + PCV + throttle valve + vacuum leaks) . Controlled idle speed is always specified for normal operating conditions. Normal operating condition is coolant temperature in operating range, the A/C is "OFF," automatic transmission in drive with proper Park/Neutral switch adjustment . A high or low coolant temperature, or A/C clutch engaged may signal the ECM to change the IAC counts . The minimum idle air rate inset at the factory with a stop screw . This setting allows enough air flow by the throttle valves to cause the IAC valve pintle to be positioned a calibrated number of steps (counts) from the seat during normal controlled idle operation. The IAC counts will be higher than normal on an engine with less than 500 miles, or an engine operating at high altitude or an engine with an accessory load such as the alternator, A/C, power steering or hydra-boost brakes activated . operated relief valve with injector pressure on one side and air cleaner pressure on the other. The function of the regulator is to maintain a constant pressure at the injectors at all times, by controlling the flow in the return line (by means of a calibrated bypass). The pressure regulator on a TBI 220 unit is serviced as part of the fuel meter cover and should not be disassembled . Idle Air Control System All engine idle speeds are controlled by the ECM through the idle air control (IAC) valve mounted on the throttle body (Figure 7-30) . The ECM sends voltage pulses to the IAC motor windings causing the IAC motor shaft and pintle to move "IN" or "OUT" a given distance (number of steps) for each pulse, (called counts) . 0 TERMINAL PINS 11 BALL BEARING ASSEMBLY STATOR ASSEMBLY ROTOR ASSEMBLY SPRING . PINTLE LEAD SCREW 0 FUEL METER COVER & BODY ASSEMBLIES Figure 7-31 - Idle Air Control (IAC) Valve (TBI 220) THROTTLE BODY ASSEMBLY IDLE AIR CONTROL VALVE ASSEMBLY A FILTERED AIR INLET B PINTLE THROTTLE VALVE D VACUUM PORTS - FOR ENGINE OR EMISSION CONTROLS 8P 0319-SY Throttle Position Sensor UPS) The throttle position sensor (TPS), is mounted on the side of the throttle body opposite the throttle lever assembly. Its function is to sense the current throttle valve position and relay that information to the ECM (see Figure 7-32). Throttle position information allows the ECM to generate the required injection control signals (base pulse). Figure 7-30 - Idle Air Control System (TBI 220 Unit) This movement controls airflow around the throttle plate, which in turn, controls engine idle speed, either cold or hot . IAC valve pintle position counts can be seen using a "Scan" tool. O counts corresponds to fully closed passage, while 140 counts or more (depending on the application) corresponds to full flow . " Actual or "controlled" idle speed is obtained by the ECM positioning the IAC valve pintle . Resulting idle speed is generated from the total idle air flow (IAC/ If the TPS senses a wide open throttle, a voltage signal indicating this condition is sent to the ECM. The ECM then increases the injector base pulse width, permitting increased fuel flow. As the throttle valve rotates in response to movement of the accelerator pedal, the throttle shaft transfers this rotation movement to the TPS. A potentiometer (variable resistor) within the TPS assembly changes its resistance (and voltage drop) in proportion to throttle movement . 7-34 SECTION 7D , ENGINE FUEL SYSTEMS By applying a reference voltage (5.0 volts) to the TIPS input, a varying voltage (reflecting throttle position) is available at the TPS output . For example, approximately 2.5 volts results from a 50% throttle valve opening (depending on TIPS calibration) . The voltage output from the TPS assembly is routed to the ECM for use in determining throttle position. When the engine is cranking or running, the ECM receives distributor reference pulses which in turn energize the fuel injectors. As a backup system to the fuel pump relay, the fuel pump can also be turned on by an oil pressure switch . When the engine oil pressure reaches about 28 kPa (4 psi), through cranking and the fuel pump relay does not complete the circuit, the oil pressure switch will close to complete the circuit to run the fuel pump. THROTTLE VALVE ENGINE CONTROL MODULE (ECM) THROTTLE POSiT10N SENSOR (TPS) AT An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The oil pressure switch will turn on the fuel pump as soon as oil pressure reaches about 28 kPa (4 psi). i e FUEL FILTER PART #25055052 A-C GF 481 In-line Filter - located inside RF from rail FUEL FILTER #25055052 GF481 Figure 7-32 - Throttle Position Sensor (17BI 220) FUEL PUMP CIRCUIT The fuel pump' is a turbine type, low pressure electric pump, mounted in the fuel tank . Fuel is pumped at a positive pressure (above 62 kPa or 9 psi) from the fuel pump through the in-line filter to the pressure regulator in the TBI unit (see Figure 7-25). Excess fuel is returned to the fuel tank through the fuel return line . The fuel pump is attached to the fuel gage sender assembly. A fuel strainer is attached to the fuel pump inlet line and prevents dirt particles from entering the fuel line and tends to separate water from the fuel. Vapor lock problems are reduced when using an electric pump because the fuel is pushed from the tank under pressure rather than being pulled under vacuum, a condition that produces vapor. When the key is furst turned "ON" without the engine running, the ECM turns a fuel pump relay "ON" for two seconds . This builds up the fuel pressure quickly . If the engine is not started within two seconds, the ECM shuts the fuel pump "OFF" and waits until the engine starts . As soon as the engine is cranked, the ECM turns the relay "ON" and runs the fuel pump . On the 5.7L engine in the G van and all other 5.7L or 7.4L engines in vehicles over 8500 GVW, a fuel module will override the ECM and the fuel pump will run for approximately twenty seconds . The fuel module corrects a hot restart (vapor lock) during a high ambient condition . 25055129(48508) 3975550 (4852() 15530354(48520) Figure 7-33 CAUTION : To reduce the risk of fire and personal injury, it is necessary to allow fuel pressure to bleed off before servicing fuel system components. (See "Fuel System Pressure Relief Procedure.") The in-line filter is located in the fuel feed line. It prevents dirt from entering the TBI unit. In-Tank Filter A woven plastic filter is located on the lower end of the fuel pickup tube in the fuel tank . The filter prevents dirt from entering the fuel line and, also, stops water, unless the filter becomes completely submerged in water. This filter is self-cleaning and normally requires no maintenance . Fuel stoppage, at this point, indicates that the fuel tank contains an abnormal amount of sediment or water; the tank should, therefore, be thoroughly cleaned. FUEL AND VAPOR PIPES The fuel feed and return pipes and hoses extended 7-35 SECTION 7D - ENGINE FUEL SYSTEMS from the fuel pump and sender to the TBI unit. They are secured with clamps and are routed along the frame side member . to a vapor canister and then vapors are purged into the intake manifold air flow and consumed in combustion . The vapor pipe and hoses extend from fuel pump and sender unit to the evaporative emission control vapor canister. DIESEL ENGINE SYSTEM DESCRIPTION FUEL TANK " " " " " The fuel tank, at the rear of the underbody, is held in place by two metal straps . Anti-squeak pieces are used on top of the tank to reduce rattles. Filler Neck To help prevent refueling with leaded gasoline, the fuel filler neck on a gasoline engine vehicle has a built-in restrictor and deflector . The opening in the restrictor will only admit the smaller unleaded gas nozzle spout, which must be fully inserted to bypass the deflector. Attempted refueling with a leaded gas nozzle, or failure to fully insert the unleaded gas nozzle, will result in gasoline splashing back out of the filler neck. Fuel Filler Cap The fuel tank filler neck is equipped with a screw-type cap . The threaded part of the cap requires several turns counterclockwise to remove . The long threaded area was designed to allow any remaining fuel tank pressure to escape, while the cap was being removed . A built-in torque-limiting device prevents overtightening . To install, turn the cap clockwise until a clicking noise is heard. This signals that the correct torque has been reached and the cap is fully seated . EVAPORATIVE EMISSION CONTROL The system transfers fuel vapors from the fuel tank inINJECTOR PUMP The 6.2-liter diesel engine fuel system is composed of: Fuel tank with water sensor and screen filter Primary fuel filter Mechanical fuel pump Secondary fuel filter Fuel line heater Injection distributor pump " High pressure lines " Fuel injection nozzles . Fuel is pulled from the fuel tank by the mechanical pump which is located on the right side of the engine . It is driven by an eccentric lobe on the camshaft through a pushrod. Fuel is pulled through the primary filter, by the mechanical pump. Fuel is then pumped through the fuel line heater and through the secondary filter mounted on the inlet manifold . Both filters remove foreign material which could damage the injection pump or clog the injector nozzle . From the filter, the fuel is pumped to the injection pump. (See Figure 7-25.) The 6.2-liter injection pump is mounted on top of the engine under the intake manifold . It is gear driven by two gears - one attached to the front end of the camshaft which drives the second gear that is attached to the end of the injection pump shaft . These two gears are the same size and have the same number of teeth ; thus, the injection pump shaft turns at the same rate as the camshaft and one-half the speed of the crankshaft. The pump will turn in the opposite direction to that of the camshaft and crankshaft. SECONDARY FILTER - VARIES BY MODEL & YEAR (AC PART NO. TP943 - SPIN-ON TYPE) (AC PART NO. T936 - SQUARE-SHAPED TYPE) PRIMARY FUEL FILTER (AC PART NO. T944) INJECTOR NOZZLES (8) Figure 7-34 - Diesel Engine Fuel System 7-36 WATER DRAIN SIPHON VALVE SECTION 7D ENGINE FUEL SYSTEMS The injbction pump is a high-pressure rotary-type pump that directs a metered, pressurized fuel through the high pressure tubes to the eight injector nozzles . The eight high pressure lines are all the same length although their shapes may be different. This prevents any difference in timing, cylinder to cylinder. PRIMARY FUEL FILTER (MOUNTED ON FRAME RAIL P-SERIES) The fuel line heater operates when the ambient temperature is low enough to require heating of the fuel. MAINTENANCE AND INSPECTION WATER IN FUEL The diesel engine has a "water-in-fuel" warning system allowing the user to guard against water in fuel, which is very critical in diesel engines . The fuel tank is equipped with a filter which screens out the water and lets it lay in the bottom of the tank below the fuel pickup . When the water level reaches a point where it could be drawn into the system, a warning light flashes in the cab . A siphoning system starting at the tank and going to the rear spring hanger on some models and at the midway point of the right frame rail on other models permits the user to attach a hose at the shut-off and siphon out the water. Figure 7.35 - Primary Fuel Filter (AC Type T944) A primary filter (Figure 7-26) is located on the front of the dash and it also has water-draining provisions. 30 FT. LBS. A secondary in-line fuel filter (Figure 7-27) is the final filter before fuel enters the injection-pump . See Appendix 7-8 - Secondary Fuel Filters at the back of this section of the manual for additional equipment operation information . When changing the fuel filter or when the vehicle has run out of fuel, disconnect the connector .from the temperature switch and jumper connector terminals . This will aid in purging air from the pump. (This procedure is necessary only on a hot engine, as the circuit will always be closed when the engine is cold.) PRIMARY FUEL FILTER WATER DRAIN If it should become necessary to drain water from the fuel tank, check the primary fuel filter (Figure 7-26) for water. This can be done as follows : 1 . Open the petcock on the top of the primary filter housing . 2. Place a drain pan below the filter and open the petcock on the bottom of the drain assembly . (A length of hose is attached to the petcock to direct drained fluid below the frame.) 3. When all water is drained from the filter, close the petcock firmly. Figure 7-36 - Secondary Fuel Filter (AC Type TP943) NOTE: If the filter is completely drained, remove the filter and refill it with clean diesel fuel to prevent engine stalling . 4. Close the upper petcock tightly . 5. Start the engine and let it run briefly . The engine may run roughly for a short time until the air is purged from the system . 6. If the engine continues to run roughly, check that both petcocks at the primary filter are closed tightly . 7-37 SECTION 7D ENGINE FUEL SYSTEMS SECONDARY FUEL FILTER (See Figure 7-27) Tighten Removal 1 . Bleed air from the fuel manager/filter as follows : a. Open the air bleed valve on top of the fuel manager/ filter assembly. b. Connect a hoseto the air bleed valve located on top of the element assembly and place the other end of the hose into a suitable container . 1 . Remove the fuel filter lines from the adapter. 2. Remove the fuel filter adapter from the intake manifold . 3. Remove the filter. Installation Anytime either of the fuel filters is removed or replaced, refill it with clean diesel fuel to prevent engine stalling after start-up, and to avoid very long engine cranking time. 1 . Install the filter to the adapter. 2. Install the adapter to the intake manifold . 3, Install the fuel filter lines. 9 Tighten the element nut (7) securely by hand. CAUTION : THE WATER/DIESEL FUEL MIXTURE IS FLAMMABLE, AND COULD BE HOT. TO HELP AVOID PERSONAL INJURY AND/OR PROPERTY DAMAGE, DO NOTTOUCH THE FUEL COMING FROM THE DRAIN HOSE, AND DO NOT EXPOSE THE FUEL TO OPEN FLAMES OR SPARKS. BE SURE YOU DO NOT OVERFILL THE CONTAINER . HEAT (SUCH AS FROM THE ENGINE) CAN CAUSE THE FUEL TO EXPAND. IF THE CONTAINER IS TOO FULL, FUEL COULD BE FORCED OUT OF THE CONTAINER . THIS COULD LEAD TO A FIRE AND THE RISK OF PERSONAL INJURY AND/OR VEHICLE DAMAGE . DIESEL FUEL MANAGER/FILTER ELEMENT REPACEMENT 6.5L MODEL FM 100 (See Figure 7-28) Removal 1 . Remove the fuel filler cap to release any pressure or vacuum in the fuel tank. 7. 8. 9. 10 . 11 . 12 . 14 . 15 . 16. 18. 2. Remove the element nut (7) turning it by hand in a counter-clockwise direction . If unable to turn by hand, a strap wrench (oil filter type) may be used to "break loose" the element nut . 3. Remove the element (8) by lifting it straight up and out of the heade assembly (9) . It is not unnecessary to drain fuel from the header assembly (9) to change the filter element (8) since the fuel will remain in the header assembly's cavity. NUT, ELEMENT ASSEMBLY, ELEMENT ASSEMBLY, HEADER SEAL, WATER SENSOR ASSEMBLY, WATER SENSOR SCREW, SENSOR MOUNTING SEAL, CAP ASSEMBLY, HEATER NUT, CAP CAP, AIR BLEED Important Make sure the mating surface between the element assembly and the header assembly is clean before installation . Installation 1 . Install the new element assembly by aligning the widest key slot located under the element assembly cap with the widest key in the header assembly. Push the element in a downwards direction until the mating surfaces make contact . V2639 2. Install the element nut (7) . Figure 7-28 - Diesel Fuel Manager/Filter (6.5L) 7-38 SECTION 7D ENGINE FUEL SYSTEMS c. Disconnect the fuel injection pump shut-down solenoid wire . d. Crank the engine in 10 to 15 second intervals until clear fuel is observed at the air bleed hose (wait for one minute between cranking intervals) . e. Close the air bleed valve. f. Connect the shut-down solenoid wire and reinstall fuel filler cap. 9. Start the engine and allow to run for five minutes at idle. h. Check the fuel manager/filter for leaks. FUEL PUMP REPLACEMENT (See Figure 7-29) Removal 1 . Remove the negative (-) battery cable(s) . 2. Remove the electrical wiring from the pump. 3. Remove the harness from the pump support bracket . 4. Remove fuel lines from the pump. 0 Use two wrenches to remove the lines . 5. Remove the pump support bracket screws. 6 . Remove the support bracket from the brake lines. 7. Remove the pump and bracket from the frame rail. Installation 1 . Install the pump and bracket to the frame rail. Figure 7-29 - Pump # 6442656 - Fuel Pump Location Make certain that there is sufficient fuel in the tank. " Check for leaks at all fuel connections from the fuel tank to the injection pump. Tighten any loose connections . With the engine running, check all hoses and lines for flattening or kinks that would restrict the flow of fuel . " Air leaks or restrictions on the suction side of the fuel pump will seriously affect pump output . FUEL PUMP FLOW TEST 2. Install the support bracket to the brake lines. 1 . Remove the fuel line at the fuel filter inlet . 3. Install the pump support bracket screws. 2. Disconnect the fuel injection pump electric shut-off solenoid wire (pink wire) . 4. Install the fuel lines to the pump. Use two wrenches to install the lines. 3. Place a suitable container at the end of the fuel filter inlet line. 5 . Install the wiring harness to the support bracket . 4. Crank'the engine . for 15 seconds . 6. Install the electrical wiring to the pump. 5. The fuel pump should supply 237 ml (1/2 pint) or more in 15 seconds . 7. Install the negative (-) battery cable(s) . Inspect Inspect the fuel lines between fuel filter and tank for restrictions . Inspect the fuel tank sending unit for restrictions . If "OK" replace the fuel pump. 6. Install the fuel injection pump electric shut-off solenoid wire (pink wire). 7. Install the fuel line at the fuel filter inlet . 0 If the system fails to pass the above test: Inspect FUEL PUMP TESTS If the fuel system is suspected of not delivering enough fuel, it should be inspected as follows and both the "Fuel Pump Flow Test" and the "Fuel Pump Pressure Test" should be performed . 7-38A Inspect the fuel lines between fuel filter and tank for restrictions. Inspect the fuel tank sending unit for restrictions . If "OK" replace the fuel pump. SECTION 7D - ENGINE FUEL SYSTEMS FUEL PUMP PRESSURE TEST 1 . Remove the fuel line at the fuel filter inlet . 2 . Disconnect the fuel injection pump electric shut-off solenoid wire (pink wire) . 3. Install a low pressure gage to the line. 4. Crank or run the engine for 10 to 15 seconds . 5. Fuel pressure should be 40 to 60 kPa (5 .8 to 8.7 psi). 6. Connect the fuel injection pump electric shut-off solenoid wire (pink wire) . 7. Install the fuel line at the fuel filter inlet. If the system fails to pass the above test: APPENDIX 7-6 PLUGGED FUEL RETURN LINE AND ENGINE PERFORMANCE The following information has been extracted from a Chevrolet Dealer Service Technical Bulletin and concerns poor engine performance due to a plugged fuel return line on the G-30 Cutaway and P-Series Class A 'Rail. Reference : Chevrolet Dealer Service Technical Bulletin No. 78-I-53 (September, 1978) Effective with 1980 model production, an improved flexible hose was also introduced into production for the Class A Motor Home chassis . The new hose resists "sucking shut" in high heat and high fuel demand situations ; however, it still will draw closed if tank or line filters become plugged . (GM Part No. 14026551 for 454 engines and GM Part No. 14026550 for 350 engines .) Prior to Cutaway and Class A Rail body completion, a temporary fuel tank was utilized and required that the fuel return line remain disconnected and plugged. The line was to be unplugged and connected by the body builder prior to final delivery of the completed vehicle . Failure to reconnect the fuel return line can cause a vapor lock condition at high altitudes or high ambient temperatures . FUEL FEED FRONT PIPE FUEL PUMP 1 ASSEMBLY In the event of a lack of power or rough engine complaint on the subject vehicles, check for the proper connection of the fuel return line . (See Figure A7-6-1 .) NOTE: , Some 1978 and 1979 "G" Vans with V-8 engines, when operated in high ambient temperatures and under high engine fuel demands, have experi enced the deformation of the flexible hose which connects the fuel feed line to the fuel pump. (See Figure A7-6-1 .) This condition is difficult to diagnose due to the unusual conditions under which it takes place . To prevent this hose from deforming, a new molded hose (GM Part No. 14010036) has been released for 1980 production and can also be used for service replacement . FUEL RETURN FRONT PIPE FUEL RETURN HOSE (32) MODELS EXCEPT DIESEL ENGINE FigureA7-6-1-- Fuel Return Line Connections APPENDIX 7.7 VAPOR LOCK CAUSE AND CURE The following information has been compiled from extensive research and testing performed by Chevrolet Engineering and RV manufacturers concerning fuel handling problems of the Class A Motor Home (during 1982 and 1983) . Chevrolet and the RV manufacturers examined typical "problem units" furnished by various owners in order to better understand "real-world" vapor lock problems in the highly customized Class A Motor Home and develop corrective actions . This information is presented as an aid to the motor home owner in understanding the problems associated with vapor lock and their suggested solutions . Fuel System Plumbing As determined from initial studies, Chevrolet engineers and RV manufacturing representatives determined that part of the problem concerning vapor lock involved the RV manufacturers' approach to the fuel system plumbing . Examination of problem units identified considerable plumbing errors, such as : " Four feet of rubber hose added in the middle of the stretch chassis . " A length of hose positioned over the top of the tank to the pickup . " Total rubber plumbing which is tied to the rear hot water lines with zip straps so that there was a tendency for the fuel to boil and the lines to "suck shut" or kink at each zip strap. " Vehicles equipped with a defective switch valve so that the ports did not line up properly and some of the valves would only switch occasionally . (Ports that did not line up caused restriction as did units that had two additional fuel filters and a stretch chassis . All of these factors add to the load on the mechanical fuel pump.) to the cause of vapor lock by the addition of alcohol to the fuel without informing the public or advertising the fuel as gasohol . Also, it was determined that butane was added to "cover up" lower grade crudes and to increase octane ratings . The result of the fuel being adjusted and the octane modifiers was a general increase in the Reid vapor pressure (RVP) of the fuels (the higher the Reid vapor pressure the greater the possibility of vapor lock) . The average Reid vapor pressure of regular unleaded gasoline was 9.3 in 1980, 9.8 in 1981 and 10.3 in 1982 (with individual locations showing a reading of 12 and 13) . With fuel changes toward the higher Reid vapor pressure fuels, some motor home owners who have never experienced any problems could have vapor lock problems that did not exist a year or so ago . Also, it was determined that mountains, steep grades and overloaded vehicles tend to aggravate the vapor lock problem, as recorded in a park survey at Pikes Peak. Vapor lock at Pikes Peak is the single most recorded mechanical problem encountered. Results of Vapor Lock Investigation During the week of October 17, 1983, Chevrolet invited all Class A Motor Home manufacturers to the GM Proving Grounds in Phoenix, Arizona. The purpose of this meeting was to discuss the findings of the investigation into the cause . of vapor lock and to make specific corrective recommendations for current and future production vehicles (including changes in truck emissions) . The meeting was attended by 34 of 36 RV manufacturers . Chevrolet suggested that the RV manufacturers incorporate the following recommendations into current and future vehicle building, as well as develop some adaptation for problem units already existing in the field . The following recommendations were presented : " An electric fuel pump installed in the return line rather than the suction line . A one-half inch steel fuel line mounted on the outside of the frame rail, protected against rub and chafe (see Figure A7-7-2) . Incorrect tank cap venting . " Also recommended is a pump bypass line along with a check valve. The 12-801 is a positive displacement pump and will not allow fuel flow if it stops running . The bypass, which closes under fuel pressure, will allow the engine mounted mechanical pump to pull fuel from the tank in the event of an electric pump failure. (See figure A7-7-1) . And so on . Chevrolet and the RV manufacturers' representatives determined that 100 percent of the motor homes produced with . plumbing errors such as those above could have vapor locking problems . Investigation showed that a properly plumbed fuel system down the inside of the frame rail was also not a 100 percent cure for the problem. Fuel Properties " The fuel requirements for the 454 engine at wideopen throttle are 25 gallons per hour at 2 PSI minimum and 3 PSI maximum . If fuel line lengths or routings create a situation where this cannot be met, an electric pump should be added at the fuel tank to supply fuel to the mechanical pump on the engine . Pressure in the supply line will further reduce the chance of bubbles forming versus a negative pressure situation with a mechanical pump only. (See Pressurized Fuel System Diagnosis Chart in Figure A7-7-8.) As part of the investigation, Chevrolet Fuel and Lubrication Engineers conducted a nationwide survey examining the possibility that fuels could cause vapor lock. Results of the survey show that oil companies have contributed 7-40 APPENDIX 7-7 VAPOR LOCK CAUSE AND CURE (Cont'd) " A single in-line filter should be placed between the tank and the electric fuel pump. (One filter choice is AC Part No . GF62C.) " A 3/8-inch rubber fuel line connection should be made at the mechanical fuel pump and at the fuel pump sending unit. " Power for the electric fuel pump should be controlled through a relayorspecial oil pressure switch to assure shut-down in the event of vehicle upset (see Figure A7-7-3). Consideration could be given to a manual priming override in the event the system has totally run out of fuel. Normal starts would occur with the fuel remaining in the carburetor and upon starting as oil pressure came up the special switch or relay and would turn on the electric pump. (See installation instructions in Figure A7-7-4 .) Check Valve Installation To install a fuel line anti-siphon check valve into the system, a 3/8" bypass line must be installed around the electric fuel pump and regulator (See Figure A7-7-1.) The valve is manufactured by Aluminum Fabricated Products (AFP 200) and must be fitted with 3/8" hose connector, available from Parker-Hannifin Corporation (Part No. 126HBL-6-6.) These parts are usually available from marine hardware suppliers . Install as follows : Install one 3/8" T-fitting in the fuel line between the regulator and the mechanical fuel pump and one 3/8" T-fitting between the electric fuel pump and the fuel tank. " Connect a 3/8" hose to the T's . " AC electric fuel pump (AC Part No. EP89) can also be used and does not require a fuel pressure regulator . The wiring remains the same. Chevrolet invited all RV manufacturers to the Phoenix meeting to share the findings and test information, as it would be difficult for a singular RV manufacturer (or customer) to produce these tests on their own . Chevrolet informed the RV manufacturers that all necessary steps would be taken to correct any vapor lock problem on any chassis with a 137-, 158-, 178-inch wheelbase with a 100 percent factory system . As an additional commitment to the 1983 meeting, Chevrolet has informed all RV manufacturers that all necessary steps will be taken to correct any vapor lock problem for the 208-inch wheelbase Model CP32032 entering production for the 1988 model year with a 100 percent factory system . Additionally, Chevrolet requested that the RV manufacturers correct any field problems that are reported to them on any units that have been modified by the RV manufacturer - such as stretch chassis, dual tanks, dual fuel, oversize tanks, etc ., as the individual manufacturers are more knowledgeable of their own systems and are in a better position to make their own modifications for the various models, years and options . If the bypass fuel line is already in place, remove 1-1/2,inches of 3/8 fuel line and insert check valve. " Insert valve side in line toward mechanical fuel pump; insert fitting side into line from fuel tank. NOTE: Chevrolet has completed testing of a new 60gallon tank. With the start of 1985 production, new fuel lines were installed on the outside of the frame rail. In the spring of 1985, a complete system was in production with in-tank electric pusher pump and external regulator adjustable by the RV manufacturer for an oversize wheelbase . (See Figure A7-7-5.) " Secure bypass line and valve with 3/8" hose clamps . 7-41 ELECTRIC FUEL PUMP REGULATOR FROM FUEL TANK To MECHANICAL FUEL PUMP 11/2 " 3/8" TEE CHECK VALVE AFP200 3/8' HOSE FEMALE FITTING PARKER N126HBL-66 0 0 oi ° 0 Figure A7-7-1 APPENDIX 7-7 VAPOR LOCK CAUSE AND CURE (Cont'd) 3/8" RUBBER LINE 1/2" STEEL LINE 3/8" RUBBER LINE ELECTRIC FUEL PUMP & REGULATOR FUEL FILTER MECHANICAL FUEL PUMP Figure A7-7-2 - 1984 Recommended Field Fix IGNITION + 12V OIL PRESSURE SWITCH GM PART NO. 3986857 ELECTRIC FUEL PUMP RELAY SWITCH GM PART NO. 356284 CONNECTOR 12101921 WITH LOCK 12010259 CAN BE USED AS THE ELECTRICAL CONNECTION FOR EACH OF THESE SWITCHES . NOTE: THE FOLLOWING OIL PRESSURE SWITCHES CAN BE USED WITH OR WITHOUT A RELAY SWITCH AND ARE CAPABLE OF HANDLING CURRENT DRAW REQUIREMENTS OF THE HOLLEY GPH 110 (PART NO. 12-801) MAX-PRESSURE PUMP. GM PART NO. 25036851 457874 14034354 HOLLEY ALSO PRODUCES A SWITCH (PART NO. 12-810) THAT DOES NOT REQUIRE A RELAY . CONNECTION 1/8 - 27 DRYSEAL (NPTF) 1/8 - 27 DRYSEAL (NPTF) 1/4 - 18 DRYSEAL (NPTF) Figure A7-7-3 - Electric Fuel PumpfOil Pressure Switch Relay 7-42 APPENDIX 7-7 VAPOR LOCK CAUSE AND CURE (Cont'd) TO ACCESSORIES GROUND ELECTRIC PUMP OIL PRESSURE SWITCH COIL Figure A7-7-4 - Oil Pressure Switch - Typical Wiring Diagram INSTALLATION INSTRUCTIONS NOTE : The pump oil pressure switch will normally have three terminals marked : C (common), NC (normally closed), and NO (normally open) . 1 . Disconnect cable from battery. 6 . Connect the fuel pump (black lead) to the terminal marked "C ." In this line, add an in-line fuse holder and a 7.5-amp fuse . NOTE : Please read instructions completely before making installation . 2. Remove original equipment oil pressure switch and retain . 3. Screw a 1/8-inch pipe nipple into the hole from which the pressure switch was removed . Use any suitable thread sealant on all fittings, taking care to avoid an excess which might contaminate the engine . 4. Screw a 1/8-inch pipe tee onto the nipple and position it in a manner to facilitate the installation of the original oil pressure switch and the new fuel pump pressure switch in the remaining two holes. 5. Screw in the two switches and reconnect the lead to the original equipment oil pressure switch . 7. Connect the terminal marked "NO" to the ON terminal of the ignition switch . 8. Connect the terminal marked "NC" to the starter motor circuit. 9. To complete the installation, connect the ground cable to the battery. BE SURE TO CRIMP SECURELY ALL ELECTRICAL CONNECTORS AND CLEAN ANY AREA WHERE GROUND LEADS WILL BE FASTENED. 7-43 APPENDIX 7-7 VAPOR LOCK CAUSE AND CURE (Cont'd) 1985 112 THRU 1989 PRODUCTION SYSTEM 1/2-INCH RUBBER LINE GM PART NO. 15530403 FUEL FILTER GM PART NO. 25055347 AC TYPE GF-509 1/2 INCH STEEL LINE MECHANICAL FUEL PUMP ENGINE ELECTRICAL RELAY GM PART NO. 15528707 OIL PRESSURE SWITCH SEE 1 .800 GROUP FORWARD LINE NS REAR LINE NS REGULATOR GM PART NO. 15598336 . HI PRESSURE HOSE GM PART NO.: 15530451-40 GAL . 15530401-60 GAL. 40 GAL . TANK GM PART NO. 14042352 60 GAL. TANK GM PART NO. 14042378 40 GAL. IN TANK PUMP GM PART NO. 6472311 60 GAL. IN TANK PUMP GM PART NO. 6472526 40 GAL. TANK STRAPS GM PART NO. 472286 60 GAL . TANK STRAPS GM PART NO. 15597850 Figure A7-7-5 - 1985 112 to 1989 Pressurized Fuel System Components NOTE : In July, 1985, GM began production of a new pressurized fuel system . From production, the RV manufacturer may choose a 40-gallon standard system, an optional 60-gallon system (Option No. NN4) or specify Option No. 9H2. Option No. 9H2 deletes Chevrolet's system and requires the manufacturer to install its own system . Check the Service Parts Identification Label for appropriate option number . See page 1-3 . NOTE : The factory electric in-tank fuel pump has an activating relay that is shipped loose in the parts box to the RV manufacturer. The wire harness is located at the left front corner of the engine compartment. There are two studs on the engine side of the tow pan for mounting the relay. See Figure A7-17-2 for mounting location. APPENDIX 7-7 VAPOR LOCK CAUSE AND CURE (Cont'd) 1990-1993 PRODUCTION SYSTEM FUEL INJECTION FUEL FILTER GM PART NO. 25055052 AC TYPE GF481 FUEL LINES RUN INSIDE OF FRAME 11:411M'101i ENGINE ELECTRICAL RELAY GM PART #10052954 OIL PRESSURE SWITCH SEE 1 .800 GROUP FUEL LINES NS FUEL TANK OPTIONS STD . 40 GALLON NN4 60 GALLON NJ9 80 GALLON RH OR LH FILL 40 GAL . FUEL SENDER GM PART NO. 25094633 PEW 60 GAL . FUEL SENDER GM PART NO. 25094631 PEX 80 GAL . FUEL SENDER GM PART NO. 25094783 PEY FUEL SENDER TO TANK SEAL GM PART NO. 3893116 FUEL PUMP FITS ALL 3 GM PART NO. 6472763 FUEL IN TANK FILTER GM PART NO. 25055455 Figure A7-7-6 NOTE: Viton hose and clamp Kit #25028041 for short hose between electric fuel pump and fuel meter in tank. Fuel Hoses 1990-92 Pressure line tank to rail line 15666408 Pressure line, rail to injector 15613689 Return line, injector to rail line 15613690 Return line, rail line to tank 15666409 Temporary fuel line usage was eliminated SOP 5-31-91 . 1994 40 GAL. WITH PUMP GM PART NO . 25028266 60 GAL. WITH PUMP GM PART NO . 25028269 80 GAL. WITH PUMP GM PART NO . 25028272 PUMP ONLY GAS GM PART NO . 6443146 DIESEL METEOR ONLY 40 GAL. GM PART NO . 25027045 60 GAL. GM PART NO . 25004132 80 GAL. GM PART NO . 25029695 LIFT PUMP 1994 7.4 GAS 40 GAL. FUEL SENDER GM PART NO. 25028266 60 GAL. FUEL SENDER GM PART NO. 25028269 80 GAL. FUEL SENDER GM PART NO. 25028272 FUEL PUMP GM PART NO. 6443146 1994 6.2 DIESEL 40 GAL. FUEL SENDER GM PART NO. 25027045 60 GAL. FUEL SENDER GM PART NO. 25004132 80 GAL. FUEL SENDER GM PART NO. 25029695 LIFT PUMP GM PART NO . 6442656 APPENDIX 7-7 VAPOR LOCK CAUSE . AND CURE (Cont'd) m Figure A7-7-7 - Engine Electrical Fuel Pump Relay - Typical Wiring Diagram NOTE: Without activation of the electric in-tank fuel pump, the chances for a vapor lock in the system increases because of the increased workload on the mechanical pump through the electric pump. To check the system, perform the following operational test. Turn the ignition key to the RUN position. Have an assistant check (listen/feel) the tank end for pump operation as a capacitor charges in the relay. The pump will run for approximately five seconds after the key has been turned . (Twelve volts is also supplied to the pump in the crank position and as the engine starts and oil pressure builds, 12 volts is supplied to the electric fuel pump whenever the engine is running .) APPENDIX 7.7 VAPOR LOCK CAUSE AND CURE (Cont'd) 1985 112 Through 1989 Model Year Verify that the coach was built with a Chevrolet fuel tank or that it contains an electric intank fuel pump. This can be done by checking the invoices or Service Parts I.D. Label . A 40-gallon tank is standard. Option NN4 indicates a 60-gallon tank was installed . Option 9H2 indicates that the fuel system was installed by the coach builder and may not be of Chevrolet design. Once the system has been identified, determine that the electric fuel pump is operating, as follows . " With transmission in PARK position and emergency brake ON, turn ignition ON . DO NOT START ENGINE . " Have someone hold their hand against the bottom of the fuel tank . " A vibration should be felt on the hand for approximately 5 seconds after the ignition is turned on. If the pump does not operate, and a vibration is not felt, check the fuel pump relay system wiring (see page 7-43 and 7-96 for location) . Check electrical continuity from electric fuel pump relay (Fig. A7-7-3) to oil pressure switch and from oil pressure switch to electric fuel pump. It is the responsibility of the coach manufacturer to in- sure that the electric fuel pump operates properly at time of coach assembly . If the coach does not have an electric fuel pump, or was built before 1985 1/2, use the diagnostic chart on page 7-48. Gas Fumes in Engine Compartment or Fuel in Charcoal Canister 1 . Remove line from charcoal canister that runs to the fuel tank. 2. Remove gas cap from filler spout. 3. Blow air into disconnected canister line (Tank must be at least 1/4 full.) 4. Listen at spout for bubbles in the fuel tank. 5. If air bubbles in gasoline, the lines are crossed . This condition usually occurs when the coach manufacturer has stretched the frame and the fuel lines have been extended. Look for a crossed line where the fuel lines have been spliced . If blowing air into the disconnected line does not cause bubbles, check for damage to fuel lines, to the canister, and the valve on top of canister. (Fig. 7-96) APPENDIX 7-7 VAPOR LOCK CAUSE AND CURE . (Cont'd) INSTALL PRESSURE GAGE AT CARE. RUN ENGINE AT IDLE. PRESSURE AT CARIB . INLET ABOVE 5 PSI PRESSURE 11/2 to 5 PSI SYSTEM O.K. AT IDLE PRESSURE ROAD TEST AND OBSERVE GAGE AT PROBLEM ROAD SPEED PRESSURE 11/2 to 5 PSI SYSTEM O.K . PROBLEM ELSEWHERE PRESSURE 0 to 1 1/2 PSI ADD ELECTRIC PUMP . SUGGEST HOLLEY 12-801 PUMP WITH HOLLEY 12-810 PRESSURE SHUT-OFF SWITCH. INSTALL AC-GF62C FILTER PRIOR TO PUMP AND REGULATOR . INSTALL AS CLOSE TO TANK AS POSSIBLE . REMOVE ANY OTHER LINE FILTERS BETWEEN TANK AND CARB . ADJUST REGULATOR TO OBTAIN 4-5 PSI MECHANICAL PUMP INLET WITH ENGINE RUNNING AT IDLE AND WITH RETURN LINE HOOKED UP AND FUNCTIONAL : 454 ENGINE REQUIRES HIGH-VOLUME PUMP AS ENGINE CAN USE 25 GALLONS OF FUEL PER HOUR AT WOT. FUEL SUPPLY LINE SHOULD BE ROUTED OUTSIDE THE FRAME RAIL FOR HEAT . SHIELD . 1/2 INCH PREFERRED WITH 3/8 INCH REDUCING ENDS . RUN FULL LENGHT AS SMOOTH AND UNBROKEN AS POSSIBLE SECURED FOR NO CHAFE OR RUB . USE STEEL LINES WITH RUBBER CONNECTIONS AT ENDS. PRESSURE ABOVE 5 PSI, EQUIPPED WITH ELECTRIC PUMP AND RETURN LINE HOOKED UP EQUIPPED WITH ONLY MECHANICAL PUMP ADJUST OR INSTALL A PRESSURE REGULATOR SET TO 45 PSI AT ENGINE IDLE DISCONNECT RETURN LINE AT MECHANICAL PUMP AND WITH A TEMPORARY TEST HOSE RETURN FUEL TO A GALLON JUG UNDER VEHICLE PRESSURE 11/2to5PSI PRESSURE ABOVE 5 PSI SYSTEM NORMAL REGU LATOR DEFECTIVE ABOVE 5 PSI PRESSURE 11/2 to 5 PSI RESTRICTEDPINCHED RETURN LINE BACK TO TANK DISCONNECT ELECTRIC TO PUMP AND BYPASS PLUMBINGTANK TO LINES TO MECHANICAL PUMP REPAIR-AIR PRESSURE SHOULD EASILY BLOW INTO TANK FOLLOW RETURN LINE DIAGNOSIS FOR NONELECTRIC PUMP RETEST WITH RETURN LINE RECONNECTED PRESSURE 11/2 to 5 PSI SYSTEM O.K . Figure A7-7-8 - Pressurized Fuel System Diagnosis Chart For Pre 1985 112 and Units NOTE : Cool fresh air should be introduced through the fresh air induction via hose from the front of the radiator to the carburetor air cleaner snout. This has proven effective in reducing fuel percolation in the carburetor fuel bowl . PRESSURE ABOVE 5 PSI REPLACE MECHANICAL PUMP, (RESTRICTED ORIFICE RETURN INSIDE PUMP) PRESSURE 11h to 5 PSI SYSTEM O.K . PRESSURE ABOVE 5 PSI LINE TOO SMALL OR STILL HAS A RESTRICTION APPENDIX 7-7 VAPOR LOCK CAUSE AND CURE (Cont'd) INSTALL REMOTE PRESSURE GAUGE AT MECHANICAL FUEL PUMP INLET LINE. RUN ENGINE AT IDLE . PRESSURE 0 PSI PRESSURE 4-5 PSI SYSTEM OK AT IDLE s SEE NOTE PAGE 7-46 FUEL PUMP DIAGNOSIS . CHECK FOR INOPERATIVE FUEL PUMP . CHECK & ADJUST PRESSURE REGULATOR TO 4 1/2 TO 5 PSI . ROAD TEST AND OBSERVE GAUGE AT PROBLEM ROAD SPEED PRESSURE 2-4 PSI PUMP INOPERATIVE-PERFORM FUEL PUMP RELAY SYSTEM DIAGNOSIS . A-KEY ON-5 SECONDS SHOULD HAVE CURRENT BOTH TERMINALS - IF ONLY ONE TERMINAL HAS 12 VOLTS - REPLACE RELAY #15528707 - LOCATION SEE PAGE 7-102 . RECHECK, FUEL PUMP FOR PRESSURE 4 1/2 TO 5 PSI AT IDLE UNIT REPAIRED . PRESSURE ABOVE 4-5 PSI SYSTEM OK PROBLEM ELSEWHERE 12 VOLTS AT BOTH TERMINALS PRESSURE 0-2 PSI CHECK ADJUSTMENT ON FUEL REGULATOR AND/OR CHECK FOR PLUGGED INLINE FUEL FILTER ON FRAME #GF 509 J REPLACE FILTER AND TEST AGAIN AT ROAD SPEED 2-4 PSI ADEQUATE. CHECK WIRING CIRCUIT FROM RELAY TO ALL PRESSURE SWITCH CHECK WIRING FROM RELAY TO ELECTRICAL SENDER AT TANK. DRAIN TANK AND REMOVE FUEL GAUGE AND PUMP - CHECK AND OR REPLACE FUEL PUMP . CAUTION: DO NOT TEST OR RUN FUEL PUMP ON BENCH OR IN DRY FUEL TANK - PUMP DAMAGE MAY RESULT - MUST BE TESTED IN LIQUID . PUMP RUNS - SET FUEL REGULATOR TO 4 1/2 to 5 PSI AT IDLE - ROAD TEST. CAUTION : Electric fuel pumps must never be tested dry. Can cause premature pump failure if not tested in liquid . Figure A7-7-9 - Pressurized Fuel System Diagnostic Chart 1985 112 thru 1989 UNABLE TO ADJUST REPLACE DEFECTIVE REGULATOR AND SET AT 4 1/2 TO 5 PSI . APPENDIX 7-8 TROUBLESHOOTING AFTERMARKET FUEL SYSTEMS The following information is presented as an aid to the motor home owner and RV manufacturers in understanding some of the problems and the suggested solutions for after-market fuel systems . This information has been extracted from a GM field representative research and testing report concerning problems with after-market fuel systems. Chevrolet and RV manufacturers examined typical "problem units" furnished by various owners to better understand aftermarket fuel system problems that are unknowingly built into a fuel system . GM has taken the position that any repairs to after-market fuel systems will be the responsibility of the RV manufacturer and/or the motor home owner. Problems associated with the vehicle fuel system will not be corrected under the GM warranty unless the system is a 100 percent GM fuel tank and system . (For additional information, see Appendix 7-7 - Vapor Lock Cause and Cure referring to the Chevrolet/RV Manufacturers meeting held in Phoenix, Arizona, October, 1983.) RESEARCH FINDINGS - Many RV manufacturer's customer service representatives have experienced customer complaints in several areas concerning aftermarket fuel systems . The three overall complaints are : 1 . Raw fuel is spilled out the vent to the ground or fills the charcoal canister . 2. The fuel tank fills slowly. 3. Raw fuel "shoots" from the tank when the fuel cap is removed . COMPLAINT No. 1 - The situation of raw fuel spilling out the vent to the ground can only occur when the fuel tank reaches a 100 percent "brim-full" condition . As there is no air pocket in the top of the tank, the fuel expands as it is heated and creates one of two possible situations. Either the fuel tank itself will bulge due to the expansion of the fuel, or the fuel escapes through the vent to the ground or the charcoal canister at a rate that is controlled by pressure and the size of the vent. COMPLAINT No. 2 - The "slow fill" complaint occurs on after-market fuel systems as the fuel entry point is positioned midway on the side of tank. This is a design "tradeoff" versus a top-fill or corner-fill fuel entry location. When the level of the fuel covers the fill opening in the side of the tank, the fill rate slows because the incoming fuel must move or "displace" the existing fuel out of the way. Also, the size of the vent and the spit-back tube have a bearing on the rate of fuel fill . Even if the top of the fuel tank was completely removed (similar in appearance to a pail), the fill rate would still be very slow as the incoming fuel must still move and displace the existing fuel . EXAMPLE : Filling a fuel tank would be much easier by pouring the fuel into the top to "splash" to the bottom versus filling the tank by forcing the fuel at the bottom of the pail which requires gravity to work against fluid weight and displacement . COMPLAINT No. 3 - Fuel "shooting" from the fuel tank when the cap is removed is caused by the vent being too small, and/or an incorrect position of the main side-fill fuel entry tube and spit-back tube. CASE STUDY EXAMPLE : An after-market fuel system was fitted with a spit-back tube extending approximately 1-3/8 inches into the fuel tank based on a planning design of 90 percent fill capacity of a tank 14 inches deep. (This is not enough of a margin of air space for all applications.) In this situation, when the fuel was above the half-way point of the tank, fuel was in the tank filler neck at the same level of the fuel in the tank. As the pressure increased in the tank from heat expansion and slightly restricted venting, the pressure was actually over the entire surface of the fuel . The moment the filler cap was removed, fuel rushed backward up the filler neck as the spitback tube could not bleed off the pressure fast enough. (This situation is similar to shaking a carbonated soft drink to obtain maximum "fizz," then turning the bottle or can upside down and opening the container slowly.) With a top-fill or corner-fill tank, (even with a restricted vent) the chance of fuel "spitting out" is greatly reduced as fuel is not present in the fill neck. The worst problem associated with a top-fill or corner-fill tank is air relief as the cap is removed . The problem of fuel "spit back" can be corrected for a side fill tank IF the pressure is removed from the top of the tank. APPENDIX 7-8 TROUBLESHOOTING AFTERMARKET . FUEL SYSTEMS (Cont1d) TO HELP CORRECT THIS CASE STUDY COMPLAINT : A design change is necessary in the restriction size of the vent line . As the size of the orifice is currently about a .030-inch opening, the above case study system would benefit by opening the vent hole to between .055 inch and .060 inch. This would allow additional pressure to bleed out of the top of the tank and to reduce downward pressure on the surface of the fuel. A restricted vent is needed for two reasons : " The restricted vent is required to make the automatic fuel shut-off work with the spit-back tube. " The restricted vent also serves as an anti-siphon device when the fuel runs to one end of the tank. A restricted vent that is too large defeats the purpose of the automatic shut-off and anti-siphon system . However, a restricted vent that is too small invites excessive pressure build-up in the tank. Ideally, the spit-back tube should be positioned in the tank to allow approximately 20 percent free air level. 'A top-fill or corner-fill system should be considered with the fill pipe extending into the tank to the same depth as the spit-back tube and cut at an angle horizontal to the fluid level. This remedy should be used in conjunction with a .055-inch to .060-inch restricted vent and a GM-type fill cap . ADDITIONAL TIPS - Troubleshooting after-market fuel systems does not end with tank hardware . Generally, pressure is a side effect of heated fuel causing expansion and fume pressures . A service technician should also examine the source(s) of the heat. Possible causes are : " A hole in the exhaust blowing directly on the fuel tank. " Serious overload or pulling of a trailer which puts abnormal "fire" in the exhaust . " An engine that is running poorly having higher than normal unburned fuel in the exhaust system which is burned off with the A.I.R. pump increasing exhaust temperatures . " An altered or modified exhaust system (by owner or RV manufacturer) with an improper tank-to-pipe clearance . APPENDIX 7.9 SECONDARY FUEL FILTERS The following information has been extracted from the GM 6 .2-Liter Diesel Engine manual . The information covers general operation, application and replacement part numbers of both the Model 75 and Model 80 Secondary Fuel Filter. G-P SERIES - MODEL 75 SECONDARY FUEL FILTER The G-P Series uses a Stanadyne Model 75 secondary fuel filter in 1983. (See Figure A7-9-1 .) It is fastened using two ball clips. It is particularly important to place absorbent towels under the filter when changing it to improve cylinder and case valley drain and prevent fuel oil contamination of the clutch-driven disc. The Model 75 filter is a two-stage pleated paper type filter . The first stage consists of approximately 400 square inches of filtering area and will remove 94 percent of particles 10 microns or larger. The second stage is made of the same paper material and consists of approximately 200 square inches of filtering surface . The second stage is 98 percent effective in filtering the fuel already filtered by the first stage. Particles which are larger than 10 microns may damage the pump's internal components. Figure A7-9-2 compares various micron sizes and will, ultimately show the filter's effectiveness . G-P SERIES - MODEL 80 SECONDARY FUEL FILTER The Model 80 Stanadyne Fuel Filter provides the following features in one unit: " " " " " " Two-stage fuel filter Fuel/water separator Electronic "water-in-fuel" signal Electric fuel heater Integral hand primer "Filter change" signal - removed starting 1989. Fuel Heater The purpose of the heater (see Figure A7-9-3) is to heat fuel, so that the filter does not plug with paraffin wax crystals. This will allow use of fuels at temperatures substantially below the Cloud Point of the fuel. The heater is electrically powered from the ignition circuit 39 and is thermostatically controlled to work when waxing of the fuel is expected . Figure A7-9-1 - Model 75 Secondary Fuel Filter The device can be divided into two major functional components - the heater and the power control assemblies . .003 INCH RELATIVE SIZE OF MICRON PARTICLES MAGNIFICATION 1000 TIMES 1 MICRON = .000039 INCH LOWEST VISIBILITY RANGE = 44 MICRONS ( .0017 INCH) HUMAN HAIR = .003 INCH 44 MICRONS Figure A7-9-2- Relative Size of Micron Particles 7-52 APPENDIX 7-9 SECONDARY FUEL FILTERS (Cont'd) The second stage is 98 percent effective in filtering the fuel already filtered by the first stage. Particles which are larger than 10 microns may damage the pump's internal components. Water Sensor The 6.21- uses a "water-in-fuel" warning system, which allows the user to guard against water in the fuel. The water is detected by a capacitive probe located in the filter base. Electronics within the probe will connect a ground (circuit 150) to the ground side of the "water-infuel" lamp (circuit 508) . This lamp is in the center of the instrument panel next to the glow plug lamp. In 1984 (4-wire water-sensor module) a bulb check was made anytime the ignition switch was in the start position . A "B+" signal on the purple wire at the "A" test switch (Figure A7-9-5) causes pin "D" to pull low, grounding the "water-in-fuel" bulb. In 1984-1/2 and 1985 (3-wire. watersensor module) when the ignition is turned on, the lamp will glow from 2 to 5 seconds, and fade away. This is done as a bulb check . FILTER CHANGE SIGNAL CONNECTOR OPTIONAL WATER DRAIN LOCATION WATER DRAIN "WATER IN FUEL" \ SIGNAL CONNECTOR OPTIONAL WATER DRAIN LOCATION Figure A7-9-3 - Model 80 Fuel Filter and Base Assembly BAT. NEG. (GROUND) Fuel Filter The engine fuel filter is a two-stage pleated paper type filter (see Figure A7-9-4) . The first stage consists of approximately 350 square inches of filtering area and will remove 96 percent of particles 5-6 microns or larger (see Figure A7-9-2) . The second stage is made of the same paper material with glass particles and consists of approximately 100 square inches of filtering surface . BAT. POS. (SWITCHED) SIGNAL LIGHT BAT. POS. (SWITCHED) TEST SWITCH BAT. NEG. BAT. POS . (SWITCHED) SIGNAL LIGHT (250 mA MAX.) '12VOLT D.C . SYSTEM Figure A7-9-5 - Filter Base Wiring Water Separator The bottom of the filter is a hollow water collector (Figure A7-9-6) . Because of the greater density of water, the water droplets will separate from the fuel oil . It will hold approximately 260 cubic centimeters of water (approximately 3-10 percent). Figure A7-9-4 - Model 80 Filter Cross Section A nylon/fiberglass coalescent is used to blend the small water droplets into larger ones. 7-53 APPENDIX 7-9 SECONDARY FUEL FILTERS (Cont'd) Fuel Flow See Figure A7-9-6 . Fuel enters at the top right inlet and flows into the heating chamber . The heater is activated at 8°C (46°F). and below. The heated fuel enters the element at the top and flows down through the two-stage WATER SENSOR Figure A7-9-6-Filter and Base Flow Schematic . fuel filter media pack . While passing through the third stage, water coalesces and drops to a sump holding area. Clean fuel returns to the base and exits.to the fuel injection pump. An electrical signal is obtained from the filterchange sensor located in the return path. SECTION 7E-ENGINE ELECTRICAL SYSTEM ENGINE EL ECTRICAL SYSTEM The engine electrical system is separate from the motor home "living" system . It consists of a chassis battery, starting (cranking) system, charging system, ignition system and instrument panel wiring and chassis information gages . 3. Reduced self-discharge compared to a conventional battery . This is important when a battery is left standing for long periods of time. BATTERY GENERAL DESCRIPTION 4. Comparable power available in a lighter and smaller case. RATINGS The battery is a device designed to store electrical power A battery has .two ratings : (1 .) a reserve capacity rating for later use. It performs this function through chemical _ at 80°F which is the time a fully charged battery will operate the vehicle with no generator operation, (2.) a cold action . crank rating at 0°F which indicates the cranking load caThe battery has three major functions in the electrical pacity . The Ampere/Hour rating formerly found on battersystem . First, it is a source of electrical energy for starting ies was based on the reserve capacity rating and is no the engine . Second, it acts as a voltage stabilizer for the longer used. electrical system . And third, it can, for a limited time, provide energy when the electrical load exceeds the output MAINTENANCE AND INSPECTION of the generator . A battery is not designed to last indefinitely ; however, with The sealed-top battery (Figure 7-28) is standard on all proper care, it will provide many years of service . If the battery tests as "good" but fails to perform satisfactorily vehicle lines. in service, the following are some of the more important factors that may point to the cause of the trouble . BUILT-IN 1 . Accessories left on overnight . HYDROMETER 2. Slow average driving speeds for short periods . 3. The vehicle's electrical load is more than the generator output particularly with the addition of aftermarket equipment such as radio equipment, air conditioning, window defoggers or light systems . 4. Defects in the charging system such as electrical shorts, slipping fan belt, faulty generator or voltage regulator . 5. Battery abuse, including failure to keep the battery cable terminals clean and tight or a loose battery (one that is not securely held in place). 6. Batteries in vehicles stored for long periods of time become discharged with sulfation occuring . Sulfation of the plates reduces the battery's capacity for accepting a charge. Also, under conditions of high ambient temperature, the temperature of the electrolyte may become excessive - causing boiling and loss of electrolyte . See Appendix B - Preparing The Motor Home For Storage for additional information concerning battery storage damage. Figure 7-28 - Sealed-Top Battery There are no vent plugs in the cover. The battery is completely sealed, except for two small vent holes in the side. These vent holes allow the small amount of gas produced in the battery to escape . The sealed-top battery has the following advantages over conventional batteries : 1 . No water addition for the life of the battery . This improvement makes the sealed-top battery possible. 2. Overcharge protection. If too high a voltage level is applied to the sealed-top battery, it will not accept as much current as a conventional battery ; the excess voltage will cause gassing, which leads to liquid loss. NOTE : The inspection and test procedures which follow apply for the Delco Sealed-Top Freedom Battery . If your vehicle is equipped with a conventional type and/or other brand battery, be sure to follow the test procedure and specifications recommended by the manufacturer. 7-55 SECTION 7E - ENGINE ELECTRICAL SYSTEM VISUAL INSPECTION The external condition of the battery should be checked periodically for damage such as cracked cover or case (Figure 7- 29) . Also check terminal area for loose or broken parts . HYDROMETER ,CRACKED OR BROKEN CONTAINER BUILT-IN HYDROMETER (DELCO SEALED-TOP BATTERY) The Delco sealed-top battery has a built-in temperaturecompensated hydrometer in the top of the battery. This hydrometer is to be used with the following diagnostic procedure. When observing the hydrometer, make sure that the battery has a clean top. A light may be required in some poorly lit areas to see the right indication . Under normal operation, two indications can be observed (Figure 7-30). BATTERY TOP CRACKED OR BROKEN COVER SIDE TERMINAL ADAPTER (AC-DELCO PART ST 1201) DARKENED INDICATOR (WITH GREEN DOT) DARKENED INDICATOR (NO GREEN DOT) LIGHT YELLOW OR BRIGHT INDICATOR MAY BE JUMP STARTED MAY BE JUMP STARTED DO NOT JUMP START Figure 7-30 - Built-In Hydrometer Figure 7-29 - Visual Battery Inspection CAUTION : BATTERIES PRODUCE EXPLOSIVE GASES, CONTAIN CORROSIVE ACID, AND SUPPLY LEVELS OF ELECTRICAL CURRENT HIGH ENOUGH TO CAUSE BURNS. TO LESSEN THE CHANCE OF PERSONAL INJURY, WHEN WORKING NEAR A BATTERY: " Always wear eye protection or shield your eyes . Do not lean over a battery. Remove all metal jewelry. " Never expose a battery to open flames or electric sparks . Also, do not smoke near a battery. " Do not allow battery acid to contact eyes or skin . Flush any contacted area with water immediately and thoroughly . Get medical help . " Do not allow metal tools to contact both the positive (red, "+") battery terminal (or any metal connected to this terminal) and any other metal on either vehicle at the same time . Make certain when attaching the jumper cable clamps to the positive terminals of the batteries that neither clamp contacts any other metal. " Batteries should always be kept out of the reach of children . GREEN DOT VISIBLE. Any green appearance is interpreted as a green dot and the battery is ready for testing. Do not charge the battery. 2. DARK - GREEN DOT NOT VISIBLE. If there is a problem with cranking, the battery should be tested following the Electrical Load Test in this section. But, before testing, the battery must be recharged until the green dot is visible . After charging, you may have to shake or tilt the battery slightly for the green dot to show . NOTE : A battery that has sat in a completely discharged condition or is extremely cold may not accept current for several hours after starting the charger. The charging and electrical systems should also be checked at this time . Occasionally, a third condition may appear : 3. CLEAR OR LIGHT YELLOW . This means the fluid level is below the bottom of the hydrometer . This may have been caused by excessive or prolonged charging, a broken case, excessive tipping or normal battery wearout. When finding a battery in this condition, it may indicate high charging voltage caused by a faulty charging system and therefore, the charging and electrical system may need to be checked. If a poor cranking condition exists and is caused by the battery, it should be replaced . 7-56 SECTION 7E ENGINE ELECTRICAL SYSTEM CAUTION : DO NOT CHARGE OR TEST THE BATTERY OR JUMP START THE VEHICLE WHEN THE HYDROMETER IS CLEAR OR LIGHT YELLOW AS THIS COULD RESULT IN PERSONAL INJURY (PARTICULARLY TO EYES) OR PROPERTY DAMAGE FROM BATTERY EXPLOSION OR BATTERY ACID. SEE CAUTION UNDER "VISUAL INSPECTION" IN THIS SECTION OF THE MANUAL . BATTERY TEST LOAD (AMPS .) 692, 83-50 150 693, 83-60 180 695, 87A-60 230 696, 89A-60 270 MINIMUM VOLTAGE TEMPERATURE (°F) Load Test Values ELECTRICAL LOAD TEST (DELCO SEALED-TOP BATTERY) Preliminary Steps 9.6 9.5 9.4 9.3 9.1 8.9 8.7 8.5 _ Minimum Voltage Dro If the battery has been on charge, remove the surface charge by connecting a 300-ampere load for 15 seconds . CAUTION : SEE CAUTION UNDER "VISUAL INSPECTION" IN THIS SECTION OF THE MANUAL. If the battery is in the vehicle, attach the voltmeter leads to the battery terminals . If the battery is out of the vehicle, attach the voltmeter leads to the side terminal adapters (AC-Delco Part ST-1201 or GM Part No. 1846855) on the battery . For Delco heavy-duty batteries with threaded stud terminals, attach the voltmeter leads to the snug-fitted terminal adapter ST-1201 ; or if not available, attach the leads between the lead pad and the bottom of the terminal hex nut . 70 60 50 40 30 20 10 0 Figure 7-31 - Battery Test Load Table and Voltage Drop Chart CAUTION : FAILURE TO OBSERVE THESE CONDITIONS OR PROCEDURES COULD RESULT IN SERIOUS PERSONAL INJURY (PARTICULARLY TO EYES) OR PROPERTY DAMAGE FROM SUCH CAUSES AS BATTERY ACID, A BATTERY EXPLOSION, ELECTRICAL BURNS AND/OR DAMAGE TO ELECTRONIC Test Procedure COMPONENTS OF EITHER VEHICLE INVOLVED. SEE 1 . Connect the voltmeter (preliminary steps) and apply CAUTION UNDER "VISUAL INSPECTION" IN THIS the test load to the value printed on the battery label . SECTION OF THE MANUAL. IN ADDITION : 2. Read the voltage after 15 seconds with the load connected . Be sure the jumper cables and clamps to be used for jump starting do not have loose or missing insulation. Do not proceed if suitable cables are not available . 3. Disconnect the load and compare the voltage reading with the chart in Figure 7-31 . If the voltage is less than the reading specified in the chart, replace the battery . If the reading is equal to or greater than that specified in the chart, the battery is good . If either battery has filler caps, check the fluid level. (Do not check using an open flame). If low, fill to the proper level with clear drinking water. Replace all caps before jump starting. Do not route the cable (or attach the clamp) on or near pulleys, fans, or 'other parts that will move when the engine is started . NOTE : Refer to battery top for additional load test amperes . JUMP STARTING - WITH AUXILIARY (BOOSTER) BATTERY NOTE: Do not push or tow the vehicle to start it. There are no provisions in the GM automatic transmission for engagement of the transmission to turn over the engine. Efforts to push or tow the vehicle to start it will have no effect . Both the booster and the discharged battery should be treated carefully when using jumper cables . Follow the conditions and procedure outlined below, being careful not to cause sparks . Follow the procedure listed below for jump starting the vehicle with an auxiliary booster battery . 1 . Set the parking brake firmly and place the automatic transmission in PARK (NEUTRAL for manual transmission). Turn off the ignition, turn off lights, and all other electrical loads. 2. Check the built-in hydrometer. If it is clear or light yellow, replace the battery, do not attempt to jump start . 3. Only 12-volt batteries can be used to start the engine . 7-57 SECTION 7E - ENGINE ELECTRICAL SYSTEM DO NOT ALLOW VEHICLES TO TOUCH! MON FIRST JUMPER CABLE DISCHARGED BATTERY SECOND JUMPER CABLE MAKE LAST CONNECTION ON ENGINE, AWAY FROM BATTERY BATTERY IN VEHICLE WITH CHARGED BATTERY Figure 7-32 - Jump Start Cable Connections NOTE: When jump starting a diesel engine vehicle with charging equipment, be sure equipment used is 12-volt and negative-ground. Do not use 24-volt charging equipment . Using such equipment can cause serious damage to the electrical system or electronic parts. 4. Attach the end of one jumper cable to the positive terminal of the booster battery and the other end of the same cable to the positive terminal of the discharged battery (Figure 7-32). Do not permit vehicles to touch each other as this could cause a ground connection and counteract the benefits of this procedure . 5. Attach one end of the remaining negative cable to the negative terminal of the booster battery, and the other end to a solid engine ground (such~as A/C compressor bracket or generator mounting bracket) at least 18 inches from the battery of the vehicle being started . DO NOT CONNECT DIRECTLY TO THE NEGATIVE TERMINAL OF THE DEAD BATTERY . 6. Start the engine of the vehicle that is providing the jump start and turn off electrical accessories . Then start the engine in the vehicle with the discharged battery . 7. Reverse these directions exactly when removing the jumper cables . The negative cable must be disconnected from the engine that was jump started first . MULTI-BATTERY ELECTRONIC JUMP STARTING AID Many RV manufacturers have built into their systems an "emergency start button" on the dashboard that electrically connects the coach batteries to the chassis battery . The purpose of this starting aid is to create an "automatic jump start." The motor home owner should be aware of the possible problems this system may create, such as: Many motor home owners, as a matter of habit, push the "emergency start button" with EACH start under the mistaken belief that three batteries are stronger than one . Without knowing the actual condition of the RV batteries, this action could unknowingly create "dead" or undercharged batteries . If the charge state of the RV battery is LOWER than the chassis battery, then within a few seconds after pushing the start button on the dash both the RV battery and the chassis battery become equal and the motor home owner is then dealing with two or three undercharged batteries . Rapid discharge, to equalize the state of charge between the batteries over a few seconds, is very hard on the batteries . Often, the only "hold back" to this is the connecting wire size . However, if the wires are small enough to slow the rate of discharge to avoid battery damage, then the wires can become overheated from carrying too much amperage . This situation presents a potential electrical failure and/or fire damage. " Each time that the "emergency start button" is pushed, an electrical solenoid switch closes under the hood. Each time this solenoid switch closes, an electric spark arc occurs . Each time this spark arc occurs, a high resistance builds through the copper-to-copper contacts and reduces the overall effectiveness of the switch. In some cases (with severe battery electrical differential) the switch contacts have "stuck" after being used only once. This situation bypasses the isolator and effectively renders the battery isolator system useless . Over the last few years, RV manufacturers have improved these "emergency start button" systems through the use of solid state technology. The application of this solid state technology has appeared to solve the problems associated with the earlier systems . The new system electronically monitors the condition of the RV battery vs. the chassis battery . If the chassis battery has a LOWER state of charge than the RV battery, a light on the dashboard will glow indicating that the "automatic jump start" system has kicked in automatically without the driver physically pushing the button. If the RV batteries are LOWER than the chassis battery, the system will not allow an electrical flow to occur between the batteries . SECTION 7E ENGINE ELECTRICAL SYSTEM GENERATOR (PRE-1987 TYPICAL) ISOLATOR (120 AMP TYPICAL) ACTIVATED INDICATOR (ON INSTRUMENT PANEL) CIRCUIT BREAKER (80 AMP TYPICAL RECOMMENDED) AUXILIARY LOAD AUXILIARY BATTERIES FROM STARTER SWITCH AUXILIARY BATTERIES NOTE: IF AVAILABLE, USE DEEP CYCLE AUXILIARY BATTERIES Figure 7-33- Typical Multi-Battery Electronic Starting Aid Wiring Diagram These fully automatic electronic starting aids allow a current to flow only to the starter motor thereby eliminating battery equalization . This helps to eliminate battery damage and a shortened battery life. A wiring diagram of a typical multi-battery electronic starting aid is shown in Figure 7-33. BATTERY REMOVAL AND REPLACEMENT When handling a battery, the following safety precautions should be observed : 1 . Hydrogen gas is produced by the battery . A flame or spark near the battery may cause the gas to ignite . 2. Battery fluid is highly acidic . Avoid spilling on clothing or other fabric. Any spilled electrolyte should be flushed with large quantities of water and cleaned immediately . To remove or replace a battery, always disconnect the negative cable first, then the positive cable. Torque the battery cables at battery to 9 ft. lbs. NOTE: See Appendix 7-10 at the back of this section of the manual for additional information concerning battery replacement . STARTING (CRANKING) SYSTEM The starter on the motor home chassis requires no maintenance. It will provide years of service if proper cranking procedures are used. When starting an engine, never crank the starter longer than 30 seconds and allow at least 15 seconds between starting attempts . This will help keep the starter from overheating . 7-59 . SECTION 7E ENGINE ELECTRICAL SYSTEM NEUTRAL START SWITCH (WITH AUTOMATIC TRANSMISSIONS) FLYWHEEL Figure 7-34 - Starting Circuit GENERAL DESCRIPTION cirThe function of the starting system is to rotate the engine control circuit activates the solenoid which closes the cuit between the battery and the starting motor. The socrankshaft at sufficient speed for ignition and the start of lenoid also moves the starter drive gear into contact with engine operation . This it does by means of the starting circuit which-consists of the battery, starting motor, ignition the crankshaft ring gear. switch, and the related electrical wiring . In addition, veThree types of starter motors are used. The first, referred hicles with automatic transmissions have a neutral start to as the 10MT series, is shown in Figure 7-35 . The switch which prevents the engine from being started in second type, referred to as the 27MT series, is used on Any transmission selector lever position other than diesel-equipped engines . The main difference is that the NEUTRAL, or PARK. These components are connected 27MT has a center bearing . electrically as shown in Figure 7-34. NOTE: The 1994 454 motor home starter will be a perWhen the ignition switch is turned to START, electrical ' manent magnet type planetary gear reduction current flows from the battery through the key switch, starter designated as PG260. It provides better neutral start switch and through the starter switch to performance quality and reliability in a smaller ground . Inside the starter switch, current flow from this starter motor. SWITCH TERMINAL SOLENOID RISER BARS CONDUCTORS TO RISER BARS TO ARMATURE Figure 7-35 -10MT Starting Motor 7-60 SECTION 7E - ENGINE ELECTRICAL SYSTEM Certain starting motors have the shift lever mechanism and the solenoid plunger enclosed in the drive housing, protecting them from exposure to dirt, icing conditions and splashing . PLUNGER SOLENOID ASSEMBLY In the basic circuit shown in Figure 7-34, the solenoid windings are energized when the switch is closed . The resulting plunger and shift lever movement causes the pinion to engage the engine flywheel ring gear and the solenoid main contacts to close and cranking takes place. When the engine starts, pinion overrun protects the armature from excessive speed until the switch is opened, at which time the return spring causes the pinion to disengage. To prevent excessive overrun, the switch should be opened immediately when the engine starts . The electrical operation of the solenoid is shown in Figure 7-36. The top illustration shows the starter disengaged. The center drawing depicts the pinion partially engaged with the pull-in coil and the hold-in coil activated . The bottom view shows the pinion fully engaged and the starter motor cranking with only the hold-in coil functioning . MAINTENANCE AND INSPECTION DISENGAGED PULL-IN COIL HOLD-IN COIL CURRENT FROM STARTER SWITCH While the starter motor does not require maintenance, the system wiring should be inspected periodically for damage or corrosion . Inspect all connections to the starting motor, solenoid, ignition switch, neutral start switch and battery, including all ground connections . Clean and tighten all connections as required . If there appears to be a problem with the starting system and the battery, wiring and- switches are in satisfactory condition and the engine is known to be functioning properly, refer to the appropriate shop manual for more detailed diagnosis and test procedures . STARTING PROBLEMS (HIGH AMBIENT TEMPERATURES) COMPRESSION SPRING FOR BUTT ENGAGEMENTS PINION PARTIALLY ENGAGED CURRENT FROM BATTERY Under some conditions of high ambient temperatures, when the engine has been turned off and the vehicle allowed to set for 10 to 15 minutes, it is possible to encounter a problem with the starter motor not activating when you attempt to restart the engine . This possibility occurs more frequently with the 7.41- engine when high engine compartment temperatures and the radiated heat from the exhaust pipe cause high resistance in the coil wires of the starter solenoid. This high resistance reduces current flow preventing activation of the solenoid and starter motor. After the engine has cooled down sufficiently, the starter motor should activitate properly upon restart . STARTING PROBLEMS (POOR GROUND) The P-Series motor home is equipped with a webbed ground strap that runs from the rear of the left cylinder head to the frame. To improve electrical contact, remove the strap from both connections . Scrape the (production) paint from both the cylinder head and the vehicle frame, connections . Add a star washer between the cylinder head connection and the strap and between the vehicle frame connection and the strap . Replace the strap and tighten attaching bolts securely . OVER-RUNNING CLUTCH FLYWHEEL PINION FULLY ENGAGED AND STARTER MOTOR CRA NKING Figure 7-36 - Solenoid Electrical Operation 7-61 SECTION 7E ENGINE ELECTRICAL SYSTEM Refer to Appendix 7-12 - "Hot Start" Problem Conditions and Appendix 7-13 - Starter Motor Engagement After Initial Start-Up at the back of this section of the manual for additional corrective procedures. CHARGING SYSTEM GENERAL DESCRIPTION The function of the charging system is to provide electrical power to the engine ignition system, to the vehicle accessories and to restore power lost,, from the battery . The primary component of the system is the generator . The generator assembly includes the rotor, stator and recitifier subassemblies and an integral voltage regulator . When the engine is operating and turning the rotor, an alternating current flow is induced in the stator assembly by the electromagnetic field established in the rotor. The alternating current produced in the stator is changed to the direct current needed in the vehicle's electrical system by the rectifier assembly. This is accomplished through the use of diodes in the rectifier assembly which allow current flow in one direction only. The output of the generator is controlled by the voltage regulator. The voltage regulator does this by varying the strength of the electromagnetic field established in the rotor assembly. The generator is connected to the vehicle electrically as shown in Figure 7-37. The integral regulator is mounted beneath the rear cover of the generator . The brown field wire to the generator is used to initially activate the generator by providing the current needed to establish the electromagnetic field in the rotor. The 10-ohm resistance, provided by either the generator warning lamp or the resistance wire with optional gages, is needed to protect the diodes in the rectifier assembly. GENERATOR SIZING AND SELECTION The base generator, or Delcotron, in the GM motor home is rated 63 to 66 amps . Normally, this rating is large enough for most applications . However, in recent years, the typical RV owner has purchased and/or added on optional electrical equipment pushing base charging system capacity beyond current abilities . A charging system that has demands beyond system ability can create problems, as there is not a way to charge the batteries when the system is always running with an electrical "short fall." The life expectancy of the charging system will be greatly reduced when the system is operating at 100 percent of capacity for extended time. Also engine compartment configurations and optional equipment can aggravate the situation due to restricted air flow and generator overheating . NOTE : If GM factory systems are changed, the size of the main charging wire in the harness must be changed from a 3mm or 12 AWG wire size to an 8mm or 8 AWG wire size. The larger size charging wire is mandatory when installing an upgraded charging system . BATTERY ISOLATOR The battery isolator is a very important link in the total electrical system . Typical isolator hook-ups are shown in Figure 7-37 using broken lines. As shown, the red wire from the battery to the generator is moved to Terminal No. 1 of the battery isolator . A replacement wire connects the generator to Terminal "A" on the battery isolator as shown . A typical RV battery isolator wiring schematic is shown in Figure 7-38. The isolator is equipped with one-way diodes allowing no reverse current flow back to "A" or between Terminal No. 1 or Terminal No. 2. VOLTMETER (GAGE PACKAGE ONLY) GENERATOR WARNING LAMP (EXCEPT GAGE PACKAGE) 10 OHMS RESISTANCE WIRE (RALLY GAGE ONLY) NOTE : BROKEN LINES INDICATE BATTERY ISOLATOR CONNECTIONS GENERATOR Figure 7-37- Charging Circuit - SI System 7-62 SECTION 7E BATTERY 1 VEHICLE GENERATOR ENGINE ELECTRICAL SYSTEM Shown in Figure 7-40 are typical RV battery isolator failure modes. BATTERY 2 AUXILIARY ENGINE RUNNING ISOLATOR TO RUN EQUIPMENT: STEREO, LIGHTS, REFRIGERATOR, ETC . Figure 7-38-Typical RV Battery Isolator Wiring Under "Engine Running," the isolator is internally damaged. Diodes are open or burned out . There is no charging to either battery in this figure. This failure mode could also occur singularly to either outer leg of the isolator. Shown in Figure 7-39 are two typical RV isolator voltmeter checks that will identify a functional isolator. Voltages are based on a reasonable state of charge in all batteries (12 volts) . ENGINE OFF ENGINE OFF The "Engine Off" voltmeter check depicts a normal condition showing that the isolator diodes are functional. ENGINE RUNNING The "Engine Running" voltmeter check depicts a near equal voltage of 13.5 to 13 .8 volts and indicates a normal condition . The generator has switched on and current is passing through both sides of the isolator. You are not checking the generator amperage capacity, only the isolator function . If no charge voltage is reaching one or the other batteries, check for a failed fusible link or circuit breaker installed in either or both charging wires. Shown under "Engine Off," the isolator is wired incorrectly externally or internally . Voltage should not be supplied to terminal '.'A" with the engine off. Check the source of the problem by removing the wire from the "A" terminal . The wire should not have any voltage and the isolator should not have any voltage either . Figure 7-40 - Typical RV Battery Isolator Failure Modes Three prime rules that must be followed for isolators are : Each leg of the isolator must be sized to equal or exceed the total generator output. The reason is that one battery may require all of generator's output while the other(s) require none . Thus a single leg must be capable of carrying the maximum generator current output. Isolators should be purchased oversized if there is any chance of upgrading the generator at a later date. NOTE: A voltage drop of about 1/2 volt to "1 " and "2" would be a normal drop through the diodes . Figure 7-39-Typical RV Isolator Voltmeter Checks 7-63 SECTION 7E - ENGINE ELECTRICAL SYSTEM GENERATOR RATED OUTPUT IN AMPS Up 70 95 120 to 70 amp to 95 amp to 120 amp to 160 amp MINIMUM CHARGING WIRE SIZE FOR WIRE LENGTH IN FEET UP TO 10 FEET 11 FEET TO 14 FEET 15 FEET TO 20 FEET 21 FEET TO 25 FEET 26 FEET TO 30 FEET 10 6 4 4 8 6 4 4 8 4 4 2 6 4 2 2 6 4 1 0 Figure 7-41- Charging Wire Size to Output 2. In the auxiliary battery side, a circuit breaker or fusible link should be included. A fusible link on the automotive side will be standard as produced by GM . 3. The size of the charging wire should be chosen using the chart shown in Figure 7-41 . CHARGING SYSTEM -1987 TO CURRENT With the start of 1987 production, the CS130 105 AMP Delcotron generator was provided as standard equipment on all P-30 motor home chassis . The CS series generator is unique in that it requires voltage to both the excitor terminal and the positive outpost in order to charge . Solid state isolators are designed to prevent feedback of current from batteries to the generator. This requires that the isolator be redesigned to include a fourth terminal called an excitor terminal . This fourth terminal is connected to the ignition switch . The ignition switch provides current when in the "RUN" position to the excitor terminal on the isolator . Current is allowed to flow from the "E" terminal via a diode to the "A" terminal providing the necessary current allowing the generator to charge. Refer to Figure 7-42 for typical wiring of the solid state isolator and CS Series Delcotron generator . GENERATOR BATTERY 1 VEHICLE BATTERY 2 AUXILLIARY TO RUN EQUIPMENT : STEREO, LIGHTS, REFRIGERATOR, ETC . Figure 7-42 - Typical CS Series Delcotron Generator and Solid State Isolator Wiring 7-64 SECTION 7E ENGINE ELECTRICAL SYSTEM CS SERIES GENERATOR AND ISOLATOR DIAGNOSIS A preliminary check of a "no charge" condition should be made to ensure that voltage is provided to both the excitor ("F" terminal) and the positive output post (B+) on the generator when the ignition is on . If voltage is not present on either terminal, the generator will not charge . See Figure 7-43. 1987 TO CURRENT CS130 DELCOTRON GENERATOR 105 AND SOLID STATE ISOLATOR KEY OFF VOLTS KEY ON ENGINE NOT RUNNING SOLID STATE ISOLATOR If voltage is not present at the generator excitor terminar with the ignition key "ON" check the fuses and wiring . Repair as necessary . If battery voltage is not present at the generator output terminal, check the wiring and connections. Repair as necessary . If the vehicle is equipped with a solid state battery isolator, check for voltage at the isolator excitor terminal with the ignition key in the "RUN" position . If voltage is not present, check the fuse and wiring . Repair as necessary. NOTE : When the vehicle is equipped with a solid state isolator and if the coach battery is discharged below 9 volts, excessive current will flow from the chassis battery through the excitor terminal to the low battery and can cause the excitor fuse to "blow" causing a "no charge" condition . This occurs when the key is turned to the "RUN" position prior to starting the engine. If voltage is present at the "E" terminal but not on the "A" terminal, the isolator is defective and will require replacement . ELECTROMECHANICAL ISOLATOR The electromechanical circuit as shown in Figure 7-44 can be used for battery isolation on all 1987 to current motor chassis equipped with a CS Series generator. A KEY ON ENGINE RUNNING If isolator voltage checks result in the above readings, the charging system is functioning normally . Figure 7-43 - Typical Solid State Isolator Voltage Checks MAINTENANCE AND INSPECTION No periodic adjustments or maintenance of any kind are required on the entire generator assembly. However, belt tension should be checked periodically and adjusted as required . See Appendix 7-14 - Generator Belt Usage on 6.2L Diesel Engines at the back of this section, as well as the manual Appendix A - Drive Belts and Tension Specifications located at the back of the manual for additional information concerning belt tension specifications . Noise from a generator may be caused by a loose drive pulley or loose mounting bolts. These parts should be tightened as required . Other causes of generator noise can be worn or dirty bearings, defective diode(s) or a defective stator. Such causes require an overhaul . SECTION 7E - ENGINE ELECTRICAL SYSTEM IGNITION FUSED DELCOTRON "P" TERMINAL ' NORMALLY OPEN RELAY GM PART NO. 14089936 NOTE : THE RELAY IDENTIFIED MUST BE USED AS THE VOLTAGE ON THE "P" TERMINAL IS LESS THAN 12 VOLTS . CHASSIS BATTERY DELCOTRON "I" TERMINAL DELCOTRON "B + " POST I NORMALLY OPEN MAGNETIC SWITCH GM PART NO. 15555675 AUXILIARY BATTERY Figure 7-44 - CS130 Magnetic Switch/Battery Installation Wiring Diagram IGNITION SYSTEM GENERAL DESCRIPTION The ignition circuit consists of the battery, the distributor, the ignition switch, the spark plugs and the primary and secondary wiring . Electrical current to power the ignition system is provided by the battery during starting and by the charging system when the engine is operating . This low-voltage current flows through the ignition switch, the electronic module in the distributor and the coil in what is called the primary circuit . In the coil, the low-voltage current is changed to a high-voltage current each time the primary circuit is switched off and on by the electronic module . The module breaks the circuit in response to signals from the magnetic pickup assembly. These signals are timed with the power stroke of each cylinder . The high-voltage current generated in the second part of the coil, flows to the center terminal of the distributor cap through the rotor, to each outer terminal of the distributor cap in rotation . From each distributor cap outer terminal, the current flows through the wire to the spark plug. At the spark plug, the current jumps the gap between the electrodes to ground, producing the spark for ignition . This high-voltage circuit is referred to as the secondary circuit . H .E.I. DISTRIBUTOR The High Energy Ignition (H.E .I.) distributor used on the 5.7L and the Mark IV engines, combines all ignition components in one unit (Figure 7-45) . It is located on top of the engine block directly behind the carburetor. The external electrical connections (Figure 7-46) are the ignition switch feed wire, the tachometer pickup and eight spark plug leads . The ignition switch feed connector to the distributor has full battery voltage when the ignition switch is in the "RUN" and "START" positions . THERE IS NO RESISTOR WIRE FROM THE IGNITION SWITCH TO THE DISTRIBUTOR. The ignition coil is in the distributor cap and connects through a resistance brush to the rotor . The High Energy Ignition system is basically identical in operation to conventional ignition systems except that the module and pickup coil replace the contact points . The High Energy Ignition is a magnetic-pulse-triggered, transistor-controlled, inductive discharge ignition system. The magnetic pickup assembly located inside the distributor contains a permanent magnet, a pole piece with internal teeth, and a pickup coil . When the teeth of the timer core rotating inside the pole piece line up with the teeth of the pole piece, an induced voltage in the pickup coil signals the electronic module to trigger the coil primary circuit . SECTION 7E ENGINE ELECTRICAL SYST EM CONNECTOR COIL (GM PART NO . 1875894) B+ TERMINAL BAT. TERMINAL (CONNECTED TO IGNITION SWITCH) SEAL TACH I TERMINAL CAP (GM PART NO . 10475118 ROTOR (GM PART NO. 10470600 CONNECT TACHOMETER FROM THIS TERMINAL TO GROUND . NOTE : HOLD DOWN BRACKET POSITIONED ON THIS FLANGE SECURES DISTRIBUTOR TO ENGINE BLOCK. (SOME TACHOMETERS MUST CONNECT FROM THIS TERMINAL TO ENERGIZE POSITIVE [+1. CONSULT TACHOMETER MANUFACTURER.) NOTE : CHISEL MARK ON SOME PRODUCTION ENGINE DISTRIBUTOR FLANGES TO MANIFOLD SHOWS TIMING AS PRODUCED BY PLANT. VACUUM UNIT CONNECTOR Figure 7-46 - H.E .I . Distributor Assembly Electrical Connections * NOTE : LATER PRODUCTION ROTOR IS OFF-WHITE IN COLOR - WITH HIGHER DIELECTRIC STRENGTH SECONDARY WIRING Figure 7-45 - H.E.I . Distributor - Exploded View The primary current decreases and a high voltage is induced in the ignition coil secondary winding which is directed through the rotor and secondary leads to fire the spark plugs. The capacitor in the distributor is for radio noise suppression. The magnetic pickup assembly (Figure 7-47) is mounted over the main bearing on the distributor housing and is made to rotate by the vacuum control unit, thus providing vacuum advance. The timer core is made to rotate about the shaft by conventional advance weights, thus providing centrifugal advance. The module automatically controls the dwell period, stretching it with increasing engine speed. The H.E .I . system also features a longer spark duration, made possible by the higher amount of energy stored in the coil primary winding. This is desirable for firing lean mixtures . The spark plug wire used with the H.E .I . system is a carbon-impregnated cord conductor encased in an 8mm diameter silicone rubber jacket . The silicone wiring will withstand very high temperatures and also provides an excellent insulator for the higher voltage of the H .E .I . system . Th e silicone spark plug boots form a tight seal on the plug . SPARK PLUGS Resistor-type, tapered-seat spark plugs with a 14mm thread diameter are used on the 5.71- and Mark IV gasoline engines. (See figure 7-48 .) A gasket is not used on these tapered-seat plugs. The recommended torque specification for installing the plugs in these engines is 17-27 ft . lbs. Normal or average service is assumed to be a mixture of idling, slow-speed and high-speed operation with some of each making up the daily total driving. Occasional or intermittent high-speed driving is essential to good spark plug performance as it provides increased and sustained combustion heat that burns away any excess deposits of carbon or oxide that may have accumulated from frequent idling or continual stop-and-go or slow-speed driving. 7-67 SECTION 7E ENGINE ELECTRICAL SYSTEM ELECTRONIC MODULE - NON FUEL INJECTED ENGINES (GM PART NO. 1875990) FUEL INJECTED ENGINES 350-454 (GM PART NO. 10496048) DISTRIBUTOR BASE POLE PIECE (GM PART NO. 1875981) now FI (GM PART NO. 10495801) with FI SHAFT VACUUM CONTROL UNIT CAPACITOR (SOME MODELS) Figure 7-47- H.E.I. Magnetic Pickup Assembly ENGINE 350 CID 454 CID 1983-1984 R45T R44T INSTALLATION TORQUE 17-27 FT. LB. GAP .045 GAP Figure 7-48 - Spark Plug AC PART NO. 1985-1989 CR43TS R44T 1990-1994 *R43TS Spark plugs are protected by an insulating nipple made of special heat-resistant material which covers the spark plug terminal and extends downward over a portion of the plug insulator . These nipples prevent flash-over with resultant missing of engine, even though a film is allowed to accumulate on the exposed portion of plug porcelains. Do not mistake corona discharge for flash-over or a shorted insulator . Corona is a steady blue light appearing around an insulator, just above the shell crimp. It is the visible evidence of high-tension field and has no effect on ignition performance. Usually it can be detected only in darkness. This discharge may repel dust particles, leaving a clean ring on the insulator just above the shell . This ring is sometimes mistakenly regarded as evidence that combustion gases have blown out between the shell and insulator . SECTION 7E ENGINE ELECTRICAL SYSTEM If it should become necessary to remove and replace the spark plugs, do not substitute a spark plug having a different heat range in order to compensate for a performance complaint . A spark plug of the proper heat range and one that is properly gapped will not cause a driveability problem. If spark plugs are installed that have a higher heat range than called for, the valves can become "tuliped" or the pistons can become pitted, eroded and burned through . On the other hand, if spark plugs with a lower than called for heat range are installed, plug fouling and bad emissions will usually result. WATER PUMP TIMING POINTER ALTERNATE POSITION (LOWER SIDE) Note: View with timing light from underside of vehicle . NOTE: Generally, spark plugs containing the suffix TS or CTS can be used interchangeably . (See Figure 7-48 .) However, during the 1986 model year, AC Spark Plug changed the center electrodes in their spark plugs to copper. For these plugs, the letter C may be removed from the identification number on the jacket . EXAMPLE : A spark plug with a code identification of Re43TS or R43CTS would be changed to *R43TS . IGNITION TIMING TIMING POINTER (UPPER SIDE) Note: View with timing light from top of engine . Figure 7-49 - Timing Mark - Typical To assure optimum engine performance, the ignition must be properly timed . This means that the spark plug must fire at precisely the instant when the fuel mixture is correct and cylinder compression is highest . 5 . Turn off the engine and remove the timing light. Reconnect the number 1 spark plug wire, if removed . Set the ignition timing by following these instructions : 1 . Refer to the Vehicle Emission Control Information Label located on the radiator support panel. Follow all instructions on the label . . MAINTENANCE AND INSPECTION 2. With ignition off, connect the pickup lead of the timing light to the number 1 spark plug wire (engines with the timing pointer mounted over the upper side of the damper), or to the number 5 or 8 spark plug wire (engines with the timing pointer mounted at the lower left side of the damper) . Use a jumper lead between the wire and plug or an inductive-type pickup . DO NOT pierce the wire or attempt to insert a wire between the boot and the wire. Connect the timing light power leads according to manufacturer's instructions . 3. Disconnect and plug the vacuum line at the distributor . H.E.I. DISTRIBUTOR No periodic lubrication is required . Engine oil lubricates the lower bushing and an oil-filled reservoir provides lubrication for the upper bushing . H.E.I. TEST PROCEDURE If there appears to be a problem with the ignition system, the following procedure can be used as a quick-check in determining the cause . More detailed procedures are given in the appropriate shop manual . 4. Start the engine and aim the timing light at the timing . General Test mark. (See Figure 7-49 .) The line on the balancer or 1 . Remove a spark plug wire from each spark plug one pulley will line up at the timing mark. If a change is at a time and check for spark using an H .E.I . Test Spark necessary, loosen the distributor hold-down clamp bolt Plug ST125 (GM Part No. 5613602) or equivalent . If at the base of the distributor. While observing the mark spark is present, the H.E.I. system is O.K . with the timing light, slightly rotate the distributor until the line indicates the correct timing . Tighten the holddown bolt and recheck the timing . NOTE: Using the Test Spark Plug to check for spark instead of allowing the spark to jump to ground On a motor home chassis with the engine having the from the disconnected wire can help to avoid pos timing pointer mounted at the lower left side of the sible damage to the module . A Test Spark Plug damper, the timing light must be aimed up from beshould be available at a local auto parts store. neath the vehicle . This procedure require,$ two people, one to observe the mark with the timing light while the second person makes any required adjustments at the 2. Connect a test light between the distributor TACH terdistributor. minal and ground. 7-69 SECTION 7E - ENGINE ELECTRICAL SYSTEM 3. Turn on the ignition switch. PUT VASELINE ON BLADE TERMINALS " If the light does not glow, check for power at the distributor BAT terminal . If there is no power at the BAT terminal, the problem is in the circuit wiring or the ignition switch. Repair as required . If there is power at the BAT terminal, and no power at the TACH terminal, the ignition coil primary winding is open . Replace the coil. CONNECTOR REMOVED WHITE WIRE " If the light glows, crank the engine . The light should glow intermittently, indicating that the module and pickup coil are working . Remove the distributor cap and check for spark at the center terminal of the cap using the H.E.I. Test Spark Plug and a jumper wire. If there is spark, the rotor is not functioning and should be replaced . If there is no spark, the coil is not functioning and should be replaced . (SOLDER CLIP TO WIRE) If the light glows steadily while the engine is being cranked, perform the module test. NOTE: REFER TO GM SERVICE BULLETIN NO. 78-1-59 DATED OCTOBER, 1978 Module Test 1 . Remove the distributor cap and connect the H .E.I . Test Spark Plug to the center terminal with a jumper wire. Figure 7-50- Module Connections 2. Remove the pickup coil connector from the module and turn the ignition switch on. loose. Reflow the existing solder, and add solder if necessary to assure good connections . Avoid excess solder . Use a small iron or gun . Do not allow heat to damage the insulation or solder to run under the terminal. Squeeze the side rails of the terminals with needle-nose pliers to assure a tight fit on the module terminals . 3. Touch one end of another jumper wire to the positive terminal of the battery and the other end to the small terminal of the module momentarily . As the jumper wire is removed from the module terminal, if there is : " a spark - the pickup coil is not functioning properly and may need to be replaced . " no spark - the module is not functioning properly and may need to be replaced . CHECKING H .E.I. SYSTEM CONNECTIONS (SQUEEZE COIL TERMINALS) 3. Apply a thin coating of petroleum jelly (i .e., Vaseline) on all module terminals to reduce future oxidation . Make sure a small amount of silicone heat transfer grease (AC-Delco D-1920 or equivalent) is present on the module base. Apply the grease if necessary. If a component appears to be inoperative, the condition may actually be due to poor connections . This is especially true of low-voltage circuits, such as the pickup coil to module connections in the H.E.I . system . 4. Reinstall the module on the H.E.I. base and reconnect the leads making sure all terminals are seated with good metal-to-metal contact . Before any component or assembly is considered faulty and replaced, its terminal(s) should be cleaned, the connector-to-terminal fit tightened and the wire-to-terminal connection checked and resoldered if necessary. SPARK PLUG WIRES The following procedure covers one example involving H .E.I. low-voltage circuits where good connections are essential . Refer to Figure 7-50. 1 . Remove the module and clean the terminals with emery cloth or a wire brush to remove any oxide film. 2. Remove the connector body (if so equipped) from the pickup coil leads . Carefully inspect the terminal-to-wire connections (green and white leads) and recrimp if Use care when removing spark plug wire boots from spark plugs. Twist the boot 1/2 turn before removing, and pull on the boot only to remove the wire. Borroughs Tool No. BT-7901 B or-equivalent will make the removal of the spark plug wires easier. (See Figure 7-51 .) It is extremely important when replacing plug wires to route the wires correctly and through the proper retainers . Failure to route the wires properly can lead to radio ignition noise and crossfiring of the plugs, or shorting of the leads to ground . 7-7 0 SECTION 7E ENGINE ELECTRICAL SYSTEM bon deposits . The black deposits are usually the result of slow-speed driving and short runs where sufficient engine operating temperature is seldom reached. Worn pistons, rings, faulty ignition, over-rich carburetion and spark plugs which are too cold will also result in carbon deposits. Excessive gap wear, on plugs of low mileage, usually indicates the engine is operating at high speeds or with loads that are consistently greater than normal or that a plug which is too hot is being used . In addition, electrode wear may be the result of plug overheating, caused by combustion gases leaking past the threads, due to insufficient torquing of the spark plug. Excessively lean carburetion will also result in excessive electrode wear. BORROUGHS TOOL NO . BT-7901 B HEAT TREATED SPRING STEEL CONSTRUCTION FOR LONG LIFE Broken insulators are usually the result of improper installation or carelessness when regapping the plug. Broken upper insulators usually result from a poor-fitting wrench or an outside blow . The cracked insulator may not make itself evident immediately, but will as soon as oil or moisture penetrates the fracture . The fracture is usually just below the crimped part of the shell and may not be visible . Phone No. 1-800-253-0138 Figure 7-51 -Spark Plug Boot Puller Broken lower insulators usually result from carelessness when regapping and generally are visible . In rare instances, this type of break may result from the plug operating too "hot," encountered in sustained periods of high-speed operation or under extremely heavy loads. When regapping a spark plug, to avoid lower insulator breakage, always make the gap adjustment by bending the ground (side) electrode . Spark plugs with broken insulators should always be replaced . 6:21 DIESEL GLOW PLUG ELECTRICAL SYSTEM GENERAL DESCRIPTION In the diesel engine, air alone is compressed in the cylinder ; then after the air has been compressed, a charge of fuel is sprayed into the cylinder and ignition occurs due to the heat of compression . Eight glow plugs are used to preheat the chamber as an aid to starting. Figure 52-Spark Plug Shield for 7.41Cyl . 1 thru 6 & 8 10089660 2-518 inch Cyl . 7 10089661 1-7/8 inch Plug Wire Set 85-86 H4D 12043750 85-89 H5D 12072181 90-93 H5D 12074045 The glow plugs are heaters that turn on when the ignition key is turned to the run position prior to starting the engine . They remain pulsing a short time after starting, then automatically turn off. SPARK PLUGS Worn or dirty plugs may give satisfactory operation at idling speed, but under operating conditions they frequently fail . Faulty plugs are indicated in a number of ways: poor fuel economy, power loss, loss of speed, hard starting and general poor engine performance. Spark plug failure, in addition to normal wear, may be due to carbon fouled plugs, excessive gap or broken insulator . (See Figure 7-48 .) Fouled plugs may be indicated by checking for black car7-71 SYSTEM COMPONENTS The 6 .2-liter diesel glow plug control system consists of a thermal controller, glow plug relay, 6-volt glow plugs and a "glow plugs" lamp. (See Figure 7-53) Other components which have no function in controlling glow plug operation but are part of the electrical system, start-and-run "operations are : fuel solenoid, fast idle and cold advance solenoids, cold advance temperature switch and the TCC, EGR (if equipped) and EPR solenoids . The electrical operation and diagnosis of the fuel solenoid, fast idle and cold advance solenoid and the cold advance temperature switch will be covered briefly here . SECTION 7E ENGINE ELECTRICAL SYSTEM GLOW PLUG INHIBIT TEMP SWITCH GM PART NO . 15599010 GLOW PLUG CONTROLLER GM PART NO. 12040822 Figure 7-53 - Electronic Glow Plug Control System 1985 and Forward Controller The thermal controller is mounted in the water passage at the rear of the engine. Thermostatic, elements within the controller are designed to open or close the ground circuit to the glow plug relay as necessary to control the preheat and afterglow cycles of glow plug operation . Glow Plug Relay The glow plug relay provides current to the glow plugs . The relay is pulsed on and off by the thermal controller. NOTE: Do not bypass the glow plug relay. This relay is automatically controlled . Any attempt to bypass the relay with a jumper wire or rewire for manual control, may result in glow plug failure . Glow Plugs The glow plugs used in this system are 6-volt plugs which are operated at electrical system voltage (12 volts) . The plugs are a "fast start" design capable of reaching 1,800°F in 7.5 to 9 seconds when the engine temperature is 0°F. They are not designed to burn continuously and are pulsed on and off as needed, by the thermal controller. "Glow Plugs" Lamp The "glow plugs" lamp is mounted in the instrument cluster. The lamp is wired across the glow plugs and is illuminated whenever the glow plugs are heated. Fuel Solenoid The fuel solenoid is activated whenever the ignition switch is on. The solenoid is located in the fuel injection pump housing cover . Cold Advance Solenoid The cold advance solenoid, also located in the injection pump cover, is controlled by a cold advance temperature switch which activates this solenoid and the fast idle solenoid at a specified minimum temperature . The switch should be closed below 90°F and open above 122°F. Instrumentation Vehicles with the diesel engine. have special instrumentation indicators to permit the operator to properly apply the starting procedure . A "glow plugs" light on the instrument panel provides this information on the engine starting conditions . 7-72 SECTION 7E - ENGINE ELECTRICAL SYSTEM NOTE : TERMINAL "5", BLK . GRD . SPLICES INTO TERMINAL "W', BLK, AT SPLICE 150. THEY THEN GRD . A T ENG . FAST IDLE & COLD ADVANCE TEMP. SW. OPENS AT 95OF 10 OHMS vUESI W/vA 150 NOTE : THE T .C .C . SOL . SWITC H WILL OPEN AT W .O .T . ONLY WHEN THE SWITCH IS NOT ATTACHED TO THE INJ . PUMP Figure 7-54 - Diesel Glow Plug Wiring Diagram 198285 Also these vehicles have a "water-in-fuel" lamp and "low engine coolant" lamp . Modifications Required for Diesel Starting BATTERY - The diesel engine uses dual batteries to provide the extra power required to operate the glow plugs and the larger starter used on this engine . A standard generator supplies charging current to both batteries at the same time . There are no switches or relays in the charging circuit. STARTER - The starter is larger and designed to crank the engine to at least the 100 RPM required for starting . Circuit Operation - Cold Start (See Figure 7-54) With the ignition switch in "RUN,'' the following events take place simultaneously : 1 . The fuel solenoid is energized and opens the fuel metering valve. The fuel heater is powered, provided the temperature is low enough to require heating of the fuel . 2 . Battery voltage is applied to the fast idle solenoid and cold advance solenoid through the fast idle/cold advance temperature switch (when closed) . 3. Battery current flows through the thermal controller circuits and through the glow plug relay coil to ground . 4. The glow plug lamp, which is wired across the glow plugs, comes on whenever the glow plugs are powered . 5. The thermal controller starts the glow plug's heating cycle. Initially, the glow plugs are activated continuously for a period of 7.5 to 9 seconds at 0°F (Figure 7-55). The glow plugs then begin to pulse on and off at a rate determined by the thermal characteristics of the controller.The initial current brings the glow plug preheat chamber up to the temperature required forcold starting .The pulsecycle(on and off)acts to maintain chamber temperature to provide stable engine warm-up. As the engine warms up, the ther- 7-73 SECTION 7E - ENGINE ELECTRICAL SYSTEM mal controller turns off all current to the relay, deenergizing the glow plugs completely . The controller is capable of varying glow plug operation as required (up to one minute) when the engine is started warm, and little or no heating is necessary. GLOW PLUG TEST Controller failure, as in the case of prolonged preheat (more than 9 seconds), would cause a circuit breaker in the controller to open, cutting off glow plug operation completely . Using an ohmmeter, adjusted to a low-range scale, check for continuity between the terminal and body of each plug as shown in Figure 7-56. The ohmmeter reading should be approximately 0.5 ohm . If the reading is infinity, the glow plug coil is burned out or faulty and the plug should be replaced. This test can be performed with the plugs either installed or removed from the engine. If the plugs are installed, the engine should be off and the feed wire disconnected from each plug . "FAST START" SYSTEM 2,000 °F GLOW PLUG TEMPERATURE ENGINE READY TO CRANK PRE-CHAMBER WARM UP TIME 7 .5 TO 9 SEC . Figure 7-55 - Glow Plug Control MAINTENANCE AND INSPECTION No routine service is required for the diesel glow plug electrical system . However, should there be a problem with the system, it is wise to first inspect the system to ensure that all connectors are installed properly and that all connections are clean and tight. The glow plugs can be checked for continuity with the procedure in this section. If the inspection and checks do not reveal the problem, refer to the shop manual for the diagnosis procedure . Figure 7-56 - Glow Plug Test APPENDIX 7-10 BATTERY SIZE AND CRANKING vs. TEMPERATURE The following information is provided as an aid to the motor home owner in understanding battery size and cranking capacity in relation to temperature . The chart shown in Figure A7-10-1 explains why a battery of sufficient electrical size is essential if satisfactory cranking of the engine is to be achieved at low temperatures . At temperatures below zero, the capacity of the battery at full charge is about 30 percent of rated capacity at 80°F. At the same time, the load imposed on the battery by the engine is about 3-1/2 times the normal cranking load at 80°F. In effect, at lower temperatures the battery would seem "smaller" while the engine would appear to be "larger," as depicted in the figure . The charts below (Figure A7-10-2) provide an example of the "shrinking" battery in terms of Cold Cranking Amps (CCA) in relation to temperature . Just as low winter temperatures can create cold-start Figure A7-10-1- Battery Cranking vs. Temperature cranking problems due to the electrical size and cranking capacity of a battery, the majority of winter engine failures For best fuel economy and cold starting protection to enare skuff and bearing seizures that occur upon initial start- gine surfaces, consider the range of temperature your up. The reason for these problems is oil starvation from vehicle will be operated in during the next oil change . drain-off and the fact that the oil is too thick to pump quickly Then, select the recommended oil viscosity from the apto the bearing surfaces. plicable chart shown in Figure A7-10-3. 100% FULL-CHARGED BATTERY BASE BATTERY HD BATTERY 405 CCA 650 CCA 80 DEGREES = 100% 880 CCA 1413 CCA 32 DEGREES = 68% 598 CCA 960 CCA 0 DEGREES = 46% 405 CCA 650 CCA -20 DEGREES = 30% 264 CCA 423 CCA 65% CHARGED BATTERY - GREEN EYE VISABLE BASE BATTERY HD BATTERY 405 CCA 650 CCA 80 DEGREES = 100% 572 CCA 918 CCA 32 DEGREES = 68% 389 CCA 624 CCA 0 DEGREES = 46% 263 CCA 422 CCA -20 DEGREES = 30% 171 CCA 275 CCA ' Figure A7-10-2 - Cold Cranking Amps vs. Temperature 7-75 APPENDIX 7" f0 BATTERY SIZE AND CRANKING vs. TEMPERATURE (Cont'd) Hot Weather Hot Weather of +100 +60 +40 +32 +20 +10 0 -20 SAE 30 SAE 20W-20 ---® SAE 15W-40 SAE IOW-30 PREFERRED Cold Weather Cold Weather GASOLINE ENGINES DIESEL ENGINES Figure A7-10-3 - Gasoline and Diesel Engine Oil Viscosity Charts NOTE: THE GM MAINTENANCE SCHEDULE RECOMMENDS INSPECTION OF ALL ENGINE DRIVE BELTS AT EACH OIL CHANGE . DRIVE BELTS SHOULD BE INSPECTED FOR CRACKS, FRAYING AND WEAR . DRIVE BELTS SHOULD BE ADJUSTED OR REPLACED AS NEEDED. SEE APPENDIX A DRIVE BELTS AND TENSION SPECIFICATIONS AT THE BACK OF THIS MANUAL FOR ADDITIONAL INFORMATION . APPENDIX 7-10 BATTERY SIZE AND CRANKING vs. TEMPERATURE (Cont'd) NOTE- The following charts are provided to aid service personnel and the motor home owner for proper engine electrical diagnosis . SLOW CRANKING, SOLENOID CLICKS OR CHATTERS CHECK: BATTERY FOR GREEN INDICATOR. VISUAL CONDITION OF BATTERY CABLES AND CONNECTIONS. IF BATTERY NEEDS CHARGING, MAKE GENERATOR AND BATTERY DRAIN CHECK, CHARGE BATTERY AND RECHECK CRANKING . IF TROUBLE HAS NOT BEEN FOUND, PROCEED. REMOVE BATTERY LEAD FROM DISTRIBUTOR ON H.E .I . MAKE ALL VOLTMETER READINGS WITH KEY IN START POSITION . MEASURE CRANKING VOLTAGE AT BATTERY TERMINAL POSTS . 9.6 VOLTS OR MORE LESS THAN 9.6 VOLTS MEASURE VOLTAGE FROM BATTERY NEGATIVE TERMINAL TO ENGINE BLOCK. (POS. LEAD ON BLOCK.) CHECK BATTERY CONDITION AND CAPACITY REPAIR GROUND CABLE AND CONNECTIONS MEASURE VOLTAGE AT SOLENOID "B" TERMINAL, CLEAN AND TIGHTEN CONNECTIONS AT STARTER CLEAN AND TIGHTEN POSITIVE CABLE CONNECTIONS. IF O.K ., REPLACE CABLE. NOTE : THIS PROCEDURE IS DESIGNED FOR USE ON ENGINES AND BATTERIES AT ROOM OR NORMAL OPERATING TEMPERATURES. IT ALSO ASSUMES THERE ARE NO ENGINE DEFECTS WHICH WOULD CAUSE CRANKING PROBLEMS. TO USE IT UNDER OTHER CONDITIONS MIGHT RESULT IN MISDIAGNOSIS. Figure A7-10-4 - Slow Cranking - Diagnosis Chart ' 7-77 APPENDIX 7-10 BATTERY SIZE AND CRANKING vs. TEMPERATURE (Cont'd) NO CRANKING, NO SOUND FROM SOLENOID TURN HEADLIGHTS AND DOME LIGHT ON . TURN KEY TO START LIGHTS STAY BRIGHT LIGHTS DIM OR GO OUT L CHECK BATTERY STATE-OF-CHARGE GREEN EYE SHOWING LESS THAN 9.6 VOLTS CHECKVOLTAGE FROM ENGINE BLOCK TO BATT. NEG. POST. KEY IN START POSITION, (POS. LEAD ON BLOCK). 5 VOLT OR MORE LESS THAN .5 VOLT CLEAN AND TIGHTEN GROUND CABLE CONN . AND/OR REPLACE CABLE CHECK CRANKING VOLTAGE AT STARTER "B" TERMINAL LESS THAN 9 VOLTS CLEAN AND TIGHTEN POS. BATTERY CABLE TERMINALS AND/OR REPLACE CABLE . CARS WITHOUT NEU. ST. SW. f CARS WITH NEU. ST. SW. CHECK VOLTAGE AT EACH NEUTRAL START SWITCH TERMINAL (AUTO. TRANS. I N PARK, MAN. TRANS. CLUTCH DEPRESSED, KEY IN START) . 9.6 VOLTS OR MORE TEST BATTERY: IF O.K ., REPAIR STARTER DON'T OPERATE OPERATE O.K . EYE DARK CHECK CRANKING VOLTAGE AT BATTERY POSTS. TURN ON RADIO, HEATER AND TURN SIGNALS CHECK BULKHEAD CONNECTOR, FUSEABLE LINE AND IGNITION SWITCH CONNECTIONS. LESS THAN 7 VOLTS ON ONE TERM . CHECK CONNECTIONS AND VOLTAGE AT SOLENOID "B" TERM . 9 VOLTS OR MORE CHECK NEUTRAL START SWITCH ADJUSTMENT AND CONNECTOR; IF O.K ., REPLACE SWITCH WITH KEY IN START, CHECK VOLTAGE AT IGNITION SWITCH SOLENOID TERM . CHECK FUSEABLE LINK AND BULKHEAD CONNECTOR. REPAIR STARTER Figure A7-10-5 - No Cranking - Diagnosis Chart 7-78 7 VOLTS OR MORE LESS THAN 7 VOLTS REPAIR PURPLE WIRE FROM IGNITION SWITCH REPLACE IGNITION SWITCH APPENDIX 7- 11 ADD-ON (AUXILIARY) ELECTRICAL EQUIPMENT INSTALLATIONS The following information has been extracted from a Chevrolet Dealer Service Technical Bulletin relating to add-on (auxiliary) electrical equipment installations for vehicles with side terminal batteries . make use of the existing battery cables . If the battery requires relocation and longer cables are required, a proportionately larger gauge wire must be used. If in relocating the battery, the negative ground cable is attached to the frame rail, a cable of similar gauge must be provided between the frame rail and the engine. This is required due to the heavy electrical loads imposed by the starting circuit . Reference : Chevrolet Dealer Service Technical Bulletin No. 85-17 (December, 1984) The use of electronics on today's vehicles require that both power and ground connections for add-on (auxiliary) electrical equipment (mobile radios, light bars, etc .) be made at the battery . The Side Terminal Adaptor Package (GM Part No. 1846855) when combined with the longer battery bolt (GM Part No. 12004188) and spacer (GM Part No. 12004189) will provide and maintain corrosion resistance and the electrical integrity designed into the Delco side terminal battery . (See Figure A7-11-1 .) GM recommends that all service personnel and motor home owners involved in add-on (auxiliary) electrical equipment installations perform the following procedures. To ensure proper operation of the battery cables, the following chart on length, gauge and materials must be adhered to : CABLE GAUGE 4 2 0 COMBINED LENGTH OF POSITIVE AND NEGATIVE CABLE IN INCHES COPPER COPPER CLAD ALUMINUM 66 107 170 52 67 111 , Figure A7-11-2- Add-On Electrical EquipmentWire Gauge and Materials Specifications The vehicle battery should -be located and positioned to ADD-ON (AUXILIARY) EQUIPMENT CABLE(S) VEHICLE BATTERY CABLE CONTACT SPACER GM PART NO. 12004189 ADAPTER TERMINAL* LONG BATTERY TERMINAL BOLT GM PART NO. 12004188 TERMINAL COVER' Figure A7-11-1-Add-On Electrical Equipment-Typical Installation 7-79 VEHICLE BATTERY 'PART OF TERMINAL ADAPTER PACKAGE, GM PART NO. 1846855 . ALSO SOLD SEPARATELY BY DELCO (PART NO. 7450 - 10 TO A BOX) APPENDIX 7" 12 "HOT START" PROBLEM CONDITIONS control circuit/connection resistance, or a defective solenoid . First item to check when hot start (hot soak) is the ground cable - LH frame rail to LH cylinder head. Poor ground give high resistance when hot . Remove bolts and clean - be sure the star washer is used to insure good ground . The following information has been extracted from three GM Service Bulletins relating to "hot start" problems. The information begins with a discussion of the simple basics of loose connections, proceeds to the addition of heat shields and finally to adding a magnetic switch. Problem conditions and corrective procedures are described . If no troubles are found, a new starter solenoid package, PIN 10457024, is available to repair the vehicle . This package consists of a solenoid, lever and plunger assembly lever pin, and retaining ring. Make sure all Parts in the package are used. All Gasoline Engine Models The vehicle battery should be located and positioned to make use of the existing battery cables . If the battery requires relocation and longer cables are needed, larger gauge cables must be used to ensure proper voltage requirements. To ensure proper operation of the battery cables, the following chart on length, gauge and materials must be strictly adhered to. CONDITION : Starter solenoid does not engage in the ring gear during hot restart . Clicking sound is heard while trying to start the vehicle . CABLE GAUGE Reference : Chevrolet Dealer Service Technical Bulletin No. 90-332-8A (August, 1990) CAUSE : The starter solenoid engagement force is not strong enough to withstand the high temperature environment on some recreational vehicles . CORRECTION : First, check the usual causes for a "clicking" solenoid . These causes include a discharged or defective battery, defective switches, excessive 4 2 0 COMBINED LENGTH OF POSITIVE AND ' NEGATIVE CABLE IN INCHES COPPER COPPER CLAD ALUMINUM 66 107 170 52 67 111 Figure A7-12-2 - Battery Cable Gauge Specifications Figure A7-12-1- "Hot Start" Problems - Starter Solenoid 7-80 APPENDIX 7-12 "NOT START" PROBLEM CONDITIONS (Cont1d) Reference :Chevrolet Dealer Service Technical Bulletin No. 78-T-28 (April, 1978) P-Series Motor Homes with Mark IV Engines The generic term "hot start" is applied loosely to an array of causes which can lead to an inability to crank. Typical "hot start" symptoms involve failure to crank after a 20minute "hot soak" period with the engine off . Restarts are obtained by waiting for the engine compartment cool down, or in some cases, by energizing the starter solenoid directly with a screwdriver across the "S" and "B+" terminals . High ambient and/or underhood temperatures can lead to component overheating . The two starting system components, most vulnerable to adverse thermal effects, are the battery and the starter motor solenoid as follows : 1 . Batteries subjected to long-term storage or operating conditions which do not keep the battery adequately charged may be marginal because of sulfation . When operated in high ambients, electrolyte temperatures may be excessive . During engine-off hot soak periods, marginal batteries adjacent to radiators may approach the boiling point of the electrolyte, (about 230°F) depending on state of discharge . 2. The starter motor solenoid, in close proximity to the exhaust pipe, is subject to radiant heating which ultimately increases coil resistance . The resistance increase, decreases current flow to the point where the coil cannot be energized with the available applied voltage . NOTE: Some motor home body builders install batteries in a tray near the radiator, while others use a sliding shelf away from engine temperatures . The trade-off, however, is longer battery cables and a higher voltage drop . Battery thermal guards or heat shields, reflective paints, and/or battery relocation are appropriate where evidence indicates battery thermal problems. In some cases, the battery voltage available for solenoid operation is adequate when the coil is relatively cool, but insufficient when the coil is hot. Typically, the voltage drop across the ignition switch, neutral start switch circuit, to the solenoid, should not exceed 2 volts . This, normally, would allow approximately 8 volts for solenoid operation . Unfortunately, the ignition/start circuit voltage drop can exceed 4 volts due to switch contact resistance, wire lengths, etc . Since the solenoid requires a minimum of 7 volts for positive operation, a marginal or "no start" situation can occur. On "hot start" complaint vehicles that exhibit symptoms related to inoperative solenoids, the use of magnetic switch, GM Part No. 001486 or No. 1115616 (or equivalent) is recommended . It is, in effect, a high-current relay whose contacts are connected across the solenoid "S" and "B+" terminals . (See Figure A7-12-3.) The coil of the magnetic switch is connected in series with the ignition/neutral start switch circuit . Maximum available voltage is, therefore, applied to the solenoid, since the voltage drop in the magnetic switch contact circuit is virtually zero. MAGNETIC SWITCH HOLD IN WINDING SOLENOID PLUNGER SHIFT LEVER GM ' PART NO: 001486 OR GM ART NO. 1115616 i ;II1~ " II~,I 1 MITI 1110 IGNITION SWITCH CLUTCH CRANKING MOTOR BATTERY Figure A7-12-3 - Magnetic Switch/Starter Schematic 7-81 APPENDIX 7-72 "HOT START" PROBLEM CONDITIONS (Cont1d) Installation and connection of the magnetic switch can be accomplished as follows : 10. Run a functional/electric check to assure system operation . 1 . Drill two holes in the oil dipstick tube bracket . Use holes in the magnetic switch mount as a template for hole location. Removal of bracket will facilitate drilling. (See Figure A7-12-4 .) In field situations where it is impractical to install a magnetic switch, use of reflective paint to reduce heat absorption is an alternative . Remove dirt from the starter motor and solenoid . With the starter motor installed on the engine, apply reflective paint - Krylon No. 1402 High Temperature (1,200°F) Aluminum Paint, or equivalentto all accessible surface areas of the starter motor and solenoid . This is a temporary measure since any accumulation of dirt will reduce its effectiveness . 2. Mount the magnetic switch to the dipstick (tube) bracket using locking fasteners . 3. Unwrap harness tape, from engine harness wire bundle (approximately one foot) in area adjacent to magnetic switch . 4. Locate the No. 12 AWG wire with purple insulation. This wire connects the neutral start switch to the starter motor solenoid "S" terminal . 5. Cut the wire at a point which will allow connection of the severed ends to the magnetic switch. 6. Identify the cut end of the wire which connects to the "S" terminal of the starter motor solenoid. Terminate this wire with an appropriate lug for connection to one of the "large" studs on the magnetic switch. 7. Terminate the other end of the cut wire with an appropriate lug for connection to one of the "small" studs on the magnetic switch. 8. Disconnect all of the wires from the "B+" junction block and attach them to the remaining "large" stud on the magnetic switch . 9. Connect the remaining "small" stud on the magnetic switch to a secure chassis ground . WIRE TO NEUTRAL START SWITCH 12 GA.(PURPLE) WIRE ADDED AND CONNECTED TO CHASSIS GROUND 12 GA. (BLACK) Reference :Chevrolet Dealer Service Technical Bulletin No. 80-T-27 (March, 1980) G- and P-Series Models Produced Prior to March 15, 1980 - Approx. On some 1979-80 vehicles, the starter motor may not engage after the engine has been turned off and allowed to "hot soak" for a short period of time (10-15 minutes) . This condition can result from increased starter solenoid resistance when the solenoid temperature increases . Increased resistance causes reduced current flow to a point where the solenoid may not "pull-in." The symptoms are "no clicking noise" and no cranking when the ignition key is turned to the start position . If normal diagnosis of battery or wiring does not disclose any out-of-line conditions, the problem may be caused by the solenoid return spring . This problem can be corrected by installing a new shorter return spring, GM Part No. 1978281 or equivalent. Or, install a new high-heat re sistant solenoid, GM Part No., 1114458 (brown color) or equivalent, which incorporates the shorter return spring . 12 GA. (PURPLE) SEVERED ENDS OF SAME WIRE, TERMINATED AND ATTACHED TO SWITCH WIRE TO STARTER MOTOR "S" TERMINAL OIL FILLER TUBE SUPPORT 12 GA.(RED) 10 GA.(RED) 12 GA.(RED) 10 GA.(RED) THESE FOUR WIRES REMOVED FROM "B+" JUNCTION BLOCK & RECONNECTED TO SWITCH STUD AS SHOWN Figure A7-12-4 - Magnetic Switch Mounting and Connection 7-82 APPENDIX 7- 13 STARTER MOTOR ENGAGEMENT AFTER INITIAL START-UP The following information has been extracted from a Chevrolet Dealer Service Technical Bulletin concerning the starter motor relay for 7.4L engines . Problem conditions and corrective procedures are described . Reference : Chevrolet Dealer Service Technical Bulletin No. 84-41 (December, 1983) 1983-84 Motor Home Chassis The starter motor on some motor home vehicles may reengage after the engine has been started. This may result from the starter motor relay being energized after the initial start-up . Starter damage could result if this should happen. To correct the situation, replace the starter relay with a magnetic switch . (See Figure A7-13-1 .) Remove the relay connector on the existing engine harness and reterminafe the wires with the appropriate size ring terminals . This change was incorporated into production vehicles after 1984. NOTE : A square box electrical relay (GM Part No. 356284) was used in production starting October 28, 1982 with the first serial number of 302886. This relay was used until March 3, 1984. Beginning with serial number 328810, production was switched back to a magnetic switch (GM Part No. 1115616). Both switch types are mounted in the same general location. If a problem arises with electrical relay GM Part No . 356284, it should be replaced with either magnetic switch GM Part No. 1115616 or No. 001486 (interchangeable GM Part Nos.). Other 4-post, non-GM switches may be electrically and functionally similar. 12 G_ A'PURPLE ~~ 5/16-24 UNF THREAD GM PART NO. 1114537 MAGNETIC SWITCH 12 GA BLACK 8-32 UNC THREAD 18 GA BLACK 10 GA RED Figure A7-13-1- Starter Motor Relay Connections 10 GA PPL SPACER OIL FILLER UBE SUPPORT APPENDIX 7.14 GENERATOR BELT USAGE ON 6.21. DIESEL ENGINES The following information has been extracted from a Chevrolet Dealer Service Technical Bulletin concerning generator belt usage for 6 .21- engines . Reference : Chevrolet Dealer Service Technical Bulletin No. 83-103 (November, 1983) Belts installed during production were developed to withstand the characteristics of the 6.21- diesel engine. Usage of substitute belts (with the same dimensions but not construction) will not give the same performance and may wear prematurely, even while operating at the prescribed belt tension . To obtain optimum belt life, the following belts and tension settings are recommended to be used with the 6.21- diesel engine. BELT TENSION BELT USAGE RECOMMENDED BELT NEW USED Generator GM Part No . 14050449 ( .380 HiRide x 48) 175 lbs. 55-100 lbs. A/C Belt" GM Part No . 14033869 ( .380 HiRide x 60) 175 lbs. 55-100 lbs. P.S. Belt GM Part No . 14050459 ( .380 HiRide x 45'/2) 175 lbs. 55-100 lbs. 1985-Current A/C Belt GM Part No . 476406 ( .380 HiRide x 61) 175 lbs. 55-100 lbs. 1985-Current Generator GM Part No. 15592119 ( .380 HiRide x 48) 175 lbs. 55-100 lbs. Motor Home does not have factory air conditioning I NOTE : The generator/vacuum pump belt for 1984 G- and P-Series is #14071081 . This is a cog type belt, 49" x 3/8". Figure A7-14-1 - 6.2L Diesel Engine Belt Usage APPENDIX 7- 15 TORSIONAL ISOLATOR The 6.2L torsional isolator is now available from GM Parts Division. The isolator is installed in place of the present crankshaft pulley . The isolator should be installed to correct complaints of short belt life. New bolts and washers are required to install the isolator . GM PART NUMBER MODEL YEAR 15592125 P With Air Conditioning C, K, G With Air Conditioning G With Air Conditioning 1982-85 1982-84 1985 15592127 C, K, G, P Without Air_Conditioning 1982-85 1 .5592128 C, K With Air Conditioning 1985 Also Required : 4 - Bolts, GM Part No. 11500937 4 - Washers, GM Part No. 9438083 Figure A7-15 -1- Torsional Isolator Parts Identification APPENDIX 7" 16 ELECTRONIC CRUISE CONTROL The GM/AC electronic cruise control is currently available on G-Series vehicles and is proposed as an option for 1988 P-Series vehicles (under option number K34). The following information is provided as an aid to the motor home owner concerning problem conditions that may exist and corrective procedures are described . The following provides corrective actions if the electronic cruise control will not engage: 1 . Turn on the cruise control at the slide switch . Have an assistant listen near the servo positioned under the hood of the vehicle . When the ignition is turned ON, two clicks should be heard. (This means that there are 12 volts being sent through the cruise control slide switch, through the brake switch and out to the vacuum and vent solenoid valves in the servo.) 2. Remove the large hose at the servo. Applying suction by mouth, check for A complete seal. The vacuum valve should be sealed with the brake pedal released . When the brake pedal is depressed, you should lose vacuum . Replace the hose. 3. Start the engine and remove the small hose at the servo. Check to make sure there is a vacuum with the engine running . Replace the hose. 4. Turn the engine OFF and leave the ignition ON. Using a test light or a volt meter check the following positions and readings at the electronic controller box : TERMINAL A - 12 volts indicated when the slide switch is turned on. TERMINAL G - 12 volts indicated when the brake pedal is released with the slide switch on. TERMINAL M - 12 volts indicated when the resume/ accelerate switch is pushed . TERMINAL L -12 volts indicated when the set/coast button is pushed with the slide switch on . (This step checks all mode switches down to the controller.) 5 . To check the vehicle speed sensor, turn the ignition on and verify voltage to the pink wire at the yellow speed sensor connector . There should be 12 volts passing through the wire. Check to show continuity at the black wire to ground . Using a volt meter, touch TERMINAL D at the electronic controller with the engine running . Roll the vehicle slowly five or six feet in the stall . The volt meter should jump from a zero reading to between 7-1/2 and 8-1/4 volts. This indicates a good vehicle speed sensor . 6. Check the servo electrically : TERMINAL A to C should read - 30 to 55 Ohms TERMINAL E to C should read - 30 to 55 Ohms TERMINAL B to D should read - 15 to 25 Ohms 7. If any of the above checks did not provide the cause of the problem and the cruise controller still does not operate, the electronic controller box can be presumed the cause of the problem and should be replaced . CRUISE CONTROL RESPONSE A properly adjusted cable will provide a more responsive "feel" as the diaphragm has less of a chance to bottom out allowing full engine throttle. A second benefit to a properly adjusted cable is the overall smoothness of response by removing play or slack from the cable system The following is recommended to provide proper cruise control response : 1 . Adjust the cable from the cruise control 'servo to the carburetor to obtain the least amount of slack while still maintaining a normal curb idle . 2 . Lightly squeeze the rubber diaphragm on the servo control . Feel and observe cable movement as it first removes any slack and then starts throttle movement. NOTE: A proper adjustment allows only slight perceptible movement before the throttle begins . 3 . Adjustment varies by model but generally the adjustment is performed by removing the pin and moving up the adjusting holes in a stair-step series fashion . NOTE: ARA Cruise Control service parts can be obtained at S.C.S. Frigette, 1200 W. Risinet, Fort Worth, TX 76140, phone 817-293-5313. APPENDIX 7-16 ELECTRONIC CRUISE CONTROL (Cont'd) CLUTCH SWITCH (OPTIONAL) v NORMALLY OPEN CRUISE MODE CONTROL ENGAGE SWITCH BRAKE SWITCH i y ~-QIP'~.r~r .~r7 I ON OFF 4RA 3' -pr SC CONTROL MODULE CONNECTOR E I VAC VALVE IGN 1 GND SPEED SIGNAL (C3) SPEED SIGNAL (CRUISE) mar- Figure A7-16-1 - Electronic Cruise Control Schematic 1988 & Prior APPENDIX 7-16 ELECTRONIC CRUISE CONTROL (Cont'd) 1989-94 ELECTRO-MOTOR CRUISE SYSTEM DESCRIPTION The Electro-Motor Cruise Control is a speed control system which maintains a desired vehicle speed under normal driving conditions. The Electro-Motor Cruise Control System has the capability to cruise, coast, resume speed, accelerate, tap-up, and tap-down. The main parts of the cruise control system are the mode control switches, cruise control module, electrical release switches, and electrical harness . The cruise control system uses a control module to obtain the desired vehicle cruise operation (figure 1). Two important components in the module help to do this. One is an electronic controller and the second is an electric motor. The controller monitors vehicle speed and operates the electric motor. The motor moves a connecting strap and throttle linkage in response to the controller motor to maintain the desired cruise speed . The cruise control module contains a low speed limit which will prevent system engagement below about 25 mph . The operation of the controller is controlled by mode control switches located on the turn signal lever. separately mounted plunger type release switch. This is a redundant switch. When the brake pedal is depressed, each switch disengages the cruise control system . The cruise function remains disengaged after the brake pedal is released . CRUISE CONTROL MODULE The cruise control module is mounted on the top of the radiator support on the driver side. The cruise control module has an electronic controller and an electric motor to vary the throttle with each different cruise control mode. The cruise control module is not serviceable in the field. DO NOT ATTEMPT TO REPAIR THE MODULE . NOTE; The factory installed cruise control servo cable can be ordered separate . #25075767 MODEL CONTROL SWITCH The mode control switch controls the various operating modes of the cruise control system . The switch is located on the multi-function lever. VEHICLE SPEED SENSOR 1989 The P. Motorhome Cruise Control system uses only the input provided by the vehicle speed sensor located in the back of the speedometer head to maintain desired speeds. This system does not use vacuum or a servo . NOTE : Effective SOP 1994 The previous K34 cruise control option will now be standard equipment from the factory. ELECTRIC BRAKE RELEASE SWITCH The brake pedal has two switches when a vehicle is equipped with cruise control . The combination stop light/cruise control switch is used in series with a Figure A7-16-2 - Cruise Control Module NOTE: Starting in 1991 with the overdrive transmission, the switch mounted near the top of the brake pedal bracket controls the Torque Con vertor Clutch (TCC) in the 4L80EHD Transmission . Additional information see bulletin #90-368-8C Page4 or Bulletin 91-137-9 Page 1 APPENDIX 7-16 ELECTRONIC CRUISE CONTROL (Cont'd) CHART A IGNITION OFF DISCONNECT CONNECTOR C4A FROM CRUISE MODULE . IGNITION "ON" MEASURE VOLTAGE AT TERMINAL F OF C4A TO A GOOD GROUND . IGNITION "OFF" WITH OHMMETER MEASURE RESISTANCE OF BLK/WHT WIRE (450) FROM TERMINAL E OF C4A TO ENGINE BLOCK GROUND STUD . CHECK GAGES FUSE AND SPEEDO FUSE . CHECK PNK WIRES (39A, 39B) AND PINK/BLK WIRES (39A, 39C) FOR OPEN . LESS THAN 1 OHM GREATER THAN 1 OHM MEASURE VOLTAGE AT TERMINALS A, B, C, D OF C4A TO GROUND WITH CRUISE LEVER SWITCH OFF AND IGNITION ON . CHECK ENGINE BLOCK GROUND STUD FOR A CLEAN AND TIGHT CONNECTION . CHECK CONDITION OF BLK/WHT WIRE (450) FROM TERMINAL E OF C4A TO ENGINE BLOCK GROUND STUD . 0 VOLTS AT ALL TERMINALS 12 VOLTS AT ONE OR MORE TERMINALS MEASURE VOLTAGE AT TERMINALS B AND C OF C4A TO GROUND WITH CRUISE AND IGNITION SWITCHES ON . " DISCONNECT CONNECTOR C3A. MEASURE VOLTAGE AGAIN AT TERMINALS A, B, C, AND D OF CONNECTOR C4A. " IF ALL TERMINALS READ ZERO VOLTS, REPLACE CRUISE CONTROL LEVER. " IF ONE OR MORE TERMINALS READ 12 VOLTS, PROBLEM IS IN WIRING HARNESS. REPLACE CRUISE CONTROL LEVER Figure A7-16-3 - Diagnosis of the Cruise Control System - Chart A 7-89 APPENDIX 7-16 ELECTRONIC CRUISE CONTROL (Cont1d) CHART B FROM CHART A , MEASURE VOLTAGE AT TERMINALS A AND D OF C4A TO GROUND WITH, CRUISE LEVER SWITCH AND IGNITION SWITCH ON . 0 VOLTS AT A AND D 0 VOLTS ONLY AT D 0 VOLTS ONLY AT A " CHECK FOR 12 VOLTS AT TERMINAL A OF FEMALE HALF OF CONNECTOR C3A. IF ZERO VOLTS, CHECK FOR OPEN IN PNK WIRE (39C). " CHECK CONTINUITY BETWEEN TERMINALS A AND B OF MALE HALF OF C3A WITH CRUISE SWITCH ON . IF OPEN, REPLACE CRUISE CONTROL LEVER. " CHECK FOR OPEN IN GRA WIRE j397B) . " CHECK FOR OPEN OR MISADJUSTED BRAKE SWITCHES . " CHECK FOR OPEN IN BRAKE/CLUTCH SWITCH WIRING FROM SPLICE S2AA TO TERMINAL D OF C4A . CHECK FOR AN OPEN IN GRA WIRE (397A) . 12 VOLTS AT A AND D CRUISE SWITCH ON AND "SET" PUSH f B U TTON DEPRESSED. MEASURE VOLTAGE AT TERMINAL B OF C4A TO GROUND . 12 VOLTS 0 VOLTS MEASURE VOLTAGE AT TERMINAL C OF C4ATO GROUND WITH CRUISE SWITCH IN R/A POSITION . 0 VOLTS " PUT VOLTMETER ON DC VOLTAGE SCALE. " CONNECT VOLTMETER ACROSS PINS F AND K OF CONNECTOR C4A. " IGNITION ON, RAISE VEHICLE, PUT TRANSMISSION IN NEUTRAL. " SPIN DRIVE WHEELS BY HAND . " DISCONNECT CONNECTOR C3A AND CHECK CONTINUITY BETWEEN TERMINALS B AND D OF MALE HALF WITH "SET" PUSH BUTTON DEPRESSED. IF OPEN, REPLACE CRUISE CONTROL LEVER . " CHECK FOR OPEN IN DK BLU WIRE (84) . " DISCONNECT C3A AND CHECK CONTINUTIY BETWEEN TERMINALS A AND, C OF MALE HALF WITH WITH CRUISE SWITCH IN R/A POSITION . IF OPEN, REPLACE CRUISE CONTROL LEVER. " CHECK FOR OPEN IN DK GRN WIRE (83) . Figure A7-16-4 - Diagnosis of the Cruise Control System - Chart B 7-90 APPENDIX 7-16 ELECTRONIC CRUISE CONTROL (Cont'd) CHART C FROM CHART B VOLTAGE VARYING BETWEEN ZERO AND 12 VOLTS . RECONNECT CRUISE MODULE CONNECTOR C4A . 0' VOLTS y-CHECK FOR OPEN ON BRN/WHT WIRE (437 AND 437A) . " START ENGINE " MOVE CRUISE SWITCH TO ''OFF" " MOVE CRUISE SWITCH TO "ON' AND THEN WAIT AT LEAST 3 SECONDS BEFORE DOING NEXT STEP. " FULLY DEPRESS AND HOLD BRAKE PEDAL . " PUSH CRUISE "SET" PUSH BUTTON IN AND HOLD . " HOLD CRUISE SLIDER SWITCH IN "R/ A" POSITION . " AFTER 10 SECONDS, RELEASE BRAKE PEDAL AND LISTEN FOR MOMENTARY ENGINE RPM INCREASE . ENGINE RPM INCREASE . " PROBLEM IS INTERMITTENT . " CHECK CONNECTORS AND WIRE TERMINALS FOR CONTAMINANTS (OIL, GREASE, DIRT) AND FOR PROPER CONTACT . " ALSO CHECK GROUND TERMINALS FOR CONTAMINANTS AND CONTACT . 12 VOLTS [ _ CHECK FOR SHORT TO GROUND ON BRN/WHT WIRES (437, 437A) NO OPENS OR SHORTS IN WIRE . REPLACE VEHICLE SPEED SENSOR . NO ENGINE RPM INCREASE . " CHECK THAT CRUISE MODULE LINKAGE IS CONNECTED AND OPERATING FREELY . " CHECK LINKAGE ADJUSTMENT . " CHECK TERMINALS IN CONNECTORS C3A, C4A, C5A FOR CONTAMINANTS (OIL, GREASE, DIRT) AND FOR PROPER CONTACT . IF OK, REPLACE CRUISE CONTROL MODULE . Figure A7-16-5 - Diagnosis of the Cruise Control System - Chart C Additional information and diagnostics can be found in the C-K Pickup Shop Manual for the EMCS cruise control . SECTION 7F - ENGINE EMISSION CONTROLS ENGINE EMISSION CONTROLS VEHICLE EMISSION CONTROL INFORMATION LABEL The Vehicle Emission Control Information Label (Figure 7-56) is located in the engine compartment (fan shroud, radiator support, hood underside, air cleaner, etc .) of every vehicle produced by General Motors Corporation . The label contains important emission specifications and setting procedures, as well as a vacuum hose schematic with emission components identified. When servicing the engine or emission system, the Vehicle Emission Control Information Label should be checked for up-to-date information . bF = FILTERED AIR 00 B = BLOW-BY GASES 7*F+B COMBUSTIBLE MIXTURE EMISSION CONTROLS -SYSTEMS AND COMPONENTS GENERAL DESCRIPTION POSITIVE CRANKCASE VENTILATION (PCV) SYSTEM - GASOLINE ENGINE Because small amounts of combustion gases seep past the piston rings, all engines have a closed Positive Crankcase Ventilation System to provide more complete scavenging of crankcase vapors (Figure 7-57) . Figure 7-57 - PCV System - Gasoline Engine -Typical LABEL CODE ENGINE SIZE EXHAUST EMISSION FAMILY EVAPORATIVE EMISSION FAMILY ADJUSTMENT PROCEDURE ZFT "NGYO7MWN7 I IMPORTANT ENGINE IN ..MATRON GENERAL MOTORS " ' .NBATION SET PARKING BRAKE AND BLOCK DRIVE WHEELS. MAKE ADJUSTMENTS WITH ENGINE AT NORMAL OPERATING TEMPERATURE, CHOKE FULL OPEN, AIR CLEANER INSTALLED AND AIR CONDITIONING OFF . PUT TRANSMISSION IN PARK OR NEUTRAL FOR ALL SETTINGS . 1. 2. S. DISTRIBUTOR: DISCONNECT AND PLUG VACUUM HOSE AT DISTRIBUTOR . SET IGNITION TIMING AT SPECIFIED ENGINE SPEED . UNPLUG AND RECONNECT VACUUM HOSE TO DISTRIBUTOR. IDLE SPEEDSCREW : ADJUST IDLE SPEED SCREW TO SPECIFIED SPEED. FAST IDLE SPEED SCREW: DISCONNECT AND PLUG VACUUM HOSE AT EGR VALVE, CANISTER PURGE HOSE AND CANISTER PURGE SIGNAL HOSE AT CANISTER . ADJUST FAST IDLE SPEED SCREW TO SPECIFIED SPEED WITH LIVER ON HIGH STEP OF CAM. UNPLUG AND RECONNECT HOSES TO EGR VALVE AND CANISTER . FUEL REQUIREMENTS - USE 89 OCTANE OR HIGHER . CRANKCASE BLOW-BY GASES ENGINE ADJUSTMENT SPECIFICATIONS A.I.R./E.G.R. TIMING ( "BTC ® RPM) IDLE SPEED SCREW (RPM) AUTOMATIC A " ® 700 700 FAST IDLE SPEED SCREW (RPM) 1900 SPARK PLUG GAP (IN .) VALVE LASH O.0A5 HYD . IDLE MIXTURE SCREWS ARE PRESET AND T FACTORY. PROVISION FOR ADJUSTMENT WRING TUNE-UP IS HQj PROVIDED. SEF SERVICE MANUAL. MAINTENANCE-SCHFDULE AND EMISSION HOSE ROUTING DIAGRAM FOR ADDITIONAL INFORMATION . THIS ENGINE CONFOINS TO U.S. EPA REGULATIONS APPLICABLE TO 1987 MODEL YEAR NEW HEAW DUTY ENGINES . THIS [ONE IS CERTIFIED FOR USE IN ALL HEAVY-DUTY VEHICLES. EMISSION COMPONENT AND VACUUM HOSE SCHEMATIC Figure 7-56 - Vehicle Emission Control Information Label 7-92 SECTION 7F ENGINE EMISSION CONTROLS Ventilation air is drawn through a separate filter from the "dirty air" side of the air cleaner, through a hose down into the crankcase, up through the ventilator valve, through another hose and into the intake manifold . The intake manifold vacuum draws any fumes from the crankcase to be burned in the engine . Periodically check for oil deposits in the air cleaner . The system has been designed as a closed system. If there are oil deposits on the air cleaner element or a puddle of oil found at the bottom of the air cleaner base, check the entire system for oil leaks . A leak in the system will allow reverse air flow from pulldown with the carburetor air flow drawing oil fumes out of the right-hand rocker cover into the air cleaner . Potential leak points include an incorrect oil fill cap, a leak at the dipstick or rocker cover. (See Figure 7-58.) Fresh air enters the engine through the combination filter, check valve and oil fill cap. The fresh air mixes with blowby gases and enters the right cover. The gases pass through a filter on the valve cover and are drawn into the connecting tubing . The intake manifold vacuum acts against a spring-loaded diaphragm to control the flow of crankcase gases. Higher intake vacuum levels pull the diaphragm closer to the top of the outlet tube. This reduces the amount of gases being drawn from the crankcase and decreases the vacuum level in the crankcase. As the intake vacuum decreases, the spring pushes the diaphragm away from the top of the outlet tube, allowing more gases to flow to the intake manifold . EARLY FUEL EVAPORATION (EFE) SYSTEM - GASOLINE ENGINE The EFE system is used to provide a source of rapid heat to the engine induction system during cold driveaway. Rapid heating is desirable because it provides for quick fuel evaporation and more uniform fuel distribution to aid cold drivability . It also reduces the length of time carburetor choking is required, making reductions in exhaust emission levels possible. EFE systems may use a valve which increases the exhaust gas flow under the intake manifold during cold engine operation . The valve is vacuum-operated and is controlled by a thermal vacuum switch (TVS) which applies vacuum when the coolant temperature is below the calibration valve. THERMOSTATIC AIR CLEANER (THERMAC) -GASOLINE ENGINE Figure 7-58 - Dipstick and Tube Assembly Potential Leak Points CRANKCASE VENTILATION DIESEL ENGINE A Crankcase Depression Regulator Valve is used to regulate (meter) the flow of crankcase gases back into the engine . The Crankcase Depression Regulator Valve (CDRV) is designed to limit vacuum in the crankcase as the gases are drawn from the valve cover through the CDRV and into the intake manifold (air crossover) . The Thermostatic Air Cleaner (THERMAC), shown in Figure 7-59, uses a damper door in the air cleaner inlet, controlled by a vacuum diaphragm motor to mix preheated and nonpreheated air entering the air cleaner to maintain a controlled air temperature into the carburetor. The vacuum motor is modulated by a temperature sensor in the air cleaner. The preheating of the air cleaner inlet air allows leaner carburetor and choke calibrations resulting in lower emission levels, while maintaining good drivability . The preheated air is obtained by drawing inlet air through a stove attached to the exhaust manifold . On vehicles which have been converted to burn LPG- or CNG-type fuel, by the motor home body manufacturer, the GM air cleaner and Thermac system may have been removed . This can result in a cold engine stumble especially atcold temperatures, when operating on gasoline as opposed to LPG- or CNG-type fuels . SECTION 7F - ENGINE EMISSION CONTROLS THERMAC AIR CLEANER ASSEMBLY VACUUM HOSE TO INTAKE MANIFOLD TEE Figure 7-59 - Thermac Air Cleaner - Typical EVAPORATIVE EMISSION CONTROL SYSTEM (EELS) GENERAL DESCRIPTION zzc V®IKAE EVAPORATIVE MSSNNI COMM INFORMATION GENERAL MOTORS EORPORATION EVAPORATIVE EMISSION FAMILY MAXIMUM CERTIFIED FUEL TANK CAPACITY FOR EVAPORATIVE SYSTEM NoM080.00EAl 00 GALLONS (NOMINAL) TWO CANISTERS PLUS AIR CLEANER VAPOR STORAGE =O11S CORMTDO N" OETIENIED THAT THIS V61NE CarGRAS TGG. . 1P. 114119-T=5 Y1lKYlE TO 1W 11006 YEARUK NEW OA50M-ERR HEAVY-OIITT VENC16 WIBI LOAVES®VNTN A 110NEEM RR TASK CAPACITY To UM 60 GAl1ONS. ASOIN WIS1101 TO ADD RAN, TAR WACITT YTOID THE AMVA MA%OEW MUST RESENT A 1110TIN1 STATB101T 10 THE VA ARIIR1UTOR THAT THE NSOMCAROO STORAGE STAR 11At 1N1 UPGRADED ACCORID To TIN RaADrNns Io Cn 11187-190 *FT. 110. 100"50 a Figure 7-60 - Vehicle Evaporative Emission Control Information Label The Vehicle Evaporative Emission Control Information label (Figure 7-60) contains the government regulations for the evaporative emission control system, vapor storage requirements and fuel tank capacity for the evaporative system . The Evaporative Emission Control System (EECS) shown in Figure 7-61 limits the amount of fuel vapor into the atmosphere. The system traps fuel vapor from the fuel tank and carburetor float bowl into a fuel vapor canister . The fuel tank has a non-vented fuel cap and a single vent pipe to the canister. The canister absorbs and stores the fuel vapor in a carbon element until it can be removed and burned during the normal combustion process . When the engine is running, a thermostatic vacuum switch determines when the fuel vapor is purged into the intake air flow. SECTION 7F - ENGINE EMISSION CONTROLS TO TCC ON A/T, TO EGR ON M/T CANISTER PURGE CONTROL VALVE ACTIVATED CARBON ELEMENT CARBURETOR ASSEMBLY VALVE ASM. BOWL VENT VAPOR RESTRICTION I Figure 7-61- Evaporative Emission Control System (EECS) The Evaporative Emission Control System uses the following control valves : e Purge control valve mounted on the canister . e Vapor vent valve mounted on the canister. e A thermal bowl vent valve (some applications) . The thermal bowl vent valve (TBVV) is located in the section of hose that connects the carburetor bowl vent fitting to the canister control valve. The TBVV will close and prevent vapor movement at 32°C (90°F) and below. The TBVV will open at 49°C (120°F) to permit vapor flow to the canister control valve . e A thermostatic vacuum switch (TVS) installed in the intake manifold to sense engine coolant temperature . FUEL VAPOR CANISTER - PRIMARY When the engine is shut off, manifold vacuum is lost at the vapor vent valve . The spring-loaded valve in the vapor vent valve now connects the carburetor bowl vent to the canister. Carburetor float chamber vapors now pass into the canister for storage . When the engine is restarted, manifold vacuum draws the vapor vent controlling valve against spring pressure, closing off the bowl vent . Ported vacuum from the carburetor is connected to the TVS . When the TVS opens, ported vacuum opens the purge control valve . When the valve opens, manifold vacuum draws vapors from the canister into the intake manifold. Gasoline vapors from the fuel tank flow into the tube labeled "FUEL TANK," and vapors from the carburetor float bowl flow into the tube labeled "CARB BOWL," and are absorbed by the carbon. The canister is purged when the engine is running above idle speed . The closed bottom design keeps water from entering the bottom of the canister, freezing, and restricting purge air flow. During purge, air is drawn from the clean side of the air cleaner, to the The basic large-size, two-chamber, closed bottom primary fuel vapor canister is shown in Figure 7-62. This canister is used on all systems . SECTION 7F ENGINE EM ISSION CONTROLS v D D skk inuuinuwuw v. wmnnun _ .W y.l .y.. 10 v !R01R 51 ~~ niuu III _ V `` V ttuun vuuuuta viuum. "aonnm wm r 0 LARGE SIZE TWO CHAMBER CLOSED' BOTTOM CANISTER VAPOR VENT CONTROL VALVE PURGE CONTROL VALVE CLEAN AIR TUBE "AIR CLNR" VAPOR FROM FUEL TANK VAPOR FROM BOWL VENT TO MANIFOLD VACUUM SIGNAL TO PORTED VACUUM VAPOR TO PURGE LINE FILTER CARBON BOTTOM COVER DUST CAP AIR FLOW Figure 7-62 - Fuel Vapor Canister -- Primary tube on the canister labeled "AIR CLNR," through the carbon and into the intake manifold to be burned. Some closed bottom canisters draw purge air directly from the atmosphere . Canister Purge Control Valve The canister purge control valve shown in Figure 7-62 is a spring-biased diaphragm valve, normally closed, which allows or prevents purging of the canister . When the engine is off or idling, the spring holds the valve closed preventing canister purge. When the engine is off idle, however, timed manifold vacuum pulls the diaphragm upward and opens the valve allowing the canister to be purged . FUEL VAPOR CANISTER - AUXILIARY An Auxiliary Fuel Vapor Canister shown in Figure 7-63 is added to a primary closed bottom canister to increase capacity when a dual (auxiliary) fuel tank is used. On the bottom is a hose which connects to the primary canister's purge air inlet . On top is a purge air inlet. Vapor overflowing from the primary canister is stored in the auxiliary canister. During purge, vapor flows through the auxiliary canister, the primary canister and into the intake manifold for burning during combustion. AUXILIARY CANISTER ] *.1404000, Vapor Vent Control Valve The vapor vent control valve shown in Figure 7-62 prevents venting of the carburetor float bowl during engine operation . A spring-biased diaphragm valve, normally open, allows (or prevents) fuel vapors from the float bowl to enter the canister. When the engine is off, spring tension holds the valve open, allowing normal venting . When the engine is turned on, however, manifold vacuum pulls the diaphragm up to the valve . DUST CAP AIR FLOW DURING PURGE FILTERS CARBON *,VAPORS FROM PRIMARY CANISTER Figure 7-63 - Fuel Vapor Canister - Auxiliary 7-96 SECTION 7F ENGINE EMISSION CONTROLS MAINTENANCE AND INSPECTION POSITIVE CRANKCASE VENTILATION (PCV) - GASOLINE ENGINE An engine which is operated without any crankcase ventilation can be damaged seriously . Therefore, it is important to replace the PCV valve (GM Part No. 6487779 ; AC CV774C or equivalent - 5.71- and Mark IV engines) at the recommended intervals. If an engine is idling too slowly or roughly, this may be caused by a clogged ventilator valve or plugged hose; therefore, never adjust the carburetor idle without first checking the PCV valve and hose. With this system any blow by in excess of the system capacity (from a badly worn engine, sustained heavy load; etc.) is exhausted into the air cleaner and is drawn into the engine. Proper operation of the PCV System is dependent on a sealed engine. If oil sludging or dilution is noted, and the PCV System is functioning properly, check engine for possible cause and correct to ensure that the system will function as intended. Checking the PCV System 1 . Remove PCV valve from intake manifold or rocker arm shaft cover. 2. Run the engine at idle. Figure 7-64 - PCV Valve Checking EFE System 1 . With the engine cold, position the transmission in neutral or park and apply parking brake. 2. Start the engine and observe movement of the actuator rod and exhaust heat valve. Valve should move to its closed position. 3. If the valve does not close, disconnect the hose at the actuator and check for vacuum . " If there is vacuum, replace the actuator . 3. Place your thumb over end of valve to check for vacuum . If there is no vacuum at valve, check for plugged hoses or valve . Replace plugged and/or deteriorated hoses. " If . there is no vacuum, disconnect the hose at the TVS to vacuum source . " If there is vacuum at the hose, replace the TVS. 4. Shut off engine and remove PCV valve . Shake valve and listen for the rattle of check needle inside the valve. If valve does not rattle, replace valve (Figure 7-64). Remove PCV valve from rubber hose and look up the end of the hose using a flashlight. If the hose appears coated "oil wet," replace the PCV valve . 4. When the coolant reaches 180°F, the exhaust heat valve should move to its open position . 5. After installing a new PCV valve, readjust engine idle if necessary . 5. If the valve does not move, disconnect the hose at the actuator and check for vacuum . " If there is no vacuum, check for deteriorated hose and vacuum source to determine the lack of vacuum . " If there is vacuum, replace the TVS . EARLY FUEL EVAPORATION (EFE) Inspection " If there is no vacuum, replace the actuator . " Visually inspect the exhaust heat valve (Figure 7-65) for damage or binding linkage. " Check that the linkage is connected and the vacuum hoses are properly routed and connected. " Move exhaust heat valve by hand. If binding or stuck, free it with manifold heat valve lubricant, GM Part No. 10504022 or equivalent . If the valve cannot be freed, replace the valve . AIR INJECTION REACTOR (A.I .R.) SYSTEM - GASOLINE ENGINE The Air Injection Reactor (A.I.R.) System (Figure 7-66) consists of: an air injection pump (with necessary brackets and drive attachments), an air diverter valve, a check valve, and an air pipe assembly for each exhaust manifold, and connection hoses . 7-97 SECTION 7F - ENGINE EMISSION CONTROLS Figure 7-65 - Exhaust Heat Valve - EFE System Inspection Accelerate the engine to approximately 1,500 RPM and observe air flow from the hose(s) . If the air flow increases as the engine is accelerated, the pump is operating satisfactorily . If the air flow does not increase or is not present, proceed as follows : 1 . Check for proper drive belt tension . The A.I.R. system is not completely noiseless . Under normal conditions, noise rises in pitch as engine speed increases . To determine if excessive noise is the fault of the system, operate the engine with the pump drive belt removed . If excessive noise does not exist with the belt removed, proceed as follows : 2. Check for a seized air injection pump. Do not oil the pump. 3. Check hoses, . pipes and all connections for leaks and proper routing . NORMAL FLOW SHOWN BY BLACK ARROWS: BYPASS CONDITIONS SHOWN BY CROSSHATCHED ARROWS. TUBE ASSEMBLY HIGH SPEED BYPASS AIR PUMP ." IIUv . ,.W DECELERATION BYPASS EXHAUST PORT DIVERTER VALVE Figure 7-66 - Air System - Typical 7-98 MANIFOLD VACUUM SOURCE SECTION 7F - ENGINE EMISSION CONTROLS 4. Check diverter valve attaching screws for tightness . 5 . Check injection pump for proper mounting and bolt torque . 5. Start the engine . Watch the damper door in the air cleaner snorkel . When the engine. is first started, the damper door should close . As the air cleaner warms up, the damper door should open slowly. as 6. If the damper door does not close when the engine is started, remove the air cleaner . 7. If no irregularities exist and the air injection pump noise is still excessive, remove and replace the pump. 7. Apply at least 7 in. of vacuum to the vacuum diaphragm motor through the hose disconnected at the temperature sensor. The damper door should completely block off the snorkel passage when vacuum is applied . If not, check to see if the linkage is hooked up correctly . 6 . Repair irregularities in these components necessary. Air Pump Drive Belt Adjustment and Replacement 1 . Inspect drive belt for wear, cracks and deterioration . 2. Loosen the alternator adjustment bolt. 3. Replace the belt if required . 4. Move the alternator or pump until the drive belt is at the proper tension, then retighten bolts . See Appendix A- Drive Belts and Tension Specifications at the back of this manual for specifications . 5. Check the belt tension using a belt tension gage. CHECK VALVE INSPECTION 1 . The check valve should be inspected whenever the hose is disconnected from the check valve or whenever check valve failure is suspected. (A pump that had become inoperative and had shown indications of containing exhaust gases in the pump would indicate check valve failure .) 2. Blow through the check valve (toward the cylinder head) then attempt to suck back through check valve. Flow should only be in one direction (toward the exhaust manifold) . Replace valve which does not function in this manner. THERMOSTATIC AIR CLEANER Checking Thermac Air Cleaner 1 . Inspect the system to be sure all hoses and tubes are connected . Check for kinked, plugged or deteriorated hoses . 2. If the engine is warm or above 80°F, remove the air cleaner, Allow it to cool to room temperature, below 80°F. Place a cool wet rag on the temperature sensor to aid in cooling . 8. With the vacuum still applied, trap vacuum in the vacuum diaphragm motor by bending the hose. The damper door should remain closed ; if not, replace the vacuum diaphragm motor assembly. (Failure of the vacuum diaphragm motor assembly is more likely to be caused by binding linkage or a corroded snorkel than by a failed diaphragm . This should be checked first, before replacing the diaphragm .) 9 . Reinstall the air cleaner. As the engine warms up, the damper door should start to allow outside air and heated air to enter the carburetor. 10 . If the air cleaner fails to operate as described above or if the correct operation of the air cleaner is still in doubt, perform a thermometer check of sensor. Thermometer Check of Sensor 1 . Start the test with the air cleaner temperature below 80°F . If the engine has been run recently, remove the air cleaner and place the thermometer as close as possible to the sensor . Let the air cleaner cool until the thermometer reads below 79°F, about 5 to 10 minutes. Reinstall the air cleaner on the engine and continue to Step 2 below . 2. Start and idle engine. The damper door should move to close the snorkel passage immediately if the engine is cool enough . When the damper door starts to open the snorkel passage (in a few minutes), remove the air cleaner cover and read the thermometer . It must read between 100°F and 130°F. 3. If the damper door does not start to open up the snorkel passage at the temperature indicated, the temperature sensor is malfunctioning and must be replaced. Air Cleaner Element and PCV Filter Replacement 3. Install the cooled air cleaner with cold air intake dis- PAPER ELEMENT connected from snorkel (if equipped) . 1 . Remove the air cleaner cover. 4. Observe the damper door before starting the engine . It should be in the open snorkel position (hot air duct covered .) 7- 99 2. Remove the air cleaner element and PCV filter. 3. Install anew element and PCV filter in the air cleaner . SECTION 7F - ENGINE EMISSION CONTROLS 4. Reinstall the air cleaner cover. Do not overtighten wing nut . POLYWRAP ELEMENT (P-SERIES) 1 . Remove the air cleaner cover . 2. Remove the element. NOTE: Never use a hot degreaser or any solvent containing acetone or similar solvent ; also, never shake, swing or wring the element to remove excess solvent as this may tear the polyurethane material . Instead, "squeeze" the excess solvent from the element. Squeezing will avoid damaging the element material. 3. Remove the polywrap band from the paper element and discard the element (Figure 7-67) . 7. Dip the band into light engine oil and squeeze out the excess oil . 4. Clean the bottom section of the air cleaner and inspect the cover seal for tears or cracks . Replace the seal if damaged . 8. Install the band around the outer surface of the new paper element. 9. Install the element in the bottom section of the air cleaner with either end up. 5. Inspect the band for tears and replace if damaged . 6. If the band is serviceable, wash it in kerosene or mineral spirits and squeeze out the excess solvent . 10. Install the air cleaner cover. Do not over-torque the wing nut(s) . NOTE : Some models and years do not use the Polywrap Air Cleaner System . Some models and years are equipped with a molded charcoal evaporative filter that is permanently attached to the air cleaner base. DO NOT ATTEMPT TO REMOVE OR SERVICE THIS FILTER. The function of this filter is to collect fuel vapors on engine shutdown. This filter "self-purges" as the engine is running . (See Figure 7-61). NOTE: POLYURETHANE BAND MUST WRAP OVER BOTH END SEALS OF PAPER ELEMENT AS SHOWN POLYWRAP AIR CLEANER ELEMENT (BAND SHOWN) MOLDED CHARCOAL EVAPORATIVE FILTER n PAPER FILTER PORTION OF POLYWRAP AIR CLEANER ELEMENT NOTE: POLYURETHANE BAND MUST COMPLETELY COVER THE OUTER SCREEN SURFACE OF PAPER ELEMENT AS SHOWN . WING NUT TORQUE AT 20 IN. LBS. AIR CLEANER ELEMENT (PAPER FILTER PORTION) POLYWRAP AIR CLEANER ELEMENT (BAND SHOWN) NOTE: 1993-94 uses double stud and wing nut . Figure 7-67- Polywrap Air Cleaner 7- 100 APPENDIX 7-17 H,51) EMISSION SYSTEM On vehicles equipped with the H5D emission system (vehicles rated over 8,600 GVW and built after January 1, 1985), the "CHECK ENGINE" light may light up to inform the motor home owner of a possible problem while a problem does not actually exist. The following diagnostic procedure should be followed in correcting this condition . NOTE : The "CHECK ENGINE" light will normally come on when the ignition is turned to the "ON" position and the engine is NOT running . This is provided as a bulb check . AIR DIVERT SOLENOID 1 . Check the A.L.R. solenoid and A.I .R. moduled connectors for a proper connection . 2. With ignition on, disconnect each solenoid connector and with a test light, check for a light across the terminals . (See Figure A7-17-2.) TO AIR CLEANER OR SILENCER O~ CHECK VALVE SOLENOID CONNECTOR The illumination of the "CHECK ENGINE" light indicates that there is a malfunction in the A.I.R. solenoid control module or wiring . (See Figure A7-17-1 .) Perform the following corrective procedure : SOLENOID CONNECTOR TO EXHAUST PORTS B IGNITION 1 D 93 AIR DIVERT TO AIR SOLENOID CLEANER I'r1 SOLENOID CONNECTOR A CONTROL MODULE CHECK VALVE TO EXHAUST PORTS Figure A7-17-1- A.I.R. Connector Diagram "CHECK ENGINE" LIGHT APPENDIX 7-17 H51) EMISSION SYSTEM (Cont'd) BRACKET (FLOOR PANEL) TYPICAL MOUNTING LOCATION FOR ELECTRIC FUEL PUMP RELAY IF EQUIPPED - GM PART NO. 15528707. (See Figure A7-7-4 and Figure A7-7-5 .) NOTE : TYPICAL FACTORY LOCATION FOR MOTOR HOME AND COMMERCIAL "P" MODEL. A.I .R. CONVERTER MODULE ASSEMBLY RADIATOR ASSEMBLY Figure A7-17-2 - A .I.R. Connector Module and Electric Fuel Pump Relay Locations 1989 & Prior 3. If O.K. (light on), check solenoid coil resistance and if less than 20 ohms, replace the solenoid and valve. 5. If not O.K . (light off), check for an open circuit to the module. 4. If not O.K. (light off), connect the solenoid connector(s) and disconnect connector at module . With a test light, check for a light between terminal "A" and "B." 6. If O.K. (light on), replace the module . (See parts listing in Figure A7-17-4 .) APPENDIX 7-17 H51) EMISSION SYSTEM (Cont'd) OVERRIDE RELAY (454 ONLY) A.I.R . DIVERT MODULE - NOTE : A.I.R. DIVERT MODULE FOR "C" TRUCKS IS MOUNTED ON THE FIREWALL ENGINE HARNESS FRONT Figure A7-17-3 - H5D Override Relay NOTE: 1985-1990 models equipped with the LE8 (454) and H5D have an override relay . (See Figure A7-17-3) . This relay is necessary dur to the lower cranking speed of the LE8 (454) engine . If the relay fails, the CEL will come on. If it becomes necessary to replace the relay or the module, use the part numbers listed in Figure A7-17-4 . GM PART NO. DESCRIPTION & APPLICATIONS QUALITY 100669221 Module 1985-89 W/LE8 454 1 14087500 Module 1985 W/LT9 350 1 14102010 Module 1986 W/LT9 350 1 14100876 Module 1985-Current W/L25 292 1 15528707 Relay 1985-89 W/LE8 454 1 14103304 Relay 1990-1993 N/L19 454 1 10052973 Module 1990-1993 N/L19 454 1 10052954 Module 1994 N/L19 454 1 Figure A7-17-4 - 454 and H5D Override Relay Parts List 7-103 APPENDIX 7.17 H51) EMISSION SYSTEM (Cont'd) a~u~a 10052954 (4815A) 11501907 (4815K) 0 19 MOOUIE ASM STRAP The 1990 fuel module Part #10052973 is connected to the instrument panel wiring harness . The module and instrument panel wiring harness are shipped loose and must be installed by the body builder. This fuel cycler override module is necessary due to the lower cranking speed of the L19 (454) engine . The module overrides the ECM for 20 seconds to provide fuel pressure to the injector. APPENDIX 7-17 H51) EMISSION SYSTEM (Cont1d) Figure A7-17-5 - A.I.R. Pump Failure - 1985 112 thru 1989 454 H5D Emissions Due to the relocation of the A.I.R. Pump Filter Canister to the right front wheel well by the body builder, the canister must be sealed or shielded to prevent water, salt and dirt thrown by the tire to enter the A.I.R System through the hose connections at the bottom of the canister and/ or through the lid at the top of the canister . See Figure A7-17-5. The air inlet hose must also be located away from direct water spray and sealed where it is attached to the core support . Sealing the canister can be accomplished by applying a bead of Permatex No . 2 Sealer, or equivalent, to the canister hoses and lid . 1 . Loosen inlet and outlet hose clamps and remove hoses from A.I .R. Filter Canister . Clean hose connections . 2. Remove and clean canister lid . 3. Apply a bead of Permatex No. 2 Sealer, or equivalent, to the canister inlet and outlet hose connections and inside circumfrence of the canister lid. Reinstall lid and hoses. 4. Tighten hose clamps securely. NOTE : Production mounting of the A.I.R. Filter Canister is in the vertical position (canister lid facing up) . An alternative method of eliminating water con tamination would be to remount the canister horizontally (lid facing the right side of the vehicle), and rotate the canister in the clamp so that the two air outlets are positioned in the 11 o'clock and the 1 o'clock positions . (See Figure A7-17.5.) Positioning the canister in this manner eliminates the need to seal the canister or hoses as described above . 7-105 SECTION 8 - TRANSMISSION TRANSMISSION GENERAL DESCRIPTION The transmission (Figure 8-1) is mounted behind the engine. Its function is to convert the power output of the engine into usable power for the drive wheels of the motor home. By activating different gears within the transmission, the speed at which the output shaft of the transmission turns in relation to the speed of the engine crankshaft can be changed to meet the different driving load conditions. NOTE: The 350C transmission has been replaced in production with the 400 Series transmission, effective 1986 on G-Series vehicles. MODELS 350C AND 400-475 SERIES Chevrolet motor homes are equipped with one of two different automatic transmissions, the 350C (G-Series) and the 400-475 (P-Series). Both are fully automatic units which use a three-element hydraulic torque converter . The 350 automatic transmission, in addition to the torque converter, uses two planetary gear sets. Four multipledisc clutches, two roller clutches, and an intermediate overrun provide the friction elements required to obtain the desired function of the two planetary gear sets. The 400-475 automatic transmission uses a compound planetary gear set along with the torque converter . Three multiple-disc clutches, one gear unit, one roller clutch, and two bands provide the friction elements required to obtain the desired function of the compound planetary gear set. The three-element torque converter consists of a pump or driving member, a turbine or driven member, and a stator assembly. It is filled with fluid and is attached to the engine crankshaft at the flywheel (or flexplate). The torque converter, which always rotates at engine speed, couples the engine to the planetary gears through the fluid and provides hydraulic torque multiplication when required . Automatic transmissions replace the standard clutch and transmission . After starting the engine with the selector lever in "P" (Park) or ";N" (Neutral) position, select the range desired and press the accelerator . All automatic transmissions are equipped with a starter safety switch , designed to permit starting the engine only when the transmission selector is in the "P" or "N" position. For additional engine braking effect, as is sometimes needed in mountainous driving, place the transmission in a low range (LOW 1 or LOW 2) . LOW 2 - This range is used when extra performance is required for hill climbing or it can also be used to provide "engine braking" to slow the vehicle when going down medium grades. The shift lever may be moved from "D" to "2" (and vice versa) under most driving conditions . TRANSMISSION ASSEMBLY DETENT VALVE/SOLENOID LEVER (MANUAL LINKAGE CONTROL) Figure 8-1 - Automatic Transmission - Typical SECTION 8 - TRANSMISSION LOW 1 - This position is used to provide maximum engine braking when driving down very sharp grades or when maximum performance is required to climb a steep hill or run through deep snow or mud. You may shift into "1 " at any speed but the transmission will not go into LOW until vehicle speed is under approximately 40 MPH. VACUUM MODULATOR SYSTEM A vacuum modulator is used to automatically sense any change in torque input to the transmission . The vacuum modulator transmits this signal to the pressure regulator, which controls line pressure, so that all torque requirements of the transmission are met and smooth shifts are obtained at all throttle openings . CAUTION : TO REDUCE THE RISK OF PERSONAL INJURY, BEFORE GOING DOWN A STEEP OR LONG DOWNSHIFT (DETENT) CABLE SYSTEM GRADE REDUCE SPEED AND SHIFT THE TRANSMIS- 350C TRANSMISSION - G-SERIES SION TO A LOWER GEAR. DO NOT HOLD THE BRAKE PEDAL DOWN TOO LONG OR TOO OFTEN WHILE The detent valve is activated by the downshift (detent) cable which is connected to the carburetor linkage . When GOING DOWNHILL . THIS COULD CAUSE THE the BRAKES TO GET HOT AND NOT WORK AS WELL. AS ing throttle is half open, the detent valve is actuated, causa part throttle downshift at speeds below 50 MPH . A RESULT, THE VEHICLE WILL NOT SLOW DOWN AT When the throttle is fully opened, the detent valve is THE USUAL RATE. FAILURE TO TAKE THESE STEPS actuated causing the transmission to downshift . The COULD RESULT IN LOSS OF VEHICLE CONTROL . 3-1 detent downshift may be obtained when vehicle speed is approximately 6 to 12 MPH below the maximum throttle 1-2 upshift point . The 3-2 detent downshift may be obtained when vehicle speed is,approximately 4 to 8 MPH TORQUE CONVERTER CLUTCH below the maximum throttle 2-3 upshift point . A torque converter clutch assembly is also used on some models . The converter clutch is splined to the turbine assembly, and when operated, applies against the converter DETENT DOWNSHIFT ELECTRICAL cover providing . a mechanical direct drive coupling of the engine to the planetary gears. Converter clutch operation CIRCUIT-400-475 SERIES TRANSMISSION is determined by a series of controls and by drive range The detent solenoid is activated by an electric switch on selection . The transmission must be in drive range, and the accelerator linkage . When the throttle is fully opened, the vehicle must have obtained a preset speed depending the switch is closed, activating the detent solenoid and causing the transmission to downshift for passing speeds . on the engine and transmission combination . Aside from the torque converter, the hydraulic system within the transmission is pressurized by a gear-type pump and provides the working pressure required to operate the friction elements and automatic controls. The switch has a two-wire connector and is mounted on a metal bracket under the dashboard to the left of the steering column above the driver's left foot . (Figure 8-2 shows a typical detent downshift switch except the switch has been rotated 90 degrees counterclockwise to allow a better view of the activating plunger .) CONTROLS For proper operation of the transmission, certain controls from outside of the transmission are required. These include : 1 . Manual Linkage - To select the desired operating range, 2. Engine Vacuum - To operate the vacuum modulator . 3. Downshift Control " Cable to operate the detent valve (350C). " Electrical circuit to operate the detent solenoid (400475 Series) . MANUAL LINKAGE The manual linkage is connected between the selector lever on the steering column, and the transmission . It is through this linkage that the vehicle driver can control the transmission operating range. 8-2 A - Plunger B - Cente Side C - 2-Wire Connector P-SERIES Switch rotated 90° Counterclockwise Figure 8-2 - Detent Switch (THM 400-475 Series) SECTION 8 - TRANSMISSION To adjust the switch : FLUID LEVEL AND APPEARANCE When checking the fluid level, follow the appropriate procedure listed below. It is also important to know what appearance the fluid should have. Many times a transmission malfunction can be traced to an incorrect fluid level or improper reading of the dipstick . A fluid level which is too high or too low can cause overheating and clutch plate damage . In addition, overheating can be caused by excessive clutch plate slippage which can result from improperly installed plates, an out-of-adjustment selector linkage or the manner in which the vehicle is operated . 2. Press the accelerator pedal down to the "wide open" The type of transmission fluid that is now being used may throttle position and the switch will "self-adjust" by appear to be darker and have a stronger odor . This is snapping back into position. When adjusted, the center normal, and not a positive sign of required maintenance slide will be visually protruding out of the top of the or transmission failure. switch (more than 1-1/4 inches as in Step 1). 1 . Preset the switch by pressing the plunger and/or movable plastic center slide downward as far as possible . In the preset position, the movable plastic center slide of the switch will snap down out of position and the center slide will be nearly flush with the top of the switch . Check the portion of the slide protruding from the bottom of the switch . The slide should extend approximately 1-1/4 inches in the reset position. The switch has been designed so that the switch contacts close (make contact) when the accelerator pedal is at or nearly at the floor. If the switch contacts do not close, too much carpet padding may have been installed by the RV manufacturer preventing the pedal from reaching the floor allowing the switch contacts to close . When the dipstick is removed, note whether the fluid is devoid of air bubbles or not. Fluid with air bubbles is an indication of an air leak in the suction lines, which can cause erratic operation and slippage. Water or ethylene glycol antifreeze in the fluid gives a milky, gray or pink cast to the fluid and can cause spewing of fluid from the Disconnect the two-wire connector and check if the con- transmission breather . Coolant in the fluid, whether water tacts close at "wide-open throttle." Use an ohmmeter or or antifreeze, can cause damage to the nylon parts or continuity checker. With the continuity checker or ohm clutch plates in the transmission . If the fluid becomes conmeter in position, depress the accelerator to the floor (with taminated with coolant, the most common cause is a leakthe engine off) to verify proper switch operation . If the ing transmission cooler core. In addition to finding and contacts do not close, check to see if too much padding fixing the leak, the transmission should be disassembled, has been installed. Either remove the excess carpet pad- cleaned and the clutch plates replaced with new ones. ding or "build up" the diameter of the switch plunger. To "build up" the diameter of the switch plunger (allowing additional switch movement), install a piece of scrap 3/8inch hose over the switch plunger. If the switch contacts still do not close, replace the switch (GM Part No. Glycol test kits on the market can be used to detect antifreeze in the transmission fluid. While generally reli1242101) . Recheck and install the two-wire connector. able, certain kits may produce positive test results because of additives used in some transmission fluids . The kit manufacturer's instructions should be followed closely. MAINTENANCE AND INSPECTION The automatic transmission fluid level should be checked regularly (at each engine oil change) and changed at the intervals recommended in the Maintenance Schedule for your vehicle. Typically, the recommended interval for Capacity changing the fluid and service screen is every 24,000 miles (Heavy-Duty Emissions equipped vehicles) or every The fluid capacities of both transmissions are listed in the 12,000 miles if the vehicle was subjected to severe use. Lubrication section of this manual . To bring-fluid level from "ADD" mark to "FULL" mark requires one pint of fluid. Fluid level should be checked at every engine oil change . In addition, the fluid cooler lines, electrical lines, vacuum lines, control linkage and transmission should be checked periodically for leaks, damage or deterioration . Fluid level should be at the "FULL" mark with transmission fluid at normal operating temperature of 180°F. With fluid NOTE : Transmission conditions can be the result of poor at room temperature, 70°F, level will be between the two engine performance. If the engine - requires a dimples on the dipstick . The normal operating temperature tune-up, this should be done before checking the is obtained only after at least 15 miles of highway-type transmission . driving. (See Figure 8-3.) SECTION 8 - TRANS MISSION COOL (65*-85*F) the fluid, producing aeration which reduces the fluid's cooling effectiveness . Slippage and transmission failure can result. HOT (180°F) ADD 5 LITER (1 PT) O Fluid level that is too low can result in transmission charging pump cavitation, a loss of main and lubrication fluid pressure and clutch plate damage . It can cause slipping, particularly when the transmission is cold or the vehicle is on a hill . FULL HOT WARM Check the transmission fluid level with the engine running, the shift lever in PARK, and the vehicle level . NOTE: DO NOT OVERFILL . IT TAKES ONLY ONE PINT TO RAISE LEVEL FROM "ADD" TO "FILL" WITH A HOT TRANSMISSION . If the vehicle has recently been operated for an extended period at high speed or in city traffic in hot weather or the vehicle is being used to pull a trailer, an accurate fluid level cannot be determined until the fluid has cooled down, usually about` 30 minutes after the vehicle has been parked . Figure 8-3- Transmission Dipstick-Fluid Levels at Varying Temperatures Remove the dipstick and touch the transmission end of the dipstick cautiously to find out if the fluid is cool, warm or hot . Checking and Adding Fluid TRANSMISSION AT OPERATING TEMPERATUREThe automatic transmission is designed to operate at the "FULL HOT" mark on the dipstick at normal operating temperatures of about 180°F and should be checked under these conditions. The normal operating temperature is obtained only after at least 15 miles of highway-type driving . Wipe the dipstick clean and reinsert it until the cap seats. Remove the dipstick and note reading . 1 . If the fluid feels cool, about room temperature (65°85°F), the level should be between the two dimples below the "ADD" mark. 2 . If it feels warm, the level should be close to the "ADD" mark (either above or below) . CAUTION : WITH NORMAL OPERATING TEMPERATURES, THE DIPSTICK WILL BE EXTREMELY HOT TO TOUCH . USE CARE TO AVOID BURNS. 3. If it feels hot (cannot be held comfortably), the level should be between the "ADD" and "FULL" marks. To determine proper level, proceed as follows : 1 . Apply the parking brake and block the vehicle wheels. Changing Fluid 2.. With the selector level in the PARK position, start the engine . DO NOT RACE ENGINE . Move the selector lever through each range. 1 . Raise the vehicle . 2. With a drain pan placed under the transmission pan, remove the pan attaching bolts from the front and side of the pan . 3. Immediately check the fluid with the selector lever in PARK, engine running at SLOW IDLE and the car on a LEVEL surface . The fluid level on the dipstick should be at the "FULL HOT" mark. 3. Loosen pan rear attaching bolts approximately four (4) turns . 4. Carefully pry the transmission pan loose, allowing the fluid to drain . 4. If additional fluid is required, add sufficient fluid to bring the level to the "FULL HOT" mark on the dipstick . . Remove the remaining bolts and remove the pan and gasket. TRANSMISSION AT ROOM TEMPERATURE (65° to 85°F) - Automatic transmissions are frequently overfilled because the fluid level is checked when the fluid is cold and the dipstick indicates fluid should be added. However, the low reading is normal since the level will, rise as the fluid temperature increases (Figure 8-3). A level change of over 3/4 inch will occur as fluid temperature' rises from 600 to 180*F. 6. Drain the fluid from the pan . Clean the pan with solvent and dry thoroughly with clean compressed air. 7. Remove screen/filter and gasket . 8 . Paper or felt-type filters should be replaced . Overfilling can cause foaming and loss of fluid through the vent. With too much fluid, the rotating members churn 8-4 9. Install, as required, a new gasket or O-ring onto the screen/filter assembly. Lubricate 0-rings with petrolatum. SECTION 8 TRANSMISSION 10. Install a new gasket on the pan and install the pan. Torque the attaching bolts to 13 ft. lbs. (350C transmission), 12 ft. lbs. (400-475 transmission) . 11 . Lower the vehicle and add- the proper amount of DEXRON IIE® automatic transmission fluid through the filler tube . 12. With the selector lever in PARK position, apply the parking brake, start the engine and let idle (carburetor off fast idle step) . DO NOT RACE ENGINE . 13. Move the selector lever through each range and, with the selector lever in PARK range, check fluid level. 14. Add additional fluid to bring the level between the dimples on the dipstick (cool level) . SELECTOR LEVER RETAINER AUTOMATIC TRANSMISSION MANUAL LINKAGE When the manual linkage (Figure 8-4) is properly adjusted, the engine will start in the PARK and NEUTRAL positions only. The selector lever and manual linkage should move freely and not bind . Also, the pointer on the indicator quadrant should line up properly with the range indicators in all ranges. FRAME ASSEMBLY ROD SPRING WASHER SCREW Check the linkage to be sure that the connections are CROSS SHAFT secure and that there is no binding . If there are indications SWIVEL that the linkage needs adjustment, take the vehicle to a NOTE: 1991-94 uses a cable shift. qualified shop for service . If the linkage is not adjusted properly, an internal leak could occur at the manual valve Figure 8-4-Transmission Manual Linkage-Typical which could cause a clutch and/or band failure . COOLER LINES If replacement of transmission steel tubing cooler lines (Figure 8-5) is required, use only wrapped and brazed steel tubing meeting GM specifications 123M or equiva,lent. DO NOT USE COPPER OR ALUMINUM TUBING TO REPLACE STEEL TUBING . These materials do not have satisfactory fatigue durability to withstand normal vehicle vibrations . Steel tubing should be flared using the double flare method. ENGINE RADIATOR TRANSMISSION OUTLET PIPE TRANSMISSION MOUNT A loose transmission mount can cause a vibration in the driveline . To check for this condition, push up and pull down on transmission tailshaft while observing the transmission mount . If rubber separates from the metal plate of the mount or if the tailshaft moves up but not down (mount bottomed out), replace the mount. If there is relative movement between a metal plate of the mount and its attaching point, tighten the screws or nuts attaching the mount to the transmission or cross member (Figure 8-1) . TRANSMISSION SHIFTING If problems are encountered with the transmission shifting (upshift or downshift), refer to the appropriate shop manual for the diagnosis and adjustment procedures, or take the vehicle to a qualified service shop. FRONT COOLER LINES INLET PIPE NOTE: Depending on model year, cooler lines will enter the radiator from the left or the right side. Figure 8-5 - Automatic Transmission Cooler Lines-Typical SECTION 8 TRANSMISSION ENGINE/TRANSMISSION TORQUE CONVERTER/CLUTCH BALANCING The engine, torque converter, clutch cover or flywheel are balanced individually and are normally good for the life of the vehicle . Occasionally two or more components can be assembled with an imbalance problem and actually end up "working against each other" to create a lessthan-desirable running condition . Or, a vehicle may be acceptable as produced, but after the clutch or transmission has been repaired a vibration may surface . This is especially true with some used or non-GM rebuilt parts . An engine balance problem may exist if the vibration is present at a given engine RPM with the transmission in NEUTRAL and the wheels are not turning . If diagnosis indicates that there is an engine and/or flywheel torque converter imbalance problem, the engine and torque converter can be balanced in the vehicle using the following procedure . If the engine is equipped with an automatic transmission : 1 . Remove the flywheel cover. 2. Reposition the converter in each attaching position on the flywheel and evaluate the vibration in each position . If there is no reduction in vibration, proceed to Step 3. 3. Remove a converter to flywheel bolt and add balance weight by installing a longer bolt with several flat washers under the head of the bolt. Determine ifthe vibration is more or less severe. The vibration should be appraised by moving the longer bolt and washers to each position possible. 4. Install the bolt and washers in the position which creates a properly balanced situation . NOTE : It may be necessary to divide the weight between two adjacent bolts on the torque converter to obtain a proper balance . If the vehicle is equipped with a manual transmission : 1 . Place the transmission in NEUTRAL with the clutch engaged and increase the engine speed between 1,000 and 3,000 RPM . Note the degree of imbalance that occurs. 2. Place the transmission in gear with the clutch disengaged and increase the engine speed between 1,000 and 3,000 RPM . Note the degree of imbalance that occurs and compare it to the vibration which was determined in Step 1 above . 3. If a degree of imbalance is noted between Step 1 and Step 2, the clutch disc is probably causing the problem and should be replaced before proceeding. If no difference in imbalance is noted, install flat washers under the clutch pressure plate hold down-bolt following the procedure outlined in Step 3 above for the automatic transmission . NOTE: If a strobe is available, follow the same general approach as outlined in the Driveline Balance Procedure section of this manual . Position the pickup against the engine oil pan . ELECTRIC SPEEDOMETER 1991-94 The electromechanical speedometer replaces the cable driven speedometer on P - models . Components of the speedometer system includes the speedometer head, vehicle speed sensor (VSS), digital ratio adaptor controller, and the applicable wiring . The speedometer head is an electromechanical device using integrated circuits that control the air core speedometer and stepper motor odometer. The vehicle speed sensor is a permanent magnet signal generator located on the transmission output shaft . This analog signal, which is proportional to output shaft speed, is sent to the digital ratio adaptor controller. The digital ratio adaptor controller (DRAC) is a solid state devoce which changes the analog signal supplied by the VSS to a digital signal . This digital signal is then fed to the speedometer . The digital ratio adaptor controller is matched to the final drive of each vehicle . If the final drive ratio is changed (including tire size) for any reason, the DRAC must also be changed to match . This will ensure accurate speedometer readings . The parts book lists DRAC's (or Buffers) for a variety of tire sizes and rear axle ratios . Also, an incorrect DRAC will affect the Electronic Control Module (ECM), and the cruise control module . 1991-1994 4L80EHD Effective with the 1991 model, the Class A motor home incorporates a 4-speed electronic shift overdrive transmission . SECTION 8 TRANSMISSION THE BENEFITS OF ELECTRONIC CONTROLS A TRANSFORMATION IN TRANSMISSION TECHNOLOGY In traditional, hydraulically controlled transmissions, the gear shifts are controlled by the opposing pressures of hydraulic fluid in a complex system of spring-loaded valves . In the new, electronically controlled Hydramatic 41_80-E transmission, gear shift points and shift feel are determined by electrical signals sent from the Powertrain Control Module. The Powertrain Control Module processes data every 25 milliseconds from sensors based on throttle position, vehicle speed, gear range, altitude, temperature, engine load, and other inputs . Using this data, a signal is transmitted to the valve body Shift Solenoids, which activate the shift valves for precise shift execution. Shift points are thus precisely controlled and are identical from vehicle to vehicle. Shift feel is also electronically controlled by the Powertrain Control Module. It sends signals to the Force Motor Solenoid, which controls fluid line pressure and determines how firm the shifts will feel . The Powertrain Control Module makes the Hydramatic 41_80-E an "intelligent" transmission which senses and adapts to changes in altitude, engine load, and other conditions . Electronic controls also eliminate the need for governor and modulator systems, which significantly reduces the mechanical complexity of the transmission . GENERAL DESCRIPTION The HYDRA-MATIC 41_80-E is an electronically controlled four-speed rear wheel drive automatic transmission . It consists primarily of a torque converter and three planetary gearsets. Five multiple disc clutches, one sprag, two roller clutches, and two bands provide the friction elements required to obtain the desired function of the planetary gearsets. A hydraulic pump and an electronically controlled valve body is used to operate the various systems contained within the transmission . The torque converter contains a pump, a turbine, and a clutch pressure plate splined to the turbine. The torque converter acts as a fluid coupling to smoothly transmit torque from the engine to the transmission . It also hydraulically provides additional torque multiplication when required . The clutch pressure plate, when applied, provides a mechanical "direct drive" coupling of the engine to the transmission . The three planetary gearsets provide the four forward ratios and reverse. Changing of the gear ratios is fully automatic, mainly in relation to throttle opening and vehicle speed . The Powertrain Control Module (PCM) [or Transmission Control Module (TCM) on some applications], an on board computer, receives and processes input signals from various sensors on the vehicle and delivers output signals to the solenoids located in the control valve assembly . The solenoids control the transmission operating pressures, upshift and downshift patterns and torque converter clutch (TCC) operation . Hydra-matic 41_80-E Transmission Specifications Transmission Type 41_80-E =,4-Speed, Longitudinal Mount, High Torque Capacity, Electron ical ly' Control led Automatic Overdrive with Torque Converter Clutch Assembly Control Systems ' Shift Pattern - Solenoid Control Shift'Quality - Force Motors Control ' Torque Converter Clutch - Pulse Width Modulated Solenoid Control Gear Ratios 1st 2nd: 3rd : 4th : Rev : 2.482 1 .482 1,000 0.750 2.077 Maximum Gross Vehicle Weight 7,484 kg (16,500 lb) Maximum Gross Combined Vehicle Weight 9,072 kg (20,000 lb) Transmission Fluid Type Dexron IIE Transmission Fluid Capacities Bottom Pan Removal : 7.31_( 7.7 qt) Dry: 12 .81_ (13 .5 qt) 7 Position Quadrant (P,R,N,OD,D,2.1) SECTION 8 TRANSMISSION EXPLANATION OF GEAR RANGES The transmission can be operated in any one of the seven different positions shown on the shift quadrant . P - Park position enables the transmission output shaft to be locked, preventing the vehicle from rolling either forward or backward. For safety reasons, the vehicle parking brake should be used in addition to the transmission "Park" position . Park position should not be selected until the vehicle has come to a complete stop . The engine may be started in the Park position. R - Reverse enables the vehicle to be operated in a rearward direction . N - Neutral position enables the engine to start and operate without driving the vehicle . If necessary, this position should be selected to restart the engine while the vehicle is moving . r D - Overdrive range should be used for all normal driving conditions for maximum efficiency and fuel economy . Overdrive range allows the transmission to operate in each of the four forward gear ratios . Downshifts to a lower gear, or higher gear ratio, are available for safe passing by depressing the accelerator or by manually selecting a lower gear with the shift selector. It is not recommended to operate the transmission in overdrive range when pulling heavy loads or driving on extremely hilly terrain . Under such conditions that put an extra load on the engine, the transmission should be driven in a lower manual gear selection for maximum efficiency. D - Manual Third can be used for conditions where it may be desirable to use only three gear ratios . These conditions include towing a trailer and driving on hilly terrain as described above . This range is also helpful for engine braking when descending slight grades . Upshifts and downshifts are, the same as in Overdrive range for first, second and third gears except that the transmission will not shift into fourth gear. 2 - Manual Second adds more performance for congested traffic and hilly terrain . It has the same starting ratio (first gear) as Manual Third but prevents the transmission from shifting above second gear. Thus, Manual Second can be used to retain second gear for acceleration and engine braking as desired . Manual Second can be selected at any vehicle speed. If the transmission is in third or fourth gear when Manual Second is selected it will immediately shift to second gear. 1 - Manual First can be selected at any vehicle speed. If the transmission is in third or fourth gear it will immediately shift into second gear. When the vehicle speed slows to below approximately 56 km/h (35mph) the transmission will then shift into first gear. This is particularly beneficial for maintaining maximum engine braking when descending steep grades . 1994 BRAKE/TRANSMISSION SHIFT INTERLOCK An improved safety feature inhibits the operator from moving the shift selector lever and the transmission out of "Park" unless the brake pedal is depressed . A solenoidactuated plunger will interface with the steering column mounted transmission-shift lever which remains in a lockout position until the vehicle brake is applied . The solenoid will be energized through the brake switch and allow the shift lever to move from the park position . SECTIONS - TRANSMISSION BUSHING E BUSHING E CABLE ASH F CABLE ASH F BOLT/SCREW BOLT/SCREW COTTER PIN--/ ` WASHER ADJUSTMENT AT STEERING COLUMN ADJUSTMENT AT STEERING COLUMN & C7P -C7P TRANSMISSION SHIFT CABLE 1991-1994 Part #156443445 ADJUSTMENT AT TRANSMISSION AUTO TRANS SHIFT LEVER & CABLE INSTALLATION & ADJUSTMENT 1 . With trans selector shaft (A) in Neutral, align lever ASM (B) with flats on shaft (A) . 5. With steering column shift lever in neutral attach link (D), bushing (E) & cable ASM (F) as shown. slot on 6. With trans lever ASM (B) in neutral position install and adjust clevis (G) for free pin (H). 2. Push lever ASM (B) on to shaft (A) far enough to engage retaining nut (C) . CAUTION : Do not drive lever ASM (B) on to trans selector shaft (A) by hammering or bumping, as internal components of transmission will be damaged . 3. Hold lever ASM (B) & hand tighten retaining nut (C) to 20-27 N"m torque . 7. Install clevis pin (H) & secure with cotter pin (J) . 8. By moving steering column shift lever through full range check for positive detent engagement at trans for each position . 9. Readjust clevis (G) if necessary, for positive detent engagement. CAUTION : Do not apply torque in excess of 27 N"m, as damage to selector shaft may occur. 4. Move lever ASM (B) (selector shaft) by hand through NOTE: Do not use trans cable adjustment to adjust detent range positions to check for freedom from bindPRNDL alignment (see UPC 9A/07-04-03 for ing & positive detent engagement. PRNDL asjustment procedure). APPENDIX 8-1 TRANSMISSION FLUIDS AND COOLER TIPS OIL TEMPERATURE MEASURED AT CONVERTER OUTLET TO COOLER 350°F is the maximum temperature . This is the normal place to install a temperature gage or signal . The temperature in this location will vary significantly with each vehicle start-up or hill. If the temperature reaches 350°F, reduce throttle. To lower the transmission temperature with the transmission in NEUTRAL, run the engine at 1,200 RPM for 2-3 minutes to cool the oil . Do not allow the converter outlet temperature to exceed 350°F . Keep a close check to prevent the engine cooling system from overheating . 350°F or higher would be typical of rocking the vehicle in mud, snow, or sand, or a transmission in stall (full throttle, no vehicle movement) . When the transmission is in stall, the transmission will develop heat at a rate of one degree per second of stall. OIL TEMPERATURES MEASURED IN THE SUMP OR OIL PAN DEGREES F MILES 175 100,000 195 50,000 212 25,000 235 12,000 255 6,000 275 3,000 295 1,500 315 750 335 325 355 160 375 80 390 40 150°F - Minimum operating temperature for continuous 415 Less than 30 Minutes operation . It is possible in low ambient temperature to overcool the transmission with oil to air-type coolers ; it is Figure A8-1-1 -Transmission Fluid hard to overcool if used in conjunction with oil to water Life Expectancy/Temperature coolers installed in most standard automotive radiators . Relationship This information shows why the various maintenance 190°-200°F- Proper oil level checking temperature . change intervals and/or oil coolers are recommended for severe usage . 200°F - Maximum oil level checking temperature . Beyond this, readings are not reliable because of expansion . NOTE : THE ABOVE' CHART IS BASED ON THE ASSUMPTION THAT OIL TEMPERATURE RE285°F - Maximum sump/oil pan temperatures for short MAINS CONSTANT FOR THE MILES duration, such as a long hill climb . INDICATED . TEMPERATURES WHICH APPEAR FOR SHORT PERIODS, SUCH AS 300°F- Metal parts inside the transmission begin to warp CLIMBING HILLS, ETC., WOULD NEED TO BE and distort in varying degrees, seals melt rapidly, and AVERAGED AGAINST NORMAL OPERATING transmission fluid life is extremely short due to oxidation TEMPERATURES TO DETERMINE ACTUAL and distress . LIFE EXPECTANCY . AUTOMATIC TRANSMISSION FLUID OXIDATION Automatic transmission fluid can provide up to 100,000 miles of service before oxidation occurs under normal operating temperaturesof about 170°F. Above normal operating temperatures, the oxidation rate doubles (useful life of the fluid is cut in half) with each 20 degree increase in temperature . The approximate life expectancy at various temperatures is as follows : AUTOMATIC TRANSMISSION FAILURE IMMEDIATELY AFTER SERVICING If there was no known prior abuse, the new transmission fluid is not at fault. What has probably happened is that a certain amount of highly oxidized fluid remained in the transmission converter and cooler lines. The old fluid and new fluid will not mix. They settle out as sludge or varnish, causing valves to stick and/or plug oil passages and screens . When this happens, the transmission may malfunction or fail completely. The best way to prevent the problem is to follow the manufacturer's drain intervals for severe operating conditions such as trailer towing, mountain driving, and stop-and-go city driving . APPENDIX 8.1 TRANSMISSION FLUIDS AND COOLER TIPS (Cont'd) AUTOMATIC TRANSMISSION FAILURE IMMEDIATELY AFTER OVERHAUL Assuming proper workmanship and assembly, failure can often be caused by metal particles or debris trapped in the cooler circuit . Unless the converter, cooler, and cooler lines are thoroughly flushed during overhaul, the leftover contaminants will return through the cooler return lines to the transmission lube supply and may cause a second failure . To prevent this, be certain all the transmission components, cooler lines, and cooler are cleaned prior to reassembly. DO NOT TAKE SHORTCUTS . DEXRON IIE® VERSUS TYPE F TRANSMISSION FLUID Type F fluid must never be used where Dexron II® is specified . The difference in the fluids relates to their friction properties . GM transmissions are designed to shift smoothly which requires a low-static fluid such as Dexron IIE®. On the other hand, transmissions that require Type F transmission fluid are designed to shift more harshly, providing more shift feel. Type F fluid is a highly static fluid, . and provides more friction than Dexron IIE®. If Type F fluid is used in a GM-designed transmission, shifting will become more harsh . In turn, harsh shifts apply higher shock loads to components that weren't designed for high-shock loads, and transmission failure is almost certain . DEXRON IIE ® FLUID COLOR CHANGE AND STRONG ODOR These two "tests" are no longer satisfactory criteria for recommending a fluid drain and refill . With the Dexron II© Figure A8-1-2- Deaeration Cooling System fluid, rapid loss of the red color and darkening of the new fluids are normal and DO NOT affect their performance. Contrary to past performance, the service technician should not consider a dark appearance or burnt odor as the signal to change fluid. The only accurate method for determining a fluid's serviceability or effectiveness is through a laboratory analysis . Short of a laboratory analysis the owner's manual drain recommendation should be followed. INSTALLATION OF A MANUAL WATER SHUT-OFF VALVE IN THE HEATER LINE DO NOT install a manual water shut-off valve in the heater line. The heater water return is routed to the radiator outlet tank and continuous coolant flow is necessary to control oil temperatures during closed thermostat (warm-up) operation . (See Figure A8-1-2.) Shutting off this portion of the heater flow destroys the engine's deaeration system and may result in premature engine or transmission failure . A transmission warms ;up faster than the engine and it is not advisable to have the radiator transmission oil cooler exposed to air . A bubble cavitating in the engine water pump could cause engine hot spots. A water shutoff valve is permissible in the rear seat heater line. ADDING AN EXTERNAL FLUID COOLER Before adding an external fluid cooler consideration should be given to many factors : " Initial cost " Need " Potential extra leak points (For example : A tee added into the line is not one leak potential but three. A coupling provides two leak point possibilities - the cooler has two ends plus the cooler itself .) " Lines, have potential for fatigue and rubbing or chafing " Quality of the installation . The transmission dipstick itself might be considered a major factor for adding an external cooler . Current dipsticks have several dots at the low end of the operating range that would show a ,valid fluid level if checked cool at 65°-85°F . (See Figure A8-1-3 .) This low reading is normal since the level Will rise as the fluid temperature increases . A level change of over 3/4 inch will occur as fluid temperature rises from 60° to 180°F. If starting with the lower dot and, after driving, the level did not go over the maximum high of the hash marks, an extra cooler would be difficult to justify . For this condition, all that's needed is to consider fluid and filter change intervals per the owner's manual dealing with severity of service . If in doubt, change the fluid and filter . If after heavy driving or trailer pulling,the fluid level rises above the hash marks, an external cooler may remove enough. extra heat to help stay within the operating hash marks . (See Figure A8=1-3 .) 8-10 APPENDIX 8.1 TRANSMISSION FLUIDS AND COOLER TIPS (Cont'd) COOL HOT WARM NOTE: DO NOT OVERFILL . IT TAKES ONLY ONE PINT TO RAISE LEVEL FROM "ADD" TO "FULL" WITH A HOT TRANSMISSION . With fluid coolers, the hot oil enters the bottom of the cooler and the cooled fluid exits out of the top of the cooler for better heat dissipation . This is the reverse of the engine radiator . (See Figure A8-1-4.) Overfilling can cause foaming and loss of fluid through the vent. With too much fluid, the gearing "churns" the fluid and produces aeration and foam, and reduces the fluid's cooling effectiveness . Slippage and clutch failure often result. A low fluid level can result in causing pump cavitation and loss of main and lubrication oil pressures . This can result in slipping and clutch damage, particularly when cold or when on a hill. Figure A8-1-3-Fluid Levels at Varying Temperatures TRANSMISSION NOTE: DEPENDING ON MODEL YEAR, COOLER LINES WILL ENTER THE RADIATOR FROM THE LEFT OR THE RIGHT SIDE. FRONT FLUID COOLER LINES Figure A8-1-4-Typical Oil Cooler Lines NOTE: After-market transmission temperature gage should be installed in the lower (hot) oil line as viewed from entering the radiator . After-market external oil to air cooler should be installed after the GM transmission cooler. The,lower (hot) line should go first into the lower fitting of the GM radiator cooler then out from the top fitting to the after-market oil to air cooler. Extreme cold weather may require the after-market oil to air cooler be covered so not to cool the oil to much . After-market external filter should be installed in the lower (hot) oil line to prevent any debris from reaching the radiator cooler if the filter is being installed in conjunction with a transmission failure or overhaul . APPENDIX 8-2 TEMPERATURE MONITORS The following information has been provided as an aid to the motor home owner. Features, specifications and ordering information have been provided. Tempilabels temperature monitors are extremely useful in monitoring the safe operating temperature of equipment such as gear boxes, transmission pans; radiators, the engine oil pan, heat exchangers, etc . Tempilabels are selfadhesive temperature monitors consisting of one or more heat-sensitive indicators sealed under transparent heatresistant "windows ." (See Figure A8-2-1 .) The centers of the indicator circles turn black at the temperature rating shown on the label . The color changes are irreversible and provide a temperature history of the surface being monitored . The Tempilabel can be removed and attached to a service record to provide a permanent service history . The Tempilabel temperature monitor indicates a specific temperature or sequence of temperatures with a tolerance of one percent of the respective rating (plus or minus) . The performance of the Tempilabel temperature monitor is not affected by transient contact with contaminants such as solvents, gasoline, fuel oil, lubricants, hot water or steam . To use the Tempilabel, remove the film backing to expose the adhesive . Press the Tempilabel firmly to the desired work surface . No special treatment to the work surface is necessary although it should be clean to obtain maximum_ contact and adhesion . Sample of product and listing of one of several series available is shown as Figure A8-2-1 . Tempilabels are sold at nominal cost for a minimum order of 10. Part No. Series AA/4A/4B/4C-Tempilabel® NOTE: ACTUAL DIMENSIONS ARE 1-3/4-INCHES LONG AND 7/8-INCH HIGH. THE INDICATING WINDOW IS 7/32-INCH IN DIAMETER . . Figure A8-2-1- Typical Tempilabel Series 4A-100 4A-110 4A-120 4A-130 4A-140 4A-150 4A-160 4A-170 4A-180 4A-190 4A-200 4A-210 4A-220 4A-230 4A-240 4A-250 4A-260 4A-270 Temperature Ratings 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 FOR FURTHER INFORMATION : TEMPIL COMPANY HAMILTON BOULEVARD SOUTH PLAINFIELD, NEW JERSEY 07080 (201)757-8300 130°F 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 APPENDIX 8-3 GEARED ROAD SPEED DETERMINATION Geared road speed is the maximum theoretical speed of a vehicle based on engine RPM, transmission and axle gear ratios, and tire size. In actual use the vehicle may or may not have enough horsepower to attain this speed. To determine geared road speed the formula is as follows : RPM x 60 GEARED ROAD SPEED = R x, M RPM = Engine speed at selected Net Horsepower. (To determine maximum geared road speed use engine RPM where maximum horsepower is developed .) R = Ratio. Transmission gear x axle ratio = R M = Tire revolutions per mile. Example : A truck with 8-19.5 tires (613 revolutions per mile) . 5.83 axle ratio, 4.8 liter (292) engine (3,400 RPM) NOTE: See the Wheel and Tire section of this manual for typical motor home tire revolutions per mile . 3,400 x 60 = 204,000 = 57 MPH Nonlisted tire size revolutions per mile can be ob5.83 x 613 3,574 tained from local tire dealer catalogs. AUTOMATIC Model & RPO Number 350 MXI Torque Converter Gear Ratios First Second Third Fourth Reverse 400 MXI Lockup Breakaway 2.52 1 .52 1 .00 1 .94 5.29 3.19 2.10 4.07 475 MXI 700R4 MXI 41_80E Lock- Breakup away Lock- Break- Lock- Breakaway up away up Lock- Breakup away 2.48 1 .48 1 .00 2.10 2.48 1 .48 1 .00 2.10 5.21 3 .11 2.10 1 .58 4:37 5.70 3.40 2.30 4.83 5.46 3.26 2.20 4.62 ' 3.06 1 .63 1 .00 .70 2.29 6 .73 3.58 2.20 1 .50 5.03 Figure A8-3-1 NOTE : Typical class A motor home will be equipped with a model 475 transmission . Typical Class C will be equipped with a 350 transmission thru 1990-1991 up both will have the 4L80E transmission . As shown in the above chart, the breakaway ratio includes the transmission torque converter ratio . For example : In the 475 transmission, the mechanical first speed gearing is 2.48 to 1 times the torque multiplication of the torque converter ratio of 2.20 to 1, which equals the breakaway ratio of 5.46 . Breakaway is shown in third gear primarily to show converter ratio . Third gear at normal road speeds can be considered a 1 to 1 ratio. NOTE: For best engine life and economy, an engine should cruise at a continuous 80 to 90 percent of rated RPM. Shift points at rated RPM are acceptable. (See Figure A8-3-2 .) Figure A8-3-2 - Engine Speed vs. Rated Life Expectancy 8-13 2.48 1 .48 1 .00 0.75 2 .08 APPENDIX 8-4 CHECKING GEAR RATIOS SINGLE DRIVE AXLES The method outlined below may be used whenever it is desirable to check or verify the gear ratio of a rear axle . Two-speed axles may be checked by repeating the procedure in both high and low axle ratios. 1 . Jack up a drive wheel on one side of the vehicle . Shift the transmission into NEUTRAL . 2. Mark the pinion flange or yoke of the drive unit at some convenient reference point . Mark the tire of the drive wheel that is off the ground . Turn this drive wheel two complete revolutions noting the number of revolutions of the marked pinion flange or yoke. The number of revolutions of the pinion flange or yoke indicates the gear ratio of this axle. For example : Two revolutions of the drive wheel and 7-2/3 (7.66) revolutions of the flange or yoke mean the gear ratio of this axle is 7.66 :1 . When only one drive wheel is free to turn, the action of the differential gear assembly requires that the drive wheel be given two complete revolutions to obtain the proper gear ratio by this method . You could expect 4 .10, 4 .56 or 4 .88 as typical Class A or C motor home axle ratios . NOTE: See the Wheel and Tire section of this manual for typical motor home tire revolutions per mile . Non-listed tire size revolutions per mile can be obtained from local tire dealer catalogs. APPENDIX A DRIVE BELTS AND TENSION SPECIFICATIONS Proper care and maintenance of drive belts is an important part of good engine maintenance . Proper belt tension and the condition of the pulley grooves are of primary concern. Since belts and pulleys wear with use, look at all frictional surface areas for signs of wear. Normal wear can be recognized as even wear, both on the belt and the grooves of the pulley . It is the unusual signs of wear that indicate some corrective action is necessary. When checking ; remember that failed or partially failed belts shown to be defective may have been damaged by a bad pulley, a misaligned drive or by some faulty mechanical component . UNUSUAL WEAR CONDITIONS FABRIC RUPTURE A fabric rupture (View 2) can be caused by operating a belt over a badly worn pulley, by too much tension which forces the belt down into the groove, or by foreign objects falling into the pulley groove while the drive is operating . COVER TEAR A tear in the cover of a belt (View 3) is normally a result of the belt accidentally coming into contact with some part of the application . It is no fault ofthe belt or its construction . Cover tears are usually caused by belts running too loosely allowing them to "throw-out" centrifugally and rub other parts of the application . Proper belt tension will prevent this from happening. NOTE : A slight raveling of the belt covering at the splice location does not indicate imminent belt failure . Simply cut off loose raveling . VIEW 1 BASE CRACKING VIEW 2 FABRIC RUPTURE VIEW 3 COVER TEAR ALI VIEW 4 SLIP BURN VIEW 5 GOUGED EDGE VIEW 6 WORN SIDES BASE CRACKING Excessive cross-checking (View 1) extending into the rubber on the base of a belt and showing little or no side wear indicates that it must be replaced . Small cracks only in the cover material do not indicate belt failure . If the belt fails after three or four seasons of use, the belt should not be classified as being defective . However, if the base of the belt also shows cross-checking, the belt has been exposed to weather to the extent that the inner fabric is beginning to rot . SLIP BURN This belt (View 4) was ruined by operating too loosely . The belt slipped under load. And when it finally grabbed, it snapped . Proper belt tension would have avoided this failure . GOUGED EDGE A gouged edge in a belt (View 5) can be caused by a damaged pulley or interference with some part of the application . Check the condition of the pulley . Make sure the belt does not rub on any part of the application while operating . WORN SIDES Badly worn belt sides (View 6) result from long operation without enough tension . The sides will be worn and slightly burned around the entire circumference . Check for proper belt tension . Also check the pulleys for incorrect alignment . APPENDIX A DRIVE BELTS AND TENSION SPECIFICATIONS (Cont'd) DEFECTIVE BELTS BELT INSTALLATION A belt that stretches excessively is one that stretches beyond the adjustment provided to take up normal belt stretch . 1 . Move the belt tension adjustment to the position where it provides the most slack . In some cases it may be necessary to remove the accessory to install the belt. EXCESSIVE STRETCH Use the following procedure when installing new belts: 2 . Examine pulleys for chips, cracks, bent sidewalls, rust, corrosion or other damage. LUMPY BELTS Lumpy belts usually occur and are more noticeable on variable speed drives and other high-speed belt installations. The result is excessive vibration . If belts are not relieved of tension while the engine or vehicle is stored, they will often cause temporary vibration upon start-up. Give them time to straighten out . 3. Check pulley alignment. 4. Place belts in the pulley grooves by hand. NOTE: Never pry or force a belt onto the pulley with a screwdriver,"crowbar, wedge, etc ., since both belt and drive can be damaged . INTERNAL CORD FAILURE BELT REPLACEMENT Failure of one or more of the internal tension cords will result in the belt rolling out of the pulley groove. Cords can be broken by prying the belt over the pulley . Here are a few service tips for replacing belts. IMPROPER LENGTH Never replace just one belt on a 2-groove, single pulley setup. It is possible that an improper length belt could accidently be installed on an engine . Always check to be certain that the belt length is correct before the belt is installed . A.I .R . PUMP (NA5 ONLY) Replace Belts In Matched Sets Never install only one belt from a different set of matched belts . Install a complete, matched belt set . BELT LASH-UP CONFIGURATIONS 1985 1/2 - CURRENT A.I .R. PUMP (NA5 ONLY) POWER STEERING PUMP A.I .R. PUMP CRANKSHAFT 3RD TRACK " 454 WITH FACTORY 454 WITHOUT AIR CONDITIONING AIR CONDITIONING NOT E: 1990 THRU 1994 - A .I .R . PUMPS WERE ELIMINATED A-2 APPENDIX A DRIVE BELTS AND TENSION SPECIFICATIONS (Cont'd) Check Condition Of Pulleys Always check the condition of pulleys before replacing belts. Inspect the pulleys for chips, cracks, bent sidewalls, rust, corrosion, etc . Replace any pulleys found to be defective . Check Pulley Alignment Misaligned pulleys result in shortened belt life. Check the alignment between pulleys as follows : 1 . Position a straightedge or cord line to touch both pulleys at all points . The shafts must be parallel . 2. Rotate each pulley a half revolution and note whether the contact of either pulley with the straightedge or cord line is disturbed . If so, this indicates a bent shaft or warped pulley . BELT TENSION ADJUSTMENT To carry their full load, belts must grip the entire area of contact with the pulley . When operated too loosely, belts can slip, heat, burn, or grab and snap. More belts fail from undertightening than from overtightening . When operated -too tightly, belts can damage the engine by causing side loading on the crankshaft, crankshaft bearings, and accessory bearings. Excess tension also stretches and weakens belts. ALL V8 ENGINES EXCEPT DIESEL Generator A.I .R . Pump P/S Pump 50 Lb. Adjust to 75 ± 5 Lbs . Used Min . Adjust to 125 ± 5 Lbs. New A/C Compressor 65 Lb. Adjust to 95 ± 5 Lbs. Used Min. Adjust to 140 ± 5 Lbs . New 6.2L - V8 DIESEL Generator P/S Pump 70 Lb . Adjust to 75 ± 5 Lbs. Used Min. Adjust to 110-140 Lbs. New A/C Compressor 80 Lb. Adjust to 90 ± 5 Lbs. Used Min. Adjust to 135-165 Lbs. New BELT TENSION CHART New drive belts will stretch after the first few hours of operation . Run the engine for 15 second's to seat the belts, then check belt tension again . Retighten fan drive, pump drive and battery-charging generator drive belts after 1/2 hour or 15 miles and again after 8 hours or 240 miles of operation . Thereafter, check the tension of the drive belts every 200 hours or 6,000 miles and adjust them if necessary . Belt tension tools are available from several tool manufacturers, as listed below: No. BT-7825 Borroughs Tool and Equipment Company 2429 North Burdick Street Kalamazoo, Michigan 49007-1897 No. 91107 Gates Rubber Company 999 South Broadway Denver, Colorado 80217 Proper Belt Tension (V-Belts) : When installing V-belts, keep the following in mind : Adjust the belt tension so that a firm push with the thumb at a point midway between two pulleys will depress the belt no more than 1/4 inch (Chevrolet engine) . If a V-belt tension gage is available, adjust the belt tension as outlined in the belt tension chart which follows . NOTE : When installing or adjusting accessory drive belts, be sure the bolts in the accessory adjusting pivot point and in the adjusting slot are tightened properly. No.J-23600 Kent Moore Tool Division 28635 Mound Road Warren, Michigan 48092 NOTE: J23600B Similar to Borroughs Gage. APPENDIX A DRIVE BELTS AND TENSION SPECIFICATIONS (Cont'd) APPLICATION CHART- BELTS & HOSES for P-30(32) Series Motor Home with 454 CID Engine Year Remarks Fan Belt, Generator Belt 1979-85 Poly V, 6 Rib 19851/2 to 55.98 inches 1989 (1422 .0 mm) 1990 (1340 mm) Year Radiator Hose GM Part No. 9433752 14087540 (Production No. & Service No.) 10085787 73-81 73-81 1982 to Current Power Steering Pump Belt 1979-85 19851/2 to Current Without A/C Without A/C .47 inch x 45.5 inches 19851/2 to Current With A/C, Hi Ride 3/8 inch x 41 inches GM Code : XL 9433745 14087507 (Production No.) 10034695 (Service No.) 14082454 (Production No.) 9433735 (Service No.) 1983 1984 Remarks Upper Hose Vertical Radiator 350 Engine 1 1/2 ID Ident 6259952 Upper Hose Vertical Radiator 454 Engine 1 1/2 ID Ident 6259953 Upper Hose Horizontal Radiator 454 Engine Varies by Model & Option Upper Hose Horizontal Radiator 6.2 Diesel Varies by Model & Option GM Part No. 6259952 6259953 14049401 15599363 15595586 14049497 1985 Upper Hose 454 Engine H4D 14049401 A.I.R. Pump Belt 85-89 Upper Hose 454 Engine H5D 15599363 19851/2 With and Without A/C 14092344 to All Federal Jobs, Hi Ride (Production No.) 1989 .47 inch x 45.00 inches 10034695 GM Code: CNA (Service No .) 90-94 Upper Hose 454 Engine H5D 15638164 73-81 Lower Hose Vertical Radiator 350 and 454 Engine 1 3/4 ID Ident 343414 Lower Hose Horizontal Radiator 350 Engine Same as 73-81 Vertical Radiator Lower Hose Horizontal Radiator 454 Engine Lower Hose Horizontal Radiator 6.2 Diesel 4.54 Gas Air Conditioning Belt (GM-ARA) 19851/2 to Current Hi Ride 3/8 inch x 60.5 inches GM Code: GA 15598439 (Production No.) 14033869 (Service No.) 1982 DO NOT USE BELT DRESSING Belt dressing is not recommended for belts at any time. Most dressings contain chemicals which tend to soften belts . While this softening process does increase the friction between the belt and pulley grooves, the result is only temporary. BELT CLEANING INSTRUCTIONS Remove all grease and oil as quickly as possible before they can penetrate the belt and cause deterioration . A-4 1982 to 1984 1982 to Current 343414 343414 14049500 15595587 14042372 14049500 APPENDIX B PREPARING THE MOTOR HOME FOR STORAGE Special consideration may be required when conditions of high humidity, extreme temperatures or outdoor storage are encountered. Local experience will dictate any Additional protective measures for such conditions. " " " " " Gasoline Engines Only - After the oil has been replaced, remove air cleaner and pour 1/2 to 1 pint of 10W or lighter oil into carburetor air intake with engine running . Pour slowly at first, then rapidly using last quarter to stall engine . Replace air cleaner . Check battery/batteries and inspect test hydrometer on Delco Freedom or maintenance-free batteries and REACTIVATING VEHICLE AFTER charge if green dot is not visible to avoid freezing and EXTENDED STORAGE deterioration . Both battery cables should be discon- " Check oil and fluid levels and replenish as necessary nected at the battery/batteries to prevent gradual disin the following components: engine, radiator, crankcharge, and the possibility of fire due to short circuits. case, transmission and differential. Check gasoline On conventional batteries, check electrolyte specific supply . If the vehicle is equipped with air conditioning, gravity and charge if below 1 .255. (See Battery Mainrefer to the procedure which follows below. tenance During Vehicle Storage section of this Appendix .) " Check under hood and under vehicle for nesting creatures and evidence of leakage of oils or fluids or physical Prior to storage, fill tank/tanks, add fuel stabilizer, damage . run engine and generator to insure stabilized fuel is circulated throughout the complete fuel system. " Inflate tires to recommended pressure. Keep chassis windows closed . Make sure all covers Clean battery end of cables and install fully charged are in place . battery . Avoid trees in parking area to eliminate potential damage from tree sap or bird droppings . Remove high weed Lubricate chassis suspension and steering growth which affects paint by attracting insects or causcomponents . ing stains . Rinse, wash and wipe horizontal surfaces of motor " Check brake operation and fluid level . Bleed and adjust brakes if necessary . home at least once per week when stored outside to remove accumulations which settle on flat surfaces . Remove spark plugs and clean and gap (gasoline Leave parking brake in "OFF" position . engines) . " Unit should be parked on level surface or with front of " Check and clean carburetor air filter assembly . chassis higher than rear if level surfaces are not available ._ This is to prevent gasoline draining into engine IF VEHICLE IS EQUIPPED WITH AIR over a long period causing possible damage to engine CONDITIONING by "hydrostatic lock" when started . " Disconnect the compressor clutch wires before at" Check engine coolant and, if necessary, increase tempting to start vehicle . antifreeze . " Check to see if compressor hub and clutch driver can Check and secure all caps to prevent water, snow and be turned by hand. If not, the unit should be broken dirt from entering engine. loose by manually turning the shaft with a wrench on the shaft lockout on the clutch driver plate . A few "rockCheck and keep tires inflated to recommended tire ing" turns should be sufficient so that the shaft can be pressure. turned by hand. Remove windshield wiper arms and blades and store *Reconnect coil wires and check belt tension . Run in vehicle . engine with air conditioning on for a minute or two to Start and run engine until completely warm . Drain enreseal system . gine oil and replace filter element, refill with fresh oil . If vehicle is equipped with air conditioning, the unit should Check the refrigerant . This can be done by checking for air bubbles in the sight glass on the top of the rebe operated during this final engine warm-up to lubricate compressor seal . ceiver-dehydrator (on vehicles so equipped) . APPENDIX B PREPARIN G THE MOTOR HOME FOR STORAGE (Cont1d) BATTERY MAINTENANCE DURING VEHICLE information in the Engine Electrical System section of this manual .) STORAGE Parasitic loads (drains) from the radio, clock, ECM, courtesy lights, and other accessories will discharge batteries in vehicles not used for an extended period of time, or especially during vehicle storage . Provisions to maintain a proper state of charge of batteries in these vehicles is necessary . The discharged batteries can freeze at temperatures as high as 32°F, resulting in permanent damage . Other permanent damage may also result to batteries allowed to stand discharged for extended periods . Disconnected batteries will also self-discharge, especially in higher ambient temperatures ; therefore, even disconnected batteries should be checked for a "green dot" every four months and recharged if necessary. In addition, any electrical connections or fuses removed or disconnected to reduce parasitic loads should be reinstalled or connected prior to reactivating the vehicle after extended storage . To alleviate battery discharge, the negative battery cable should be disconnected on vehicles which are not going to be in service within a 20-day period. If this is not pos- NOTE: The ignition switch must be OFF when connecting sible, batteries should be checked every 20-45 days, and the battery cables or a battery charger . Failure to recharged if necessary. If the "green dot" of the battery do so may overload or damage the ECM or other is not visible, then the battery must be recharged . (Check electronic components from voltage spikes which the battery maintenance and inspection procedures can occur during these operations. APPENDIX C NUT AND BOLT IDENTIFICATION The following is presented as an aid to the motor home owner in understanding some of the problems of threaded fasteners, as well as to provide information to make better, safer and more permanent repairs . " Every mechanic knows from experience that any nut or bolt can be overtightened to the point of failure . Few realize that nuts and bolts can also fail or break in service if not tightened enough . " Loose nuts result from using the wrong grade bolt as often as from undertightening . " In critical applications, standard threaded nuts used more than once can cause failure of the bolts they are installed on. " There is a right way and a wrong way to install a flat washer on a bolt. An improperly installed flat washer can cause bolt failure. (See NOTE in Washer Applications section of this Appendix .) FORCES ACTING ON NUTS AND BOLTS To understand some of the problems of threaded fasteners, it is necessary to understand several factors concerning the forces that act upon nuts and bolts as well as the properties of the materials nuts and bolts are made from. TENSION - One of the basic forces acting upon a nut and bolt is tension . Under tension, all grades of steel bolts will stretch . Up to a point (called the "yield point'), this stretching is not permanent and the bolt will return to its original dimensions once the tension has been removed . If the load is great enough to cause the bolt to stretch 2/10 of one percent of its original length, the stretching will become permanent . TENSILE STRENGTH - Once the yield point of a bolt has been exceeded, the bolt will continue to support increasing loads but it will also stretch rapidly and permanently until the tension load equals the tensile strength. Tensile strength determines the point at which a bolt will break . PROOF LOAD - Successful applications of nuts and bolts are achieved when the tension in the bolt comes as close as practical to the yield point without exceeding that point. This tension is called the "proof load"' and is the maximum load the bolt can support . TORQUE OR TORSION - It would be extremely convenient if the tension or clamping force of a bolt could be measured directly "in the field," however, this direct measurement cannot be accomplished successfully . The measurement must be made indirectly using another force that acts upon nuts and bolts. This force is referred to as torsion or torque . Torque is the twisting force that is applied to the nut and bolt during tightening . When the bearing surfaces of a nut and bolt touch the workpieces that are being fastened together, friction is generated in two places ; (1 .) at the flanks of the threads on the bolt and nut and, (2.) at the point of contact of the nut or bolt head and the workpiece . About 40 percent of the torque (or twisting force) applied to a nut or bolt being tightened is expended oveacoming thread friction while 50 percent of the torque input is lost to friction between the nut and the workpiece . This leaves 10 percent of the torque applied to new unlubricated nuts and bolts being available for bolt stretch or clamping force . WASHER APPLICATIONS Two of the most important parts of a well-engineered bolt are the washer face and the fillet where the shank of the bolt joins the head of the bolt. WASHER FACE - The washer face is the raised portion of the head that contacts the workpiece . The washer surface keeps the hex points of the bolt head from digging into the workpiece and increasing the installation torque. This prevents a false torque wrench reading which would result in an undertightened bolt . The washer surface of the bolt has the same area as the bearing surface of the nut so that friction or torque will be equal whether the nut or bolt is actually being tightened . FILLET - The fillet is the small radius or curve between the side of the shank and the washer face of the bolt. The purpose of the fillet is to reduce concentrations of stress where the bolt head and the shank of the bolt meet. A deep "scratch" in the fillet area could weaken the bolt to the point of causing the bolt head to break off under tension. One possible cause to this type of problem is the sharp edge of a drilled hole which digs into the fillet beneath the bolt head. As the sharp edge digs into the fillet, a small crack results which progresses to actual bolt failure when full tension is applied . The solution to this problem is to protect the fillet either by slightly countersinking the drilled hole to remove any sharp edge or by using a flat washer under the bolt head. NOTE: There is a "right way" as well as a "wrong way" to install a flat washer . As part of the stamping process in making flat washers, every washer has both a "sharp" side and a slightly "rounded" side . Before using a flat washer, examine the washer closely to identify which side is sharp and which is slightly rounded . The rounded side must ALWAYS be placed next to the bolt head while the sharp side must be placed against the surface of the workpiece . Failure to position a washer in this manner defeats the purpose of the flat washer . A-7 APPENDIX .C NUT AND BOLT IDENTIFICATION (Cont1d) NUT AND BOLT FAILURE Perhaps the most common cause of bolt failure is the use of too low a grade of bolt for the application . For example ; a bolt that has a yield strength too low for the forces being applied will stretch permanently and when the equipment is shut-down and the load on the bolt relaxes, the result appears to be a loose nut . A service technician who spots the loose nut is going to tighten it; however, in this case tightening the nut and bolt will not solve the problem . When the equipment is started and the load is reapplied, the bolt will stretch again. The next time the load relaxes, the nut will again be loosened . Again the service technician will tighten the nut although this time the technician will probably apply additional force. If the bolt breaks, as it usually does, it is replaced with the same grade of bolt as the original and the process repeats itself . There are several ways to avoid this cycle from occuring. They are : 1 . Drill out the hole and replace the original bolt with one of the same grade having a larger diameter. 2. Use a higher grade bolt than the original . 3 . In some cases, it may be possible to substitute a finethread nut and bolt for a coarse-thread nut and bolt of the same grade and diameter. Fine-thread bolts tend to be about 10 percent stronger than their coarsethread counterparts . Just as important as using the correct grade nut and bolt for a job is the necessity for the nut, bolt and washer to be matched to each other. If a low-grade nut is used with a high-grade bolt, it is very likely that the threads of the nut will either "strip out or freeze" to the bolt before the proper torque can be achieved . A soft flat washer used with a high-strength bolt and matching nut will have a tendency to compress or "brinnel" under specified torque settings . This situation reduces the bolt's tension and makes it subject to fatigue failure . A hardened washer is heat treated and "file hard." viding that the stretch does not exceed 2/10 percent of the grip length of the bolt, the bolt will return to its previous length when the load is relaxed . However, the ability of heat-treated bolts to withstand repeated stretching and relaxing is limited. Continuous stretching of a heat-treated bolt causes tiny cracks to form at areas where stress is concentrated . These areas can be at the root of the threads, at the fillet under the head of the bolt, or anywhere there is a surface flaw such as a nick or scratch . In time, these cracks will widen and the bolt will fail. FATIGUE FAILURES Bolts must be tightened properly to eliminate repetitive stretching problems. Correct torque must be applied so that the clamping force that is generated is greater than any load the fastened workpieces would be subjected to. Correct torque ensures that a bolt is properly "preloaded ." A pre-loaded bolt does not continually stretch and spring back, or is not subject to fatigue and/or failure . Fatigue failures can also be caused by undertightening or reusing nuts and bolts in critical applications. The nut is perhaps the most dangerous fastener to use more than one time. The reason for this is that standard nuts have to be made softer than the bolts they match . Failure occurs because the threads of a new nut become slightly (but permanently) compressed when tightened the first time. This is referred to as the nut being "plastically" deformed. The second time the nut is used, the threads grip the bolt a little "tighter" using more of the applied torque to overcome thread friction and less of the torque to clamping force . Each time the nut is reused it loses more of its clamping power . The result is the same as an undertightened assembly even though a service technician were to follow a torque chart and use a torque wrench . In some cases, nuts that have been reused as few as five times have been shown to be capable of only 57 percent of their original clamping force . Such a loss of pre-load would not only allow parts to shift out of alignment, it could also encourage fatigue failure . HEAT-TREATED BOLT - Bolts of Grade 5 and higher are heat treated for greater strength. When these bolts are used in areas of vibration, extra care must be taken to be certain they are properly installed and tightened to avoid fatigue failure . In vibration areas, any condition that prevents a bolt from being properly pre-loaded or that causes the pre-load to deteriorate will activate fatigue failure . Quite often the initial tension is lost due to gasket compression, soft washers, "mushing out," etc . If a heat-treated bolt is installed without being tightened to its design torque (i .e., undertightened), the operational loads placed on the bolt (vibration, shock or impact) will exceed the clamping force applied using a wrench . Any shock or vibrational load above the yield point of the bolt will cause the bolt to stretch and relax like a spring . Pro- TORQUE WRENCH APPLICATION "DO NOT LUBRICATE" should become a common practice when using a torque wrench and standard torque tables . All torque chart values are valid only for clean, dry threads on new nuts and bolts unless otherwise called for in specific shop manual applications. APPENDIX C NUT AND BOLT IDENTIFICATION (Cont'd) The reason for this is that any sort of lubrication cuts thread friction which allows more of the tightening torque to be converted to clamping force than has been accounted for in the torque chart. True DRY threads seldom exist as there are degrees of "oiliness" of different thread lubricants . If oiled threads or anti-sieze compounds are called for in a shop manual application, the manual will also call out a specific torque value for the area discussed . A manual might ask for a 10 percent reduction of torque when engine oil is a lubricant to as high as a 40 percent reduction of torque from the normal torque chart values when an anti-sieze compound is used. Nuts are available in three standard grades as follows : These are square nuts and are used in some basic farm machinery, construction and industrial machines . They are usually quite bulky and do not contain the quality of steel used in automotive nuts. 1 . S .A .E . GRADE 2 - 2. These nuts are made of medium carbon steel and are not marked . They may be plain steel or zinc coated and are used on bolts up through S.A.E . Grade 5 or GM-280M bolts . S .A .E GRADE 5 (GM-286M) - A new torque method is being used in certain shop manual 3. S.A.E . GRADE 8 (GM-301 M) - These nuts are made applications which is called a torque turn technique . Using of medium carbon steel that is heat treated and this method, the bolt is torqued to a very low setting which quenched . They are marked with three (3) dots equally is easy to obtain. Friction of the bolt head and/or dirt in spaced around the top surface of the nut . GM-301 M the threads are of little consequence as this method is nuts are made of special steel and are identified by a essentially a "snugging" process . After "snugged" to the copper flash or yellow chromate finish . Thick nuts such light torque value called for, the shop manual will call for as those used on spring U-bolts are also special nuts an additional 90 degree turn, or some specific number of that should not be substituted . degrees . Using elaborate measuring procedures, GM Engineering has determined that a service technician can, NOTE : S.A.E. GRADE 6 & 7 and GM-290M bolts are arrive at a near ideal amount of bolt stretch for the given production-only parts and not carried by GM bolt size and application and an ideal clamp load of the parts . If a replacement is needed, use Grade 8. workpieces. STANDARDS FOR NUT AND BOLT GRADES The basic standards for nut and bolt grades were established by the Society of Automotive Engineers (S.A.E.). General Motors has a corresponding rating system . There are four basic grades of bolts used in assembly today . They are as follows : -All have unmarked bolt heads and are not heat treated . 1 . S .A .E. GRADE 1, 2, 3, & 4 (GM-260M) 2. 3. 4. S .A .E . GRADE 5 (GM-280M) -All have three (3) lines on the bolt head dividing the head into three equal parts . These bolts are carbon steel with rolled heads, quenched and tempered in oil or water. S.A.E . GRADE 6 & 7 (GM-290M) - All have four (4) or five (5) lines on the bolt head which divide this head into quarters or fifths.: These bolts are medium carbon alloy steel with rolled heads, heat treated, quenched in oil and drawn. All have six (6) marks on the bolt head equally spaced around the top . These bolts are made from carbon alloy steel, heat treated, oil quenched and temper drawn at 800 degrees Fahrenheit . S .A.E . GRADE 8 (GM300M) -- A-9 SERVICE TIPS Some important points to observe are as follows : " Always consult the appropriate shop manual for a given bolt torque as the first torque preference. The following torque charts are helpful for non-listed bolts. USE A TORQUE WRENCH . Hand tightening is simply a guessing game. An impact wrench (rattle gun) is more of a guessing game than hand tightening . " Never replace a bolt with one of a lesser grade than the original . " Do not exceed the nut or bolt torque listed on the charts for the grade and size bolt being used. Use lubricant on the bolt threads and/or head bearing surface ONLY when called for in the service manual . " Avoid using an impact wrench (rattle gun) to apply torque values to any nut or bolt. (NOTE: Some factory assembly line rattle guns can be used as they are generally used in a specific application and torque accuracy is checked each shift.) If an impact wrench is used on torque prevailing nuts and bolts (nylon washer, strip or patch), . it is recommended that the fasteners be replaced, due to the abuse of the impact gun . APPENDIX C NUT AND BOLT IDENTIFICATION (Cont'd) Common metric fastener strength property classes are 9 .8 and 10.9 with the class identification embossed on the head of each bolt . Customary (inch) strength classes range from grade 2 to 8 with line identification embossed on each bolt head. Markings correspond to two lines less than the actual grade (i.e. grade 7 bolt will exhibit 5 embossed lines on the bolt head). Some metric nuts will be marked with single-digit strength identification numbers on the nut face. The following figure illustrates the different strength markings. NUT AND BOLT IDENTIFICATION GRADE 2 (GM 260-M) GRADE 5 (GM 280-M) GRADE 7 (GM 290-M) GRADE 8 (GM 300-M) Customary (inch) bolts - Identification marks correspond to bolt strength- Increasing numbers represent increasing strength. Metric Bolts - Identification class numbers correspond to bolt strength - Increasing numbers represent increasing strength. MANUFACTURERS IDENTIFICATION NUT STRENGTH IDENTIFICATION POSIDRIV SCREW HEAD IDENTIFICATION MARKS (4) APPENDIX C NUT AND BOLT IDENTIFICATION (Cont'd) STANDARD CAPSCREW MARKINGS AND TORQUE Current Usage Minimum Tensile Strength PSI MPa Quality of Material SAE Grade Number Much Used Much Used To 1/2-69,000 [476] To 3/4-64,000 [421] To 1-55,000 13791 To 3/4-120,000 [827] To 1-115,000 [793] To 5/8-140,000 [965] To 3/4-133,000 [917] Minimum Commercial Medium Commercial Indeterminate 1 or 2 Capscrew Head Markings Manufacturer's r marks may vary are all SAE Grade 5 (3 lines) Y Capscrew Body Size (Inches) (Thread) 1/4 -20 -28 5/16-18 -24 3/8 -16 -24 7/16-14 -20 1/2 -13 -20 9/16-12 -18 5/8 - 11 -18 3/4 -10 -16 7/8 - 9 -14 1 - 8 -14 Torque Ft.-Lb. [N"m] 5 6 11 13 18 20 28 30 39 41 51 55 83 95 105 115 160 175 235 250 [7] [8] [15] [18] [24] [271 [38] [411 [53] [56] [69] [75] [113] [129] [1421 [156] [2171 [237] [319] [339] 5 Used at Times Used at Times 150,000 [1,034] Best Commercial 6 or 7 8 6 '= .- (GM280) 7 (GM290) (GM300) Torque Ft.-Lb. [N"m] Torque Ft.-Lb. [N"m] Torque Ft.-Lb. [N"m] 8 [ill 10 [14] 17 [231 19 [26] 31 [42] 35 [47] 49 [66] 55 [751 75 [102] 85 [1151 110 [149] 120(1631 150 [203] 170 [231] 270 [366] 295 [400] 395 [5361 435 [590] 590(8001 660 [895] 10 [141 19 [26] 34 [46] 55 [75] 85 [115] 120 [163] 167 [226] 280 [380] 440 [5971 660 [8951 12 14 24 27 44 49 70 78 105 120 155 170 210 240 375 420 605 675 910 990 [161 [191 [331 [37] [60] [66] [95] [1061 [142] [1631 [210] [231] [285] [325] [5081 [569] [8201 [915] [12341 [1342] 1 . Always use the torque values listed above when definite specifications are not available . Note: Do not use standard values in place of those specified for the above engine groups. Special attention should be observed in case of SAE Grade 6, 7 and 8 capscrews . Refer to applicable Shop Manual . 2. The above is based on use of clean and dry threads . 3. Reduce torque by 10% when engine oil is used as a lubricant . 4. Reduce torque to 20% if new plated capscrews are used. CAUTION : CAPSCREWS THREADED INTO ALUMINUM MAY REQUIRE REDUCTIONS IN TORQUE OF 30% OR MORE, UNLESS INSERTS ARE USED. 1 APPENDIX C NUT AND BOLT IDENTIFICATION (Cont'd) METRIC TORQUE CHART- NEWTON-METERS ** Metric Bolt Grade Bolt Diame Metric Inch - ' Torque Newton-meter M5 .197 3 .2 4.4 5.5 7 .2 M6 .236 5.5 7.7 8.8 12.1 M7 .276 8.8 12.1 1 5.4 M8 .315 13.2 17.6. M10 .394 25.3 M12 .472 M14 8.8 . 12.1 13 .2 15.4 19.8 23.1 21 .9 26.4 30.3 38.5 22 .0 29.7 37.4 48.4 55.0 35.2 40 .4 60.5 77.0 93.5 110 .0 44 .0 61 .6 77.0 104.5 132.0 165 .0 198 .0 .551 7 1 .5 99.0 121 .0 132.0 209 .0 264 .0 308 .0 M16 .630 110.0 154.0 187 .0 297 .0 319 .0 418 .0 484 .0 M20 .787 220 .0 291 .5 363 .0 572 .0 693.0 814 .0 946 .0 M24 .945 374 .0 506 .0 638.0 1012.0 1199 .0 1386.0 1628.0 M30 1 .181 748.0 1166.0 1440 .0 2002.0 2387.0 2772 .0 3234.0 1 . Always use the torque values listed above when definite specifications are not available . 2. The above is based on use of clean and dry threads . 3. Reduce torque by 10% when engine oil is used as a lubricant. 4. Reduce torque to 20% if new plated capscrews are used . CAUTION : CAPSCREWS THREADED INTO ALUMINUM MAY REQUIRE REDUCTIONS IN TORQUE OF 30% OR MORE, UNLESS INSERTS ARE USED. ** NOTE: Use only when manufacturer's specifications are not available. These values are for stiff metal-to-metal joints and are based on 90% of proof load. Do not use for gasketed joints or joints of soft materials. APPENDIX G NUT AND BOLT IDENTIFICATION (Cont'd) NON-LISTED TORQUE VALUES Pipe Plugs and Fittings Torque Pipe Thread Size In Bosses or Aluminum Ft./Lb. [N-m] In Case Iron or Steel Ft./Lb. [N-m] 1/16 1/8 1/4 3/8 1/2 3/4 1 1-1/4 1-1/2 3.3-3.7 [4.5-5.0] 5-10 [7-14] 10-15 [14-20] 15-20 [20-27] 20-25 [27-34] 30-35 [41-47] 40-45 [54-61] 50-55 [68-75] 60-65 [81-88] 5-10 [7-14] 10-15 [14-20] 15-20 [20-27] 20-25 [27-34] 35-40 [47-54] 50-55 [68-75] 65-70 [88-95] 80-85 [108-115] 95-100 [129-136] Hose Swivel Nut Torque Hose Size Torque Ft./Lb. [N-m] No. No. No. No. No. No. No. No. No. 4.5-5 [6-7] 5-10 [7-14] 15-20 [20-27] 25-30 [34-411 35-40 [47-54] 50-60 [68-81] 65-75 [88-102] 90-100 [122-136] 130-140 [176-190] 4 6 8 10 12 16 20 25 32 Flared (Internal or External) Tube Nut Torque Tube Size Torque Ft./Lb. [N-m] 3/16 1/4 5/16 3/8 1/2 5/8 3/4 7/8 1 7-7 .5 [9-101 10-15 [14-20] 15-20 [20-27] 20-25 [27-34] 25-30 [34-41] 40-45 [54-611 45-50 [61-68] 50-60 [68-81] 60-70 [81 --95] Note: Use these torque values when a specific torque is not listed . Flexible Sleeve Tube Fitting Torque Tube Size Torque Ft./Lb. [N-m] 1/4 inch 1/2 inch 7/8 inch 1-1/4 inch 5-10 [7-14] 10-15 [14-20] 15-20 [20-27] 20-25 [27-34] Hose Clamp Torque Type ., Torque In ./Lb. [N-m] T-Bolt Worm Screw 65-75 [7.3-8.5] 35-45 [3.9-5.1] APPENDIX C NUT AND BOLT IDENTIFICATION (Cont1d) THREAD REPAIR INFORMATION THREADS STRIPPED Occasionally, both internal and external threads may become only partially stripped . In such cases, they can often be repaired or cleaned up through the use of a thread die or tap . DRILLED AND TAPPED OVERSIZE When threads in holes are damaged beyond repair, there are generally three choices of corrective actions. They are : 1 . The hole may be drilled and tapped to the next suitable oversize and a larger diameter cap screw or stud installed . Use a chart to determine the proper tap size to use . A clearance or body drill (a drill that is the size of the bolt's major diameter) must be passed through the attaching part to allow an oversize cap screw to be used. REPAIR STRIPPED THREADS BY DRILLING AND TAPPING TO NEXT OVERSIZE m SECA CAP SCREW 11111111 2. The hole may be drilled and tapped to accept a threaded plug. The plug is drilled and tapped to the original screw size. A self-tapping plug that is already threaded to the original size may be used. For this repair, you must drill a hole to the specified size, run a threaded plug into the hole by using a cap screw and jam nut . When fully seated, the jam nut is loosened and the cap screw and jam nut are removed . LOCK OR JAM NUT THREADED PLUG DRILLED AND /TAPPED INSERT THREADED PLUG TO REPAIR STRIPPED THREADS STANDARD SCREW FITS INTO HELI-COILS INSERT 3. The hole may be drilled and tapped to accept a patented coil wire insert called a Heli-Coil® . A special tap is used that accomodates the odd size of the Heli-Coil©. The Heli-Coil® is then inserted using a special tool. This procedure brings the hole back to its original diameter and thread specifications . Heli-Coils© are available in standard threads as well as metric threads . HELI-COIL® FITS TAPPED HOLE REPAIR STRIPPED THREADS USING A HELI-COIL° A- 1 4 APPENDIX D WEIGHT DISTRIBUTION AND HELPFUL CONVERSIONS Weight distribution of any special equipment item can be determined if the centerline (CL) or the center of gravity point is known in relation to the centerline of the axle . Once this dimension is known, divide this dimension by the wheelbase dimension. Substituting the correct figures in the formula shown above would result in the following : 102 - 3 - 84 _ 15 = 8 . 98 or 9% 167 167 The same rule applies if the centerline or center of gravity point is outside the wheelbase (such as a liftgate, snowplow or front-mounted winch) . 9% front, '91% rear Determine the distance from the closest axle and divide by the wheelbase . When the center of gravity point is outside the wheelbase, it results in negative weight distribution . In other words, the total amount of weight outside the axle is added to the closest axle plus the amount of weight that is taken off the opposite axle . As an example, the body-payload weight distribution might be 9/91 percent for a 14-foot body with a 167-inch WB (wheelbase) - 102-inch CA (cab-to-axle) . The 15" listed above means that the centerline (CL) of the body is 15" forward of the centerline (CL) of the rear axle. Examples of weight distribution showing various factors appear on the chart below. WEIGHT DISTRIBUTION FACTORS WEIGHT DISTRIBUTION LOAD CENTER DIRECTLY IN MIDDLE OF WHEELBASE. 50% FRONT AXLE 50% REAR AXLE 50% 50% LOAD CENTER DIRECTLY OVER CENTERLINE OF FRONT AXLE . 100% FRONT AXLE 0% REAR AXLE 100% 0 O "41# T 32" LOAD CENTER DIRECTLY OVER CENTERLINE OF REAR AXLE . 0% - 0% FRONT AXLE 100% REAR AXLE 100% FRONT MOUNTED WINCH 500 POUNDS 630 LBS . 125" WB 0 LOAD CENTER OF WINCH 32" BEYOND FRONTAXLE CENTERLINE . 32" DIVIDED BY 125"WB = 26° 126% OF WINCH WEIGHT ON FRONT COMPONENTS . REAR COMPONENTS LIGHTENED BY 26%. -130 LBS. LOAD CENTER OF DEAD-WEIGHT . HITCH LOAD 50" BEHIND REAR AXLE CENTERLINE . 50" DIVIDED BY 125"WB = 40% .140% OF HITCH LOAD ON REAR COMPONENTS . FRONT COMPONENTS LIGHTENED BY 40%. A- 1 5 APPENDIX D WEIGHT DISTRIBUTION AND HELPFUL CONVERSIONS (Cont'd) HELPFUL CONVERSIONS AND CONSTANTS MULTIPLY BY TO OBTAIN Gallons 231 .0 Cubic Inches Gallons 3.7854 Cubic Feet Cubic Feet Liters 1728.0 Cubic Inches 7.480 Gallons 1 Cubic Foot = 7.4805 Gallons 1 Cubic Foot = 1728 Cubic Inches Pi = 3 .14.16 To Determine VOLUME OF A CYLINDER = Pi times radius squared times length or height . Most RV hot water tanks are 6 gallons, figure 50 to 55 pounds to include water in the plumbing . Propane tanks are never filled more than 80% by law to allow 20% expansion chamber for temperature changes . 4 To Determine VOLUME OF A BOX = Length times height times depth. To Determine WEIGHT DISTRIBUTION INSIDE WHEELBASE _ Number of inches behind front wheel divided by wheelbase . Example : 36" divided by 178" wheelbase equals 20% weight added to rear wheels, 80% to, front axle. WEIGHT DISTRIBUTION OUTSIDE WHEELBASE = Determine the distance from the closest axle and divide by the wheelbase . Example : a hitch 144" behind the axle divided by wheelbase of 178" equals 80% or 180% of hitch load on rear axle, the excess over 100% being removed from the front axle. Typical Weights Water 8.328 7.0 Diesel fuel Gasoline fuel 6.0 .23 Propane C3 H8 pounds pounds pounds pounds per per per per gallon gallon gallon gallon APPENDIX D WEIGHT DISTRIBUTION AND HELPFUL CONVERSIONS (Cont'd) METRIC - ENGLISH CONVERSION TABLE MULTIPLY TO GET EQUIVALENT NUMBER OF: BY LENGTH 25.4 0.3048 0,9144 1 .609 Inch Foot Yard Mile AREA 645 .2 6.45 0.0929 0.8361 Inch2 Foot2 Yard2 Quart Gallon Yard3 VOLUME 16387. 16.387 0.0164 0.9464 3.7854 0 .7646 Pound Ton Ton MASS 0 .4536 907 .18 0.907 Kilogram Ounce Pound FORCE 9.807 0.2780 4.448 Inch3 Degree Fahrenheit (F) T -40 0 -40 -20 'C MULTIPLY BY millimeters (mm) meters (m) meters (m) kilometers (km) Foot/sect Inch/sect ACCELERATION 0 .3048 0.0254 millimeters 2 (mm 2) centimeters2 (cm2) meters2 (m2) meters2 (m2) Foot pound 40 0 80 20 98.6 37 40 Horsepower mm3 cm3 liters (I) liters (I) liters (I) meters3 (m3) . kilograms (kg) kilograms (kg) tonne (t) 120 160 60 80 joules (J) joules (J) joules (J =one W's) Gal/mile 212 Miles/hour 100 oC A-1 7 kilowatts (kw) ENERGY OR WORK BTU 1 055 . Foot pound 1 .3558 Kilowatt-hour 3 600 000 . or 3.6 x 106 Miles/gal 200 POWER 0.746 newton-meters (N" m) newton-meters kilopascals (kPa) kilopascals (kPa) newtons (N) newtons (N) newtons (N) °F 1 .3558 meter/sect (m/s2) meter/sect (m/s2) PRESSURE OR STRESS Inches of water 0.2491 Pounds/sq . in. 6.895 Foot candle TEMPERATURE degree - 1 .8 = Celsius (C) -32 3 Inch pound TORQUE 0.11298 TO GET EQUIVALENT NUMBER OF: LIGHT 1 .0764 FUEL PERFORMANCE 0.4251 2.3527 VELOCITY 1 .6093 lumens/meter2 (IM/M2) kilometers/liter (km/1) liters/kilometer (1/km) kilometers/hr . (km/h) APPENDIX D WEIGHT DISTRIBUTION AND HELPFUL CONVERSIONS (Cont'd) DECIMAL EQUIVALENTS 1 1 1 1 1 1 MilliDec. meter Equiv. .1 .0039 .15 .0059 .2 . .0079 .25 .0098 .3 .0118 .0135 .35 .0138 .0145 .39 .0156 .4 .0157 .0160 .45 .0177 .0180 .5 .0197 .0200 .0210 .55 .0217 .0225 .6 .0236 .0240 .0250 .65 .0256 . .0260 .0280 .7 .0286 .0292 .75 .0295 .0310 .79 .0312 .8 .0315 .0320 .0330 .85 .0335 .0350 .9 .0354 .0360 .0370 .95 .0374 .0380 .0390 1 .0 .0394 .0400 .0410 1 .05 .0413 .0420 .0430 1 .1 .0433 1 .15 .0452 .0465 1.19 .0469 1 .2 .0472 1 .25 .0492 1 .3 .0512 .0520 1 .35 .0531 .0550 1 .4 .0551 1 .45 .0570 1 .5 .0591 .0595 1 .55 .0610 1 .59 .0625 1 .6 .0629 .0635 1 .65 .0649 1 .7 .0669 .0670 OF MILLIMETER, FRACTIONAL & NUMBER 1 mm = 0.03937 in. 1 yd . = 0.9144 m 1 cm = 0.3937 in. 1 sq . in. = 6.452 sq . c m 1 dm = 3.937 in. 1 sq . ft. = 929 sq. cm m = 39.37 in. 1 sq . yd. = 0 .8361 sq. m 1 in = 25.4 mm 1 sq . cm = 0.155 sq. in. 1 foot = 0 .3048 m 1 sq. dm = 15 .5 sq. in. 1 Fractional Number 80 1/64 79 78 . 77 76 75 74 73 72 71 70 69 1/32 68 67 66 65 64 63 62 61 60 59 58 57 3/64 56 - 55 54 53 1/16 52 51 Milllmeter Dec . Equiv. 1 .75 1 .8 1 .85 1 .9 1 .95 1 .98 2.0 2.05 2.1 2.15 2.2 2.25 2.3 2.35 2.38 2.4 2.45 2.5 2.6 2.7 2.75 2.78 2 .8 2 .9 3 .0 3 .1 3 .18 3 .2 3 .25 3 .3 3 .4 3 .5 3 .57 3 .6 3 .7 3 .75 3.8 3 .9 3.97 .0689 .0700 .0709 .0728 .0730 .0748 .0760 .0767 .0781 .0785 .0787 .0807 .0810 .0820 .0827 .0846 .0860 .0866 .0885 .0890 .0905 .0925 .0935 .0937 .0945 .0960 .0964 .0980 .0984 .0995 .1015 .1024 .1040 .1063 .1065 .1082 .1094 .1100 .1102 .1110 .1130 .1141 .1160 .1181 .1200 .1220 .1250 .1260 .1279 .1285 .1299 .1338 .1360 .1378 .1405 .1406 .1417 .1440 .1457 .1470 .1476 .1495 .1496 .1520 .1535 ,1540 .1562 Fractional Numbar 50 49 48 5/64 47 46 45 44 43 3/32 42 41 40 39 38 37 36 7/64 35 34 33 32 31 1/9 30 29 9/64 28 27 26 25 24 5/32 23 - Milli . meter Dec. Equiv . 4 .0 4.1 4 .2 4.25 4.3 4.37 4.4 4.5 4.6 4.7 4.75 4.76 4.8 4.9 -, 5.0 5.1 5.16 5.2 5.25 5.3 5.4 5.5 5.56 5.6 5.7 5.75 5 .8 5 .9 5 .95 6 .0 6 .1 6 .2 6 .25 6 .3 6 .35 6 .4, 6 .5 6.6 6 .7 6 .75 6.75 - .1570 .1575 .1590 .1610 .1614 .1654 .1660 .1673 .1693 .1695 .1719 .1730 .1732 .1770 .1771 .1800 .1811 .1820 .1850 .1870 .1875 .1890 .1910 .1929 .1935 .1960 .1968 .1990 .2008 .2010 .2031 .2040 .2047 .2055 .2067 .2086 .2090 .2126 .2130 .2165 .2187 .2205 .2210 .2244 .2263 .2280 .2283 .2323 .2340 .2344 .2362 .2380 .2401 .2420 .2441 .2460 .2480 .2500 .2520 .2559 .2570 .2598 ".2610 .2638 .2656 .2657 .2660 A- 1 8 Fractional Numbar Milllmotor Dec. Equiv. 22 6.8 6.9 7.0 7.1 7.14 7.2 7.25 7.3 7.4 7.5 7.54 7.6 7.7 7.75 7.8 7.9 7.94 8.0 8.1 6.2 8.25 8.3 8 .33 8 .4 8 .5 8 .6 8 .7 8 .73 8 .75 8 .8 8 .9 9 .0 9 .1 9.13 9.2 9 .25 9 .3 9.4 9.5 9.53 9.6 9.7 9.75 9.8 9.9 9.92 10.0 10.32 10.5 .2677 .2716 .2720 .2756 .2770 .2795 .2811 .2812 .2835 .2854 .2874 .2900 .2913 .2950 .2953 .2968 .2992 .3020 .3031 .3051 .3071 .3110 .3125 .3150 .3160 .3189 .3226 .3230 .3248 .3268 .3281 .3307 .3320 .3346 .3386 .3390 .3425 .3437 .3445 .3465 .3480 .3504 .3543 .3580 .3583 .3594 .3622 .3641 .3661 .3680 .3701 .3740 .3750 .3770 .3780 .3819 .3838 .3858 .3860 .3898 .3906 .3937 .3970 .4040 .4062 .4130 .4134 21 20 19 11/64 18 17 16 15 14 13 3/16 12 11 10 9 8. 13/64 7 6 5 4 3 7/32 2 1 15/64 A B C D 1/4 E F G 17/64 DRILL SIZES sq. m = 1 .196 sq. yd . oz . = 31 .1035 grams lb . = 373 .24 grams qt. = 0 .9463 liters (liquid) gal . = 3.7853 liters (liquid) liter = 1 .0567 liquid qt. H - Fractional Numbar 1 1 9/32 K - L M 19/64 N 5/16 0 P 21/64 O R 11132 S T 23/64 - U 3/8 - v W 25/64 13/32 X Y Z Millimeter Dec. Equiv. Fractional 10 .72 11 .0 11 .11 11 .5 11 .51 11 .91 12.0 12 .30 12 .5 12 .7 13 .0 13 .10 13 .49 13 .5 13 .89 14 .0 14 .29 14 .5 14 .68 15 .0 15 .08 15 .48 15.5 15 .88 16 .0 16 .27 16.5 16.67 17.0 17.06 17.46 17.5 17.86 18.0 18.26 18.5 18.65 19.0 19.05 19.45 19.5 19.84 20 .0 20.24 20.5 20.64 21 .0 21 .03 21 .43 21 .5 21 .83 22 .0 22 .23 22 .5 22 .62 23 .0 23 .02 23.42 23.5 23 .81 24 .0 24.21 24 .5 24 .61 25 .0 25.03 25.4 .4219 .4330 .4375 .4528 .4531 .4687 .4724 .4843 .4921 .5000 .5118 .5156 .5312 .5315 .5469 .5512 .5625 .5709 .5781 .5906 .5937 .6094 .6102 .6250 .6299 .6406 .6496 .6562 .6693 .6719 .6875 .6890 .7031 .7087 .7187 .7283 .7344 .7480 .7500 .7656 .7677 .7812 .7874 .7969 .8071 .8125 .8268 .8281 .8437 .8465 .8594 .8661 .8750 .8858 .8906 .9055 .9062 .9219 .9252 .9375 .9449 .9531 .9646 .9687 .9843 .9844 1 .0000 27/64 7/16 29/64 15/32 31/64 112 33/64 17/32 35/64 9/16 37/64 19/32 39/64 5/8 41/64 21/32 43/64 11/16 45/64 23/32 47/64 3/4 49/64 25/32 51/64 13/16 53/64 27/32 55/64 7/8 57/64 29/32 59/64 15/16 61/64 31/32 63/64 1 APPENDIX D WEIGHT DISTRIBUTION AND HELPFUL CONVERSIONS (Cont'd) TORQUE CONVERSION TABLE NEWTON-METERS [N"m] FOOT-POUNDS .-LTA ( .) FOOT POUNDS .-LTA ( .) NEWTON-METERS [N"m] 1 2 3 4 5 6 7 8 9 10 15 20 25 30 35 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200 225 250 0.7376 1 .5 2.2 3 .0 3.7 4.4 5.2 5.9 6.6 7.4 11.1 14.8 18.4 22 .1 25.8 29.5 36.9 44.3 51.6 59.0 66.4 73.8 81.1 88.5 95.9 103 .3 110 .6 118.0 125 .4 132 .8 140 .1 147.5 166 .0 184 .4 1 2 3 4 5 6 7 8 9 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 90 100 110 120 130 140 150 160 170 180 1 .356 2 .7 4.0 5.4 6.8 8.1 9.5 10.8 12 .2 13.6 20.3 27.1 33.9 40.7 47.5 54.2 61 .0 67.8 74.6 81 .4 88.1 94.9 101.7 108 .5 122 .0 135 .6 149 .1 162 .7 176 .3 189 .8 203 .4 216 .9 230 .5 244 .0 INDEX A Accumulator - AC . . . . . . . . . . . . . . . . . . . . . 2-2 Additives - Fuel . . . . . . . . . . . . . . . . . . .. . . . 7-22 Additives - Radiator (Appendix 7-2) . . . . . . . 7-20 Add-On Electrical Equipment (Appendix 7-11) . . . . . . . . . . . . . . . . . . . . . . . . 7-79 Aftermarket Fuel Systems (Appendix 7-8) . . . 7-50 Aftermarket Suspension Devices . . . . . . . . . 3-10 Air Bag Cylinder Inspection . . . . . . . . . . . . . . . 3-9 Air Bag Replacement . . . . . . . . . . . . . . . . . . . . 3-9 Air Cleaner - Polywrap . . . . . . . . . . . . . . . . 7-100 Air Cleaner Element Replacement . . . . . . . . 7-99 Air Conditioning Belt (Appendix A) . . . . . . . . . A-4 Air Conditioning System . . . . . . . . . . . . . . . . . 2-2 Air Conditioning System Optional (Appendix 2-1) . . . . . . . . . . . . . . . . . . 2-6 Air Distribution Section - A/C . . . . . . . . . . . . 2-5 Air Flow - Engine Compartment . . . . . . . . . . 7-4 Air Pump Drive Belt . . . . . . . . . . . . . . . . . . . . 7-99 A.I.R. Connector Diagram (Appendix 7-17) . 7-101 A.I.R. Connector Module (Appendix 7-17) . . 7-102 A.I.R. Filter Canister (Appendix 7-17) . . . . . . 7-105 Air Injection Reactor System Gasoline Engine . . . . . . . . . . . . . . . . . . . . . . . . 7-97 A.I.R. Pump Belt (Appendix A) . . . . . . . . . . . . . A-4 Alignment - Front Suspension . . . . . . . . . 3-1, 3-2 Automatic Transmission - 350C and ' 400-475 Series . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1 Automatic Transmission 4L8DE ...... . . . . . . . . . . . . . ... .. .8-7 Automatic Transmission Fluid . . . .. ...... . . . . . . . . . . . . . ....8-9 Automatic Transmission Manual Linkage 8-2, 8-5 Auxiliary Electrical Equipment (Appendix 7-11) . . . . . . . . . . . . . . . . . . . 7-79 Auxiliary Fuel Tank Considerations . . . . 7-29,7-30 . . . . Average Life of Gears . . . . . . . . . . . . . . . .. .. .. .. .. 5-3 Axle Housing . . . . . . . . . . . . . . . . . . . . . 5-3 B Ball Joint Inspection . . . . . . . . . . . . . . . . . . . . 3-3 Battery . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 7-55 Battery Isolator . . . . . . . . . . . . . . . . . . . . . . . . 7-62 Battery Maintenance During Vehicle Storage (Appendix B) . . . . . . . . . . . . . . . . . . . . . . . . . . . A-6 Battery Ratings . . . . . . . . . . . 7-55 Battery Removal and Replacement . . . . . . . . . . . . . 7-59 Battery Size and Cranking (Appendix 7-10) . . 7-75 Belt Installation/Replacement (Appendix A) . . A-2 Belt Specifications (Appendix A) . . . . . . . . A-3, A-4 Belt Wear (Appendix A) . . . . . . . . . . . . . . .. . A-1 Bent Axle Housing . . . . . . . . . . . . . . . . . . .. .. . 5-3 Bent Rim Check . . . . . . . . . . . . . . . . . . . . . . . 3-17 Bleeding Brakes . . . . . . . . . . . . . . . . . . . . . 6-7,6-8 Bolt Identification (Appendix C) . . . . . . . . . . . A-7 B (Cont'd) Boot Puller - Spark Plug . . . .. ... . . . . . . . . . . . .. ...... . . . . .7-71 Brake Bleeder - Vacuum (Appendix 6-2) .... . . .6-13 Brake Caliper Noise (Appendix 6-1) . . . . . . . . . . ...... . . .6-6 Brake Drum . . . . . . . . . . . . . . . . . . . . . . . . 6-3,6-5 Brake Hose Inspection . . . . . . . . . . . . . . . . . . . 6-5 Brake Lining . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-5 Brake Lining Life Expectancy (Appendix 6-3) . . . . . . . . . . . . . . . . . . . . . . . . . 6-14 Brake Master Cylinder . . . . . . . . . . . . . . . . . . . 6-5 Brake Pedal/Stoplight Adjustment . . . . . . . . . 6-6 Brake Rotor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6 Brakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1 Built-in Hydrometer - Battery . . . . . . . . . . . 7-56 C Caliper - Brake . . . . . . . . . . . ........ . . . . . . . . . . . .. ... . . . . . . . . . . . .. . 6-6 Camber .. .. . . . . . . . . . . . . . . .. .. ........ . . . . . . . . . .. ... .. . . . . . . . . . . . .....3-1 Canister Purge Control Valve . . . . . . . . . . . . . 7-96 Capscrew Markings (Appendix C) . . . . . . . . . A-11 Carburetor . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-31 Caster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 Cast Iron Manifold . . . . . . . . . . . . . . . . . . . . . . 7-3 Center Bearing . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 Certification Label . . . . . . . . . . . . . . . . . . . . . 3-13 Changing Transmission Fluid . . . . . . . . . . . . . 8-4 Charging System . . . . 7-62,7-64 Chassis . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 Check Valve Inspection . . . . . . . . . . . . . . . . . . . . 7-99 Cold Advance Solenoid . . . : . . . . . . . . . . 7-72 Cold Start Circuit - Diesel Engine . . . . . . . . . . . 7-73 Compressor Assembly (Appendix 2-1) . . . . . . . 2-6 Condenser Assembly (Appendix 2-1) . . . . . . . . 2-7 Condenser Kit With Oil Cooler (Appendix 2-1) . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9 Condenser Kit Without Oil Cooler . . . . . . . . . . 2-8 (Appendix 2-1) Condenser With. . Fans . . . . . Wiring . . . . . . Diagram . . . (Appendix 2-1) . . . . . . . . . . . . . . . . . . . . . . . . . 2-11 Conversions and Constants (Appendix D) . . A-16 Coolant Level . . . . . . . . . . . . . . . . . . . . . . . . . 7-17 Cooler Lines Automatic Transmission . . . . . . . . . . . . . . . . . 8-5 Cooling Fans . . . . . . . . . . . . . . . . . . . . . . . . . 7-14 Cooling Instructions To RV Manufacturers (Appendix 7-3) . . . . . . . . . . . . . . . . . . . . . . . . . 7-21 Cooling System . . . . . . . . . . . . . . . . . . . 7-13,7-19 Cracked Wheel Stud Holes . . . . . . . . . . . . . . 3-16 Crankcase Ventilation - Diesel Engine . . . . 7-93 Cranking System . . . . . . . . . . . . . . . . . . . . . . 7-51 Cruise Control - Electronic (Appendix 7-16) 7-86 CS Series Generator . . . . . . . . . . . . . . . . . . . . 7-65 D Deaeration Cooling System (Appendix 8-1) . . . 8-8 - INDEX (Cont'd) D (Cont'd) .Decimal Equivalents (Appendix D) . . . . . . . . A-18 Detent Downshift Electrical Circuit - 400-475 Series Transmission . . . . . . . . . . . . 8-2 Determining Wheel/Tire Loads . . . . . . . . . . . 3-13 Diesel Engine . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 Diesel Engine Fuel System . . . . . . . . . . . . . . 7-36 Diesel Glow Plug Electrical System . . . . . . . 7-71 Differential Fluid . . . . . . . . . . . . . . . . . . . . . . . 5-1 Differential Housing/Fill Hole . . . . . . . . . . . . . 5-1 Dipstick Replacement . . . . . . . . . . . . . . . . . . 7-10 Disc Brakes . . . . . . . . . . . . . . . . . . . . . . . . 6-296-6 Distributor - H .E.I . . . . . . . . . . . . . 7-66, 7-69,7 .70 Downshift (Detent) Cable 350C Transmission . . . . . . . . . . . . . . . . . . . . . . 8-2 Drive Belt Tension (Appendix A) . . . . . . . . .A-1 Driveline Balance Procedure . . . . . . . 4-3, ..4-4, . . . 4-5 Driveline Noise . . . . . . . . . . . . . . . . . 4-3 Driveline Vibrations - 1 and 2 Drive . . Shaft .. . Systems (Appendix 4-1) . . . . . . . . . . . . . . . . . . 4-6 Driveline Vibrations - 3 Shaft Systems (Appendix 4-2) . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8 Drum Brakes . . . . . . . . . . . . . . . . . . . . . . . 6-3, 6-5 E (Cont'd) Exhaust Manifolds . . . . . . . . . . . . . . . 7-3, 7-4, 7-5 External Fluid Cooler (Appendix 8-1) . . . . . . . . 8-8 F Fan Belt Application Chart (Appendix A) . . . . A-4 Fluids . . . . . . . .. . 1-4,8-7 Flushing Cooling . . System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-19 Frame Angle Measurement . . . . . . . . . . . . . . . 3-3 Front Alignment . . . . . . . . . . . . . . . . . . . . . . . . 3-1 Front Coil Spring Replacement . . . . . . . . . . . . 3-9 Front Suspension . . . . . . . . . . . . . . . . . . . . . . . . 3-8 Fuel Control Operation . . . . . . . . . . . . . . . . . 7-32 Fuel Filters . . . . . . . . . . . . . . 7-30, 7-35, 7-37, 7-38 Fuel Pump . . . . . . . . . . . . . . . . . . . . . 7-29,7-35 Fuel Pump - Electric . . (Appendix 7-6) . . . . . . . . . . . . . . . . . . . . . 7-40,7-44 Fuel Properties (Appendix 7-7) . . . . . . . . . . . 7-40 Fuel Return Line Plugged-(Appendix 7-6) . . . . 7-39 Fuel Solenoid . . . . . . . . . . . . . . . . . . . . . . . . . 7-72 Fuel System Plumbing (Appendix 7-7) . . . . . . 7-40 Fuel Systems - Diesel Engines . . . . . . . . . . 7-36 Fuel Systems - Gasoline Engines . . . . . . . . 7-29 Fuel Tank . . . . . . E . . . . . . . . . . . . 7-29,7-36 Fuel Types - Diesel . . . . Engines . . . . . . . . . . . . . . 7-23 Early Fuel Evaporation Fuel Types (ECM) System . . . . . . . . . . . . .. . . . . . . . . . . . . . . . 7-31 Gasoline Engines . . . . . . . . . . . . . 7-22, 7-24, 7-25 (EFE) System . . . . . . . . . . . . . 7-93, 7-97, . 7-98 Fuel Vapor Canister - Auxiliary . . . . . . 7-96 Electrical Circuit Diagnosis - A/C . . . . . . . . 2-5 Fuel Vapor Canister - Primary . . . . . 7-95 Electrical Equipment - Add-On Fuel Vapor Canister Purge Control . . Valve . . . . . . . . 7-96 (Appendix 7-11 . . . . . . . . . . . . . . . . . . . . . . . . 7-79 Fuel Vapor Vent Control Valve . . . . . . . . . . . . 7-96 Electrical Load Test - Battery . . . . . . . . . . . 7-57 Electric Fuel Pump (Appendix 7-7) . . . . . . . . . . . . . . . . . 7-40,742, 7-45 Gasohol . . . . . . . . . . . . . . . . . . . . . 7-22, 7-24, 7-25 Electric Fuel Pump Relay Location (Appendix 7-16) . . . . . . . . . . . . . . . . . . 7-102,7-104 Gasoline Blends (Appendix 7-5) . . . . . . . . . . . 7-25 Electronic Cruise Control (Appendix 7-16) . . . . 7-86 Gasoline Engine . . . . . . . . . . . . . . . . . . . . . . . . 7-2 Energy Conserving Oils . . . . . . . . . . . . . . . . . 7-8 Gear Ratios (Appendix 8-4) . . . . . . . . . . . . . . . 8-12 Engine Cooling Fans . . . . . . . . . . . . . . . . . . . 7-14 Geared Road Speed Determination (Appendix 8-3) . . . . . . . . . . . . . . . . . . . . . . . . . 8-11 Engine Cooling Instructions to RV Manufacturers (Appendix 7-3) . . . . . . . . . 7-21 Generator Belt (Appendix A) . . . . . . . . . . . . . . A-4 Engine Cooling System . . . . . . . . . . . . . . . . . 7-13 Generator Belt Usage - 6.2L Diesel 7-84 Engine Deaeration System . . . . . . . . . . . . . 7-16 (Appendix 7-14) . . . . . . . . Generator Sizing and Selection . . . . . . . . . 7-62 . . . . . . . Engine Electrical System . . . . . . . . . . . . . . . . 7-55 Glow Plug Lamp 7-72 . . . . . . . . . . . . . . . . . . . . . . . Engine Emission Controls . . . . . . . . . . . . . . . 7-92 Engine Fuel Systems . . . . . . . . . . . . . . . . . . . .7-29 Glow Plug Relay . . . . . . . . . . . . . . . . . . . . . . . 7-72 Engine Lubrication . . . . . . . . . . . . . . . . . . . . . 7-6 Glow Plug System - 6.2L Engine . . . . . 7-63,7-72 Engine Oil Consumption (Appendix 7-1) . . . . 7-11 Glow Plug Test . . . . . . . . . . . . . . . . . . . . . . . . . 7-74 Engine Oil Hose Kit (Appendix 2-1) . . . . . . 2-10 G-Series Motor Home Chassis . . . . . . . . . . . . 1-1 Engine Ratings and Specifications - Diesel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 H Engine Ratings and Specifications Hard Steering - Engine Idle . . . . . . . . . . . . . . 3-6 Gasoline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-2 Heating System . . . . . . . . . . . . . . . . . . . . . . . . 2-1 Evaporative Control System . . . . . . . . . . . . . 7-29 H.E.I . Distributor . . . . . . . . . . . . . . 7-66, 7-69, 7-70 Evaporative Emission Control System H .E.I . Magnetic Pick-Up Assembly . . . . . . . . 7-68 (EECS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-94 Heli-Coil(& Thread Repair (Appendix C) . . . . A-14 INDEX (Cont1d) H (Cont'd) Helpful Conversions and Constants (Appendix D) . . . . . . . . . . . . . . . . . . . . . . . . . . A-16 High Ambient Temperatures Starting Problem . . . . . . . . . . . . . . . . . 7-61 "Hot Start" Problem Conditions . .... (Appendix 7-12) . . . . . . . . . . . . . . . . . . . . . . . . 7-80 Hydraulic Brake System . . . . . . . . . . . . . . 6-1,6-7 Hydro-Boost Brake System . . . . . . . . . . . .. 6-3,6-8 H5D Emission System (Appendix 7-16) . . . 7-101 H5D Override Relay (Appendix 7-16) . . . . . . 7-103 Identification Numbers . . . . . . . . . . . . . . 1-1 Idle Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-34 Ignition System . . . . . . . . . . . 7-66 Ignition Timing . . . . . . . . . . . . .. . . . ;. . . . . . . . 7-69 Increased Engine Life (Principles) . . . . . . . . . . . 7-1 Inflation Pressure -Tires . . . . . . . . . . . 3-14,3-15 Injectors TBI . . . . . . . . . . . . . . . . . . . . . . . . . . 7-33 Isolator - Battery . . . . . . . . . . . . . . . . . . . . . 7-62 Isolator Diagnosis . . . . . . . . . . . . . . . . . . . . . 7-65 J Journal Cross . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 Jump Starting Aid . . . . . . . . . . . . . . . . . . . . . . 7-58 Jump Starting With Auxiliary Battery . . . . . . 7-57 N (Cont'd) Nut and Bolt Standards/Grades (Appendix C) . . . . . . . . . . . . . . . . . . . . . . A-9, A-10 0 Oil Change . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9 Oil Consumption (Appendix 7-1) . . . . . . . . . . 7-11 Oil Fill Capacity - 454 Engine . . . . . . . . . . . . 7-9 Oil Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9 Oil Hose Kit (Appendix 2-1) . . . . . . . . . . . . . . . 2-10 Oil Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-9 Oil Pressure Switch Relay (Appendix 7-7) . . . . . . . . . . . . . . . . . . . . . 7-42,7-44 Oil Quality . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . 7-7 Oil Temperature . . . . . . . . . . . . . . . . . . . . . . . . 7-8 Oil Viscosity . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Optional A/C System (Appendix 2-1) . . . . . . . . 2-6 Overheating Tires . . . . . .. . . . . . . . . . . . . . . . . 3-18 Overinflation - Tire Wear . . . . . . . . . . . . . . . 3-18 Overloaded Gears . . . . . . . . . . . . . . . . . . . . . . . 5-3 Overloading Tires . . . . . . . . . . . . . . . . . . . . . . 3-18 Parking Brake . . . . . . . . .. ........ .. . . . . . . . . . .. ... . . . . . . . . . . . 6-4, 6-8 Parking Brake Cable Adjustment . . . . . . . . . . .. ...... . . . . .6-9 Parking Brake Drum Balance .. ... . . . . . . . . . .. .. ...... . . . . .6-9 PCV Filter Replacement . . . . . . . . . . . . . . . . . 7-97 L PCV System - Gasoline Engine . . . . . . 7-92,7-97 Lateral Runout Measurement . . . . . . . . . . . . 3-17 Pedal Travel - Brakes . . . . . . . . . . . . . . . . . . . 6-5 Load Height Curves (Appendix 3-2) . . . . 3-21, 3-22 Plugged Fuel Return Line (Appendix 7-6) . . . . 7-39 Lower Ball Joint Inspection . . . . . . . . . . . . . . . 3-3 Polywrap Air Cleaner . . . . . . . . . . . . . . . . . . 7-100 Lubricant Capacities . . . . . . . . . . . . . . . . . . . . 1-5 Ground Poor Starting Problem . . . . . . . . . 7-61 Lubricants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4 Power Brake Unit . . . . . . . . . . . . . . . . . . . . 6-3,6-8 Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . 1-4, 7-6 Power Steering Belt Application Chart Lubrication Points . . . . . . . . . . . . . . . . . . . 1-6,1-7 A) . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4 (Appendix Power Steering Component Replacement . . . 3-7 M Power Steering Leak Check . . . . . . . . . . . . . . . 3-6 Magnetic Switch Mounting (Appendix 7-12) . 7-80 Power Steering Pump Belt Tension Manual Linkage - Transmission . . . . . . . 8-2,8-5 Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7 Master Cylinder . . . . . . . . . . . . . . . . . . . . . . . . . 6-5 Power Steering System . . . . . . . . 3-5 Methanol/Gasoline Blends (Appendix 7-5) . . 7-25 Power Steering Quick Fixes . . . . . . . . . . . . . . . 3-7 Metric-English Conversion Table Preparation for Storage (Appendix. .B). . . . . . . . . A-5 (Appendix D) . . . . . . . . . . . . . . . . . . . . . . . . . . A-17 Pressure Cap - Radiator . . . . . . . . . . . . . . . 7-11 Metric Torque Chart (Appendix C) . . . . . . . . . A-12 Pressure Regulator . . . . . . . . . . . . . . . . . . . . . 7-33 Modifications for Diesel Starting . . . . . . . . . . 7-73 Pressurized Fuel System Components Motor Home Towing . . . . . . . . . . . . . . . . . . . . . 1-3 7-7) . . . . . . . . . . . . . . . . . . . . . . . . . 7-44 Multi-Battery Electronic Jump Starting Aid . 7-58 (Appendix Pressurized Fuel System Diagnosis (Appendix 7-7) . . . . . . . . . . . . . . . . . . . . . 7-48,7-49 N Primary Fuel Filter Water Drain . . . . . . . . . . . 7-37 Needle Bearings . . . . . . . . . . . . . . . . . . . . . . . . 4-24 Principles of Increased Engine Life . . . . . . . . . 7-1 Nodular Iron Manifold . . . . . . . . . . . . . . 7-3 Propeller Shaft . . . . . . . . . . . . . . . . . . . . . . . . . 4-1 Nut and Bolt Failures/Fatigue (Appendix . . . . . C) . . A-8 Propeller Shaft Drum Brake Adjustment . . . . . 6-9 Nut and Bolt Identification (Appendix C) . . . . A-7 P-Series Motor Home Chassis . . . . . . . . . . . . . 1-1 INDEX (Cont'd) R Radial/Lateral Runout Measurement . . . . . . 3-17 Radiator Additives (Appendix 7-2) . . . . . . . . . 7-20 Radiator Heater and Engine Deaeration System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-16 Radiator Hose Application Chart (Appendix A) . . . . . . . . . . . . . . . . . . . . . . . . . . . A-4 Radiator Pressure Cap . . . . . . . . . . . . . . . . . . 7-11 Rear Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1 Rear Axle Lubrication Fill Hole . . . . . . . . . . . . 5-1 Rear Spring Installation . . . . . . . . . . . . . . . . . 3-12 Rear Suspension . . . . . . . . . . . . . . . . . . . . . . 3-12 Receiver-Dehydrator - A/C . . . . . . . . . . . . . . . 2-2 Recommended Fluids and Lubricants . . . . . . 1-4 Refrigeration Section - A/C . . . . . . . . . . . . . . 2-4 Ride Height Measurement . . . . . . . . . . . . . . . . 3-2 Rim Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-17 Rotor - Brake . . . . . . . . . . . . . . . . . . . . . . . . . 6-6 S Secondary Wiring - H.E.I. Distributor . . . . . 7-67 Secondary Fuel Filter . . . . . . . . . . . . . . . 7-38,7-52 Service Parts Identification Label . . . . . . . . . . 1-3 Shock Absorber Diagnosis . . . . . . . . . . 3-10,3-12 Side Fill Gear Case Capacity . . . . . . . . . . . . . . 1-5 Slip Spline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2 Slow Cranking Diagnosis (Appendix 7-10) . . 7-77,7-78 Solenoid Diagnosis. .(Appendix . . . . . . . . .7-10) . . . . . . . 7-77,7-78 Solenoid Electrical Operation . . . . . . . . . . . . 7-61 Solid State Isolator . . . . . . . . . . . . . . . . . . . . . 7-65 Spacer Block . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11 Spark Plug Boot Puller . . . . .. .. .. .. .. . . . . . . . . . 7-71 Spark Plugs . . . . . . . . . . . . . 7-67, 7-68, 7-69 Spark Plug Wires . . . . . . . . . . . . . . . . . . . . . . 7-70 Special Suspension Equipment (Shock Absorber) . . . . . . . . . . . . . . . . . . . . . . 3-10 Specifications - Drive Belts (Appendix A) . . A-1 Stainless Steel Manifold . . . . . . . . . . . . . . . . . 7-3 Starter Motor Relay Connections (Appendix 7-13) . . . . . . . . . . . . . . . . . . . . . . . . 7-83 Starter Motor Engagement (Appendix 7-13) . 7-83 Starting Motor . . . . . . . . . . . . . . . . . . . . . . . . 7-59 Starting Problems . . . . . . . . . . . . . . . . . . . . . 7-61 Steering Damper Check . . . . . . . . . . . . . . . . . .. 3-4 Steering Linkage . . . . . .. 3-4 Steering Linkage Lubrication . . . . . . . . . . . . . . . . . . 3-4 Steering Linkage Support Assemblies . . . . . . 3-4 Steering Relay Parts Identification (Appendix 3-2) . . . . . . . . . . . . . . . . . . . . . . . . . 3-20 Steering System . . . . . . . . . . . . . . . . . . . . . . . . 3-4 Storage of Motor Home (Appendix B) . . . . . . . A-5 Stripped Thread Repair (Appendix C) . . . . . . . A14 Stud Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-16 Suspension Devices - Aftermarket . . . . . . . 3-10 S (Cont'd) Suspension System . . . . . . . . . . . . 3-8 Synthetic Engine Oil . . . . . . . . . . . . . . . . . . . . . 7-8 T TBI Fuel Injection . . . . . . . . . . . . . . . . . . . . . . 7-31 Temperature Monitors (Appendix 8-2) . . . . . . 8-10 Thermostat . . . . . . . . . . . . . . . . . . 7-13, 7-14, 7-19 Thermostatic Air Cleaner (Thermac) . . . 7-93,7-99 Thread Repair Information (Appendix C) . . . A-14 Tie Rod Parts Identification (Appendix 3-1) . . 3-20 Timing - Ignition . . . . . . . . . . . . . . . . . . . . . . 7-69 Tire Balancing . . . . . . . . . . . . . . . . . . . . . . . . . 3-14 Tire Inflation . . . . . . . . . . . . . . . . . . . . . . . . . . 3-18 Tire Inspection and Rotation . . . . . . . . . . . . . 3-13 Tire Overheating . . . . . . . . . . . . . . . . . . . . . . . 3-18 Tire Overloading . . . . . . . . . . . . . . . . . . . . . . . 3-18 Tire Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10 Tire Replacement . . . . . . . . . . . . . . . . . . . . . . 3-14 Tires . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13 Tire Size and Load Limits (G-Series) . . . . . . . 3-14 Tire Size and Load Limits (P-Series) . . . . . . . . 3-15 Tire To Rim Matching . . . . . . . . . . . . . . . . . . . 3-17 Tire Wear and Rotation . . . . . . . . . . . . 3-18,3-19 Toe-in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1 Torque Converter Clutch . . . . . . . . . . . . . . . . . 8-2 Torque Conversion Table (Appendix D) . . . . . A-19 Torque Values (Appendix C) . . . . A-11, A-12, A-13 Torque Wrerich Applications (Appendix C) . . . A-8 Torsional Isolator (Appendix 7-15) . . . . . . . . . 7-85 Towing . . . . . . . . . . . . : . . . . . . . . . . . . . . . . . . 1-3 Throttle Position Sensor (TPS) . . . . . . . . . . . . 7-34 Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1 Transmission Controls . . . . . . . . . . . . . . . . . . . 8-2 Transmission Failure (Appendix 8-1) .' . . . . . . . 8-7 Transmission Fluid . . . . . . . . . . . . . . . 8-3, 8-4, 8-7 Transmission Mounts . . . . . . . . . . . . . . . . . . . 8-5 Transmission Shifting . . . . . . . . . . . . . . . . . . . 8-5 Troubleshooting Aftermarket Fuel Systems (Appendix 7-8) . . . . . . . . . . . . . . . . . . . . . . . . . 7-50 Troubleshooting Heater and A/C Systems . . . 2-1 V U-Bolt Torque Specifications - Rear . . . . . . 3-12 Underinflation - Tire Wear . . . . . . . . . . . . . . 3-18 Underloaded Gears . . . . . . . . . . . . . . . . . . . . . 5-3 Universal Joint Failures . . . . . . . . . . . . . . . . . . 4-2 Universal Joints . . . . . . . . . . . . . . . . . . . . . . . . 4-1 Unleaded Gasoline . . . . . . . . . . . . . . . . . . . . . 7-22 V Vacuum Brake Bleeder (Appendix 6-2) . . . . . 6-13 Vacuum Modulator System . . . . . . . . . . . . . . . 8-2 Vacuum System Diagnosis - A/C . . . . . . . . . 2-5 INDEX (Cont'd) V (Cont'd) Vapor Lock Cause and Cure (Appendix 7-7) . . . . . . . . . . . . . . . . . . . . . . . . . 7-40 Vapor Vent Control Valve . . . . . . . . . . . . . . . . 7-96 Vehicle Emission Control Information Label 7-92 Vehicle Identification Number Codes . . . . . . . 1-2 Vehicle Identification Number (VIN) . . . . . . . . 1-2 Vehicle Load Conditions Shock Absorber . . . . . . . . . . . . . . . . . . . . . . . 3-10 Vehicle Ride and Handling Check . . . . . . . . . 3-11 Vehicle Ride Height . . . . . . . . . . . . . . . . . . . . . 3-9 Vibration Checks . . . . . . . . . . . . . . . . . . . . . . . 4-3 Viscosity - Oil . . . . . . . . . . . . . . . . . . . . . . . . . 7-7 Water in Fuel . . . . . . . . . . . . . . . . . . . . . . . . . 7-37 Weight Distribution (Appendix D) . . . . . . . . . A-15 Wheel and Stud Bolt Failures . . . . . . . . . . . . 3-16 Wheel and Tire Balancing . . . . . . . . . . . . . . . 3-14 Wheel Bearing Adjustment . . . . . 3-8, 3-9, 5-1, 5-2 Wheel Bearing Lubrication . . . . . . . . . . . . 3-8,5-2 Wheel Code and Limits - G-Series . . . . . . . 3-14 Wheel Code and Limits - P-Series . . . . . . . . 3-15 Wheel Nut Tightening Sequence . . . . . . . . . . 3-16 Wheels and Tires . . . . . . . . . . . . . . . . . . . . . . 3-13 Wheel Stud Bolt Replacement . . . . . . . . . . . . 3-16 Worn/Cracked Wheel Stud Holes . . . . . . . . . 3-16 <:~7 CHEVROLET WARRANTY COVERAGE RECAP Gee 1985 THRU 1994 LIGHT DUTY TRUCKS DEL.ON / AFTER 3/16/87 1988 1988 1987 1ST OWNER 1 ST OWNER 2ND OWNER 1992 & & 1994 2ND OWNER WITHOUT 2ND OWNER W/TRANS. TRANSFER W/TRANS . MTHS/MILE MTHS/MILE MTHS/MILE MTHS/MILES MTHS/MILE BASE WARRANTY (EXCEPT TIRES) ©' 36/36 36/50103 12/12 12/12 12/12 COVERAGE 1989 1990 1991 AIR CONDITIONING POWERTRAIN COMP . W/$100 DEDUCT AFTER 12/12 EMISSION PERFORMANCE WARRANTY DIESEL ENGINES W1100 DEDUCTIBLE AFTER 12112 7 12/12 12/12 12/12 12/12 36/50 14 12/UNLTD 12/UNLTD 12/UNLTD 12/UNLTD 12/UNLTD 12/UNLTD 12/UNLTD 36/36 15 36/50 72/60 24/24 72/60 24/24 72/60 24/24 60/50 60/50 24/24 72160 36/50 36150 60/50 6011008 60/50 3W508 60/50 72160 60/50 36150 Refer to policies & procedures manual to see if owner qualifies for 60150 coverage . With $100 deductible after 12112. First 12 months 1 unlimited mileage - no deductible. No deductible on portion factory installed = Condenser - Compressor. 1992 $100 deductible after 36136. 1987 1987 1987 I ST OWNER 2ND OWNER 2ND OWNER & 1985 WITHOUT 2ND OWNER WITHOUT 1986 TRANSFER W/TRANS. TRANSFER MTHS/MILES MTHS/MILES MTHS/MILES MTHS/MILE 36/36 15 See separate warranty folder. 1990-91 has 601100 warranty. DEL.BEFORE 3/16/87 60/50 ' 72160 60/50 36150 60/50 CQ7 CHEVROLET CHEVROLET MOTOR DIVISION General. Motors Corporation Technical service Department subject : G Dealer Service Bulletin AUTOMATIC APPLY PARKING BRAKE Model and Year : _ 90-391-5 Number : Section : 5 December 1990 Date : 065020 Corporate Bulletin No . : 1990 P3 MOTOR HOME (16,000# GVW ONLY) TO : ALL CHEVROLET DEALERS THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 90-367-5, DATED OCTOBER 1990 . THE MODEL DESIGNATION HAS BEEN CORRECTED . ALL COPIES OF 90-367-5 SHOULD BE DISCARDED. The parking brake system on the 1990 16,000 pound GVW P3 motorhome chassis incorporates a unique automatic apply feature with an internal expanding parking brake. The system is different than the 1989 and 1991 systems of the same model . The parking brake is spring applied and hydraulically released . Hydraulic pressure is supplied by the power steering pump. Full brake disengagement requires that 95-115 PSI pressure exists at the brake actuator . The parking brake can be applied by using a hand button or automatically when the shift lever is in the park position . The system features an HR-1 relay valve serving as a flow control point. The HR-1 reduces and directs flow to and from a spring actuator operating the parking brake (see Figure 1) . Operational Features 1. In the event the vehicle stalls, the wheels can be spun freely for at least ten minutes until pressure is drained from the brake actuator and the spring brake reapplies . 2. A parking brake light in the vehicle warns the operator when the brake is applied. This brake light will come on when the pressure at the actuator is less than 60 PSI . Parking Brake Adjustment 1. Adjusting the brake-to-drum clearance. Adjust screw through the drum opening until the brake just locks up . Back off the adjuster two to four notches . Chevrolet bulletins are intended for use by professional technicians, NOT a "dolt-yourselfer ." They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to yourvehicle, or that your vehicle will have that condition . See your Chevrolet dealerfor information on whether your vehicle may benefit from that information. GSD 148D Rev. 12/89 Drum should spin free with only light drag . 2. Adjusting the cable free play (see Figure 2) . Loosen the jam nut towards the brake actuator. Turn the 3-inch-long hex nut along the stud until no free play exists . Move the jam nut until it is against the 3-inch-long hex nut. The actuator should stroke between .75 and 1 .00 inch when properly adjusted . 3. Adjust the transmission linkage (see Figure 3) . Apply the parking brake. Loosen the screw (226) . Put the column selector lever in the neutral position . Put the lever into the neutral gate, do not use the indicator to find the neutral position. To put the transmission in neutral, move the shift lever (A) to the forward position, then back to the second detent . Hold the rod (240) tightly in the swivel (244). Tighten the nut (226) to 23 N.m (17 lbs. ft.) . Put the column selector lever in the "P" (park) position. Check the adjustment . The column selector lever must go into all positions. The engine must start in the "P" (park) or "N" (neutral) positions only . Bleed Procedure 1 1. Fill the power steering pump fluid reservoir to the proper level and let the fluid settle for at least a few minutes . 2. Start the engine and let it run for a few seconds ; then turn off the engine . 3. Add fluid, if necessary. 4. Repeat the above procedure until the fluid level remains constant after running the engine. 5. Block the rear wheels or raise them off the ground. 6. Raise the front of the vehicle,so the wheels are off the ground. 7. Start the engine, put the transmission in neutral, and place the park apply button in the release position. Slowly turn the steering wheel right and left, lightly contacting the ., wheel stops. 90-391-5 -38. . Check the fluid level and add fluid, if necessary. 9. Lower the vehicle and turn the steering wheel slowly from lock to lock. 10 . Stop the engine. Check the fluid level and refill as required . 11 . If the fluid is extremely foamy, allow the vehicle to stand a few minutes and repeat the above procedure. 12 . If air still remains in the system, proceed on to bleed procedure 2. Bleed Procedure 2 1: Secure the vehicle. 2. With the engine running, move the shift lever from the park to the neutral position. 3. Back off the bleed nut on the actuator and allow the system to self-bleed . 4. Tighten the actuator bleed part and cycle the system. 5. If air still remains in the system, proceed on to bleed procedure 3. Bleed Procedure 3 1. Secure the vehicle. 2: Crack open the exhaust fitting of the manual control valve . 3. Engage the parking brake using the manual control valve. 4. Allow a small amount of fluid to bleed out of the fitting, then quickly tighten the fitting . 5. Repeat bleed procedures 1-3, as required . Replacing the HR-1 Relay Valve 1. Removal Block the wheels and shut off the engine. Disengage the parking brake by running the actuator arm nut down against toe bracket retaining the stud in a released position . Mark all lines and fittings . " 2. Remove all lines from the HR-1 . Installation " Qonnect all lines to the HR-1 . Be careful to use the marks made upon removal. " Check fluid in reservoir . 90-391-5 Perform system tests outlined in this service bulletin . Move the dam nut until it is against the 3-inch-long hex nut. 3. Adjusting the transmission linkage . " Refer to the service manual. 1990 RN,G,P models 7A1-55 shift linkage adjustment. HR-1 Relay Valve Bleeding Procedure 1 " Secure the vehicle. " With the engine running, move the shift lever from the park to the neutral, position . Open the port on the actuator and allow the system to self-bleed . Tighten the actuator bleed port and cycle the system. " If a whine noise can be heard, air still remains in the system; proceed on to Bleeding Procedure 2. HR-1 Relay Valve Bleeding Procedure 2 Secure the vehicle. " Crack open the exhaust fitting of the manual control valve . " Engage the parking brake using the manual control valve. " Allow a small amount of fluid to bleed out of the fitting; then quickly tighten the fitting. " If air still remains in the system, bleed the power steering system as described in the service manual. DIAGNOSTIC INFORMATION : The following Diagnostics Charts 1 and 2 can be used to to determine if the Automatic Apply Parking Brake System is functioning normally and to identify what repairs may be required . 90-391-5 RESERVOIR MANUAL APPLY CONTROL VALVE SHIFT ACTUATED CONTROL VALVE Figure 1-Parking brake system Figure 2 NOTE: Improper adjustment of the park brake shoes or actuator can cause air noise in the power steering systems . Step 1 - Reference page 6-9 propeller shaft drum-type brake adjustment. Step 2 - Block wheels - Engine running - Park Position A - Check actuator cable length inside support bracket to #2 hex -nut. B - Block wheels - Engine running - Neutral Position CAUTION : Have someone in driver seat with service brake applied - recheck above cable length. Movement of cable should be 1 .20 inches to 1 .44 inches . Movement over 1 .44 inches will allow power steering reservoir to empty and draw air causing power steering noise after each cycle of the actuator (See Figure 2). A. B. 226 . 227 . 228. 229. 231 . 232. 238. 240. 241 . 242. 243. 244. SHIFT LEVER STEERING COLUMN SCREW RETAINING PIN NUT SPRING INSULATOR RETAINING PIN EQUALIZER LEVER ROD BEARING INSULATOR WASHER SWIVEL Figure 3 -Shift Linkage 90-391-5 -8- DIAGNOSTIC CHART 1 Secure the vehicle by blocking its front wheels . With the parking brake released turn off the engine . Jack up the rear and spin the propshaft . Propshaft will not spin freely at all . 1 . Bleed the system. 2 . Adjust the cable freeplay . 3. Adjust the brake to drum clearance . 4. Adjust the transmission linkage . Propshaft spins freely for at least 10 minutes. System functioning properly . OK System unchanged Check all lines and fittings for leaks and proper routing . Replace if necessary . OK System unchanged Inspect the brake actuator. Replace if necessary . OK System unchanged If the system is still not functioning properly the HR-1 relay valve is malfunctioning . Replace the HR-1 relay valve. Resume vehicle operation . 90-391-5 -9- DIAGNOSTIC CHART 2 Secure the vehicle by blocking its front wheels . Set the parking brake using the manual apply button . Propshaft spins freely with light drag . 1 . Bleed the system. 2 . Adjust the cable freeplay . 3 . Adjust the brake to drum clearance . 4. Adjust the transmission linkage . Propshaft will not spin . System functioning properly . OK System unchanged Check all hydraulic lines and fittings . Repair any leaks . Check lines for proper routing . OK System unchanged Inspect the brake actuator. Replace if necessary. OK System unchanged If the system is still not functioning properly the HR-1 relay valve is malfunctioning . Replace the HR-1 relay valve. Resume vehicle operation . 90-391-5 'CHEVROLET Ge CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department subject: HYDRAULIC FLUID/LEAKING HYDRAULIC PARK BRAKE VALVE SEAL Model and Year : Dealer Service Bulletin 90-435-5 Number : 5 Section : Date : OCT. 1991 165007 Corporate Bulletin No .: ASE No .: A5 1990 P316000 LB. MOTOR HOME (RPO C7P) Some owners of 1990 P3 16000# motor homes may experience a condition where the hydraulic park apply control valve leaks hydraulic fluid. This does not affect the parking brakes while they are applied . The cause may be an undersized O-ring which allows the fluid to pass out of the valve and/or a cap nut with insufficient thread which results in insufficient torque . For vehicles with the above condition, the O-ring and cap nut should be replaced and threaded surfaces torqued to the specifications listed below. Additional parts are provided in the repair kit and should be used if necessary. Note: Excessive torquing of the cap nut (Figure 1, View A, #4) may result in the crushing of the . bottom portion of the control valve. SERVICE PROCEDURE : (Figure 1) 1. Place transmission in park position, set manual appl park brake by putting manual control knob in the on position. Leave the ignition in the off position. Put locks on wheels. 2. Detach the left front wheel well panel. Retain all fasteners and panel for the reinstallation process. Locate the control valve (Figure 1). Prepare the removal area by having a towel or rag available to catch any oil leakage from the pipe/valve .during removal. 3. Detach the supply pipe assembly at the elbow fitting (#5) . Gently move pipe out of area to facilitate removal of the cap nut (#4) and elbow (Figure 1, View A, #5). The seal (#3) may not drop out due to oil viscosity; it may be necessary to use a thin pick to dislodge the seal (#3) from inside valve. Disconnect elbow from cap nut. 4. Prior to assembly, lubricate bores, O-ring, and threads with lubriplate (P/N 1050109) or equivalent . Install replacement O-ring (#3) over replacement cap nut (#4); place spring (#2) on inner pocket of cap nut (#4) and rest seal (#1) on top of the spring (#2) . Balancing this assembly, gently raise into the valve body. Upon making contact with the valve, hand tighten assembly. Then torque cap nut (4) to 6-16 N .m . (5-12 lbs. ft.) in proper alignment with supply pipe . 5. Apply thread sealant to threads going into cap nut (#4) and threaded surface of elbow (#5). Thread elbow (#5) into cap nut (#4) and torque elbow to 12-14 N.m. (9-10 lbs. ft.) . The final alignment of the elbow (#5) should be in the same direction as the plugged fitting located above the elbow (#5). CAUTION : Do not apply sealant over the elbow opening. 6. Reattach the supply pipe by gently bending it back into position ; insert pipe into the elbow (#5) and torque the nut to 12-14 N .m. (9-10 lbs. ft.). NOTE : To maintain proper fluid level throughout the bleed procedure,* check and fill the power steering reservoir as necessary with power steering fluid (P/N 1050017) . Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer," They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information. GSD 1480 Rev. 12189 7. Leaving vehicle transmission in park position, bleed system by starting vehicle and allowing 30 seconds to elapse ; then loosen the supply pipe nut just enough to allow air to escape the system . Prepare the area by having a towel or rag available to catch any oil leakage. When leakage occurs, retorque supply pipe nut to 12-14 N.m. (9-10 lbs. ft.). Put the manual control knob in "OFF" position, cak delivery ("0') fitting on manual control valve to bleed. Release and set the manual apply park brake s x times to help the bleeding process . Retorque delivery fitting of manual control valve. Turn off engine ; inspect valve and fitting for leakage; tighten as required . 8. Retrieve and reinstall retained fasteners and wheelhouse panel that were detached in Step 2. SERVICE PARTS INFORMATION: Part Number Description 15680238 1050109 1050017 NPN Seal Repair Kit Lubriplate Power Steering Fluid Teflon Tape Quantity 1 As Required As Required As Required Parts are currently available from GMSPO. WARRANTY INFORMATION : For vehicles repaired under warranty use: Labor Operation: T7296 Labor Time: 0.6 hr. NOTE : Labor Operation is coded to base vehicle coverage in the warranty system. 1. 2. 3. 4. 5. SEAL SPRING O-RING CAP NUT ELBOW PLUGGED FITTING (CONTROL VALVE) VIEW A 165007 Figure 1 Dealer Service Bulletin CHEVROLET Gam® CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department subject: 90-397-313 Number: Section : 313 January 1991 Date: POWER STEERING PUMP NOISE/HIGHER FLUID PRESSURE Model and Year: 1990 P3 MOTORHOMES (16000# GVW ONLY) TO: ALL CHEVROLET DEALERS Some of the above subject vehicles may experience higher noise due to vacuum buildup in the power steering reservoir. To correct this condition, it is necessary to replace the power steering reservoir cap with a new vented cap and install a longer vent hose with a new fastening clamp. SERVICE PARTS INFORMATION Part Number Description 26018909 15654401` 1648216 Cap Quantity Required Hose Clamp 1 1, 1 Hose must be cut to 870mm length for proper protection of radiator from vented fluid . Parts are currently available from GMSPO. Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer.' They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to yourvehicle, or that your vehicle will have thatcondition. See your Chevrolet dealerfor information on whetheryourvehicle may benefit from that information. GSD 148D Rev. 12/89 CHEVROLET CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department subject: AUTOMATIC/MANUAL APPLY PARKING BRAKE WILL NOT RELEASE/LEAKING POWER STEERING FLUID Model and Year: Dealer Service Bulletin 90-419-5 Number: Section :: Date: MAY 1991 065024R Corporate Bulletin No.: 1990 P3 MOTOR HOME CHASSIS Some 1990 P3 Motor Home Chassis 16000 Lbs GVW may experience fluid leaks near the hose clamps on the hydraulic manual apply park brake hose assembly. This will not allow the park brake to be released. This assembly was manufactured utilizing a hose and clamp assembly (Figure 1 A) . To correct the above condition, a new crimped hose assembly (P/N 26025331) has been released (Figure 1 B) . SERVICE PROCEDURE: (Figures 1A and 1B): DO NOT put transmission selector in "Park" position . Use Neutral . DO NOT set manual park apply (leave "park brake" control knob in the OFF position, brake not applied) . Ignition in the off position. Put blocks on wheels. 2. Remove the left front wheel well panel . Retain all fasteners and panel for the reinstallation process. Locate the return line hose from Figure 1A. Prepare the removal area by having a towel or rag available to catch any oil leakage from the hose during removal. 3 . Obtain the replacement hose (P/N 26025331) prior to removing the old hose assembly . 4. Remove the clamped hose assembly, catch as much fluid as possible . Remove the O ring seal from the steering gear. Reinstall new O ring seal (P/N 26001594). Carefully seat O ring in steering gear seat . Install new hose (26025331) at steering gear and finger tighten. Then install hose at relay valve ; again, finger tighten. 5 . Torque the tube nut at the steering gear to 20-34 N.m (15-25 Ibs. ft.) and the fitting at the valve assembly to 20-27 N.m. (15-20 lbs. ft.) (Figure 1 B) . 6. Bleed the power steering system. Using the procedures identified in the service manual for power steering ; purge the system of air. After completion of the bleeding procedure reinspect the hose for any oil leaks. Retorque as required . Reinstall the wheel well panel. Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer," They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information . GSD 1480 Rev . 11249 NOTE : Do not put transmission in "Park" position or apply manual control valve until after bleeding is completed . SERVICE PARTS INFORMATION : Part Number Description 26025331 Hose Assembly 26001594 0 Ring Parts are currently available from GMSPO. WARRANTY INFORMATION : For vehicles repaired under warranty use : Labor Operation : T7226 Labor Time: 0.7 hr. Trouble Code: 92 Quantity Required 1 (All P3 with 16,000 lb option C7P) 1 Installation Figure 1 B Removal Figure 1 A Relay Valve Assembly Relay Valve Assembly Remove relay valve inlet pipe assembly at tube nut and steering gear-nut. Remove O-ring Steering Gear Fitting Torque (20-27 N-m) Tube and Hose Assembly 26025331 Fitting Torque (20-34 N"m) Note : Seat O-ring prior to Installing hose fitting to steering gear 065024 Figure 1 CHEVROLET e® CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department subiw: Dealer Service Bulletin AUTO APPLY PARKING BRAKE MAY NOT RELEASE Model and veer: 91-240-5 Number: Section : 5 MARCH 1991 Date: 065022 Corporate Bulletin No .: 1990-91 P3 TRUCK Some 1990 - 1991 P3 Motorhomes with auto apply parking brake may not release. The cause may be loosening of the auto apply cable and/or the auto apply control valve. Follow the appropriate.service procedure that addresses the condition. AUTO APPLY CABLE ON 1990-91 P3 16,000# MOTORHOMES WITH C7P The auto apply control cable may loosen or pull through the attaching clip . This loosening can be corrected by the replacement of the clip (2058447) and the installation of a new washer (2436161). SERVICE PROCEDURE:(Figure 1): 1 . Place shift lever in park, turn ignition key to the off position . Block the wheels to prevent vehicle movement during servicing. 2. Locate the park brake control cable under the instrument panel adjacent to the steering column (Figure 1). 3. Remove the bolt holding the cable in place . Retain the bolt and nut for the reinstallation procedure. 4. Remove the cable clip from the cable and discard. Utilizing a new clip (P/N 343464) attach the cable to the bracket using the existing bolt and nut and a new washer (P/N 2436161) . Align the clip so that no kinking of the cable occurs during the tightening of the bolt and nut as shown in Figure 1 . 5. Torque the nut to 6 - 9 N.m. (4.5 to 6.6 lbs. ft.) . 6. Start the engine . Verify the vehicle's transmission is 'in the neutral position and the "park brake" Control is applied. Release the "park brake" control and observe that light on dash goes out. Reapply the "park brake" control and observe that park brake actuates . Also verify that park brake cable operates smoothly. 7 . Return vehicle to holding area ; service inspection work is completed. Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer." They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information can whether your vehicle may benefit from that information. GSD 148D Rev. 12189 SERVICE PARTS INFORMATION Part Number Description 2436161 343464 Washer Clip Quantity 1 (all P30032 at 16,000 lb, Option C7P) 1 WARRANTY INFORMATION Labor Operation: T7216' Labor Time: 0.2 hr. TROUBLE CODE : 92 AUTO APPLY VALVE BRACE ON 1990 P3 16,000# MOTORHOMES WITH C7P The auto apply control valve may loosen at the cam actuator arm . This condition can be corrected by the installation of a brace, (P/N 15666448). SERVICE PROCEDURE (Figure 2): 1 . Set parking brake, block wheels, ignition in the off position, and transmission in the park position . 2. Locate the park brake control valve on the left inside frame rail adjacent to the transmission shift control (Figure 2). 3. Remove the three bolts shown in figure 2., Discard the washers ; retain the 5/16" bolt and nut. Obtain two new nuts and bolts for the lower mounting attachment. 4. Install the new brace (P/N 15666448) towards the transmission on the control valve so that the brace faces inboard. Install the two new lower bolts and nuts as shown. Reinstall the existing upper bolt and nut. IMPORTANT Nuts and bolts must be installed as shown in Figure 2 with the nuts clamping against the new brace . 5 . Torque the two 1/4" nuts and the 5/16" nut to 6 - 9 N.m. (4 .5 to 6.6 lbs. ft). 6. With the vehicle in the park position, remove the wheel blocks, start the engine, release the manual park brake, and cycle the auto park apply system by moving the shift lever from park to drive . Observe that the vehicle's park brake functions properly. 7 . Turn off vehicle ; put on parking brake ; shift lever in park; inspect the control valve for any hydraulic leaks; torque fitting as required . SERVICE PARTS INFORMATION Part Number Description Quantity 15666448 Brace Park Brake 1 (all P30032 at 16,000, Control Valve option C7P) 9440148 Bolt 1/4"-20 X 2 .00" (GM 280-M) 2 9422273 Nut 1/4"-20 (GM 286-M) 2 WARRANTY INFORMATION Labor Operation : T7217' Labor Time : 0.5 hr. TROUBLE CODE : 92 AUTO APPLY VALVE BRACE ON 1991 P3 16,000# MOTORHOMES WITH C7P The auto apply control valve may loosen at the cam actuator arm . This condition can be corrected by the installation of a brace, (P/N 15666448) . SERVICE PROCEDURE: (Figure 3) 1 . Set parking brake, block wheels, ignition in the off position, and transmission in the park position . 2. Remove the left hand front splash shield, save all fasteners for reinstallation . Locate the park brake control valve on the left side above the steering gear (Figure 3) . 3. Remove the three bolts shown in Figure 3. Discard the three washers, two 1/4" and one 5/16" washer. Replace the two 1/4" bolts and nuts with new hardware . Reuse the 3/16" bolt and nut. 4. Install the new brace (P/N 15666448) on the control valve so that the brace faces outboard. Install the two lower bolts and nuts . Reinstall the upper bolt and nut. IMPORTANT: Nuts and bolts must be installed so that the nutsclamp against the new brace. 5. Torque the three nuts to 6 - 9 N .m. (4.5 to 6.6 lbs. ft.) . 6. Reinstall the splash shield . (figure 3). Reuse the fasteners ; torque to standard specifications 7. With the vehicle in the park position, remove the wheel blocks . Start the engine; release the manual park brake, and cycle the auto park apply system by moving the shift lever from park to drive. Observe that the vehicle's park brake functions properly. 8. Turn off vehicle ; put on parking brake ; shift lever in park. Inspect the control valve for any hydraulic leaks. Torque the fittings as required . -4SERVICE PARTS INFORMATION Part Number Description 15666448 Brace Park Brake 9440148 Bolt 1/4"-20 X 2.00" (GM 280-M) 9422273 Nut 1/4"-20 (GM 280-M) Quantity 1 (all P30032 at 16,000, Control Valve option C7P) 2 2 WARRANTY INFORMATION Labor Operation : T7218' Labor Time : 0.7 hr TROUBLE CODE : 92 ' NOTE: All Labor Operation are coded to base vehicle coverage in the warranty system . Parts are currently available from GMSPO. Existing Bolt/Screw (6-9 N-m) Figure 1-1990 Cable Clipping Control Valve Assembly Existing Nut and Bolt (6-9 N-m) New Nuts 9422273 (6-9 N-m) Assembly Note : All three brace retaining nuts and bolts must be installed so that the nuts clamp against the new brace . 065022 Figure 2-1990 Auto Apply Brace For P30032 With C7P 7_ Existing Nut and Bolt (6-9 N-m) New Nuts 9422273 (6-9 N-m) Assembly Note: All three brace retaining nuts and bolts must be installed so that the nuts clamp against the new brace . 065022 Figure 3-1991 Auto Apply Valve Brace For P30032 With C7P CHEVROLET CHEVROLET MOTOR DIVISION Gr-= General Motors Corporation Technical Service Department subject: Dealer Service Bulletin SERVICE ENGINE SOON LIGHT (CODE 22) Model and Year : 92-02-6E Number: Section : 6E AUGUST 1991 Date : 136514R Corporate Bulletin No . : 1991-92 CAPRICE AND CAMARO WITH 5.01- AND 5.71- ENGINES 1991-92 ALL TRUCKS WITH 3.1 L, 4.3L, 5.OL, 5.71- AND 7.41- ENGINES THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN 91-357-6E, DATED JUNE 1991 . THE VIN BREAKPOINTS HAVE BEEN ADDED AND THE BULLETIN NUMBERS WHICH WERE CANCELLED SHOULD READ 91-60-6E AND 91-333-7A . ALSO THE 1992 MODEL YEAR HAS BEEN ADDED . ALL COPIES OF 91-357-6E SHOULD BE DISCARDED . PLANT VIN BREAKPOINT SHREVEPORT 1 GCCSI4ZLM8177329 MORAINE 1 GNCS13ZLM2211006 PONTIAC 1 GCCT14Z5MO149156 This bulletin pertains to the 5.01- and 5 .71- engine for passenger cars and 4.3U3.1 L, 5.0U5 .7L and 7.41engines for light duty trucks. Condition Some owners of the above vehicles may comment on a Service Engine Soon Light - Code 22 Throttle Position Sensor low. Additional comments may include no upshift to 4th gear, no TCC, harsh transmission shifts, or poor idle quality. These conditions may be more prevalent after initial startup. Cause: The above concerns may result from an intermittent electrical contact inside the Throttle Position Sensor (TPS) . Correction : If any of the subject conditions are found, complete the following procedure : 1 . Perform the normal diagnostics per Section 6E of the Service Manual. 2 . Check TPS/ECM connectors per Dealer Service Bulletin No . 91-106-6E. 3. If no problems are found using the normal 6E diagnostics or the bulletin, replace the TPS with a new TIPS kit, P/N 17112679 per the procedure in Section 6E of the Service Manual . The new TPS will have a yellow dot at the connector area for easier identification . Part is currently available from GMSPO. Note : The lack of 4th gear, no TCC and harsh transmission shift concerns are only associated on truck applications with the HYDRA-MATIC 41-80-E (4 speed automatic) electronic transmission . Use applicable labor operations and times . Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer," They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information. GSD 148D Rev. 12/89 CHEVROLET Gas CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department Subject: BRAKE SQUEALINOISE Dealer Service Bulletin REVISED 91-151 A-5 Number : Section : AUGUST 1991 Date : 965016R Corporate Bulletin No.: ASE No.: Model and Year : 5 A5 1976-91 P3 MOTOR HOMES EQUIPPED WITH 4-WHEEL DISC BRAKES (RPO JF9) THIS BULLETIN REVISES DEALER SERVICE BULLETIN NO. 91-151-5, DATED JANUARY 1991 . REPLACEMENT OF BOTH FRONT AND REAR LININGS HAS BEEN SPECIFIED. ALL COPIES OF 91-151-5 SHOULD BE DISCARDED. A new brake lining service kit is available that contains brake pads constructed of a new compound developed to reduce brake noise and squeal . It is important to understand that the new pad material will not totally eliminate brake noise. It can, however, reduce the noises to a level which is more acceptable . The new brake lining service kit, GM Part Number 15649295 contains all components necessary to replace either the front or rear brake linings . To better resolve brake squeal and maintain the vehicle's originally designed brake balance (front to rear), both front and rear linings should be replaced at the same time . The new brake pads can be identified by the CBD812 edge code printed on the side of the pad material . SERVICE PARTS INFORMATION : Part Number Description 15649295 Brake Lining Service Kit Note : Use one kit per axle . Parts are currently available from GMSPO. WARRANTY INFORMATION : For vehicles repaired under warranty use : Labor Operation H0042 H0043 Location Front Rear Use applicable labor time guide for labor hours. Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer ." They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information. GSD 148D Rev. 12/89 ~CHEVROLET CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department Subject: GeO Dealer Service Bulletin CHANGE IN BRAKE EFFECTIVENESS AFTER DISC BRAKE ROTOR REFINISHING/PAD REPLACEMENT Model and Year: 91-133-5 Number : Section : 5 December 1990 Date: 075003R Corporate Bulletin No . : ALL PASSENGER CARS ALL LIGHT DUTY TRUCKS TO: ALL CHEVROLET DEALERS THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 90-316-5, DATED AUGUST 1990 . INFORMATION HAS BEEN ADDED REGARDING HUB AND ROTOR CLEANING, PROPER TORQUING TECHNIQUE., REVISED MACHINING TABLE, CHANGE SPECIFICATION FOR MAXIMUM SCORINGING DEPTH . THE 1991 MODEL YEAR WAS ALSO ADDED. ALL COPIES OF 90-316-5 SHOULD BE DISCARDED . Some comments have been received about a change in preceived braking effectiveness which occurs after rotors have been refinished and/or disc brake pads have been replaced . New lining materials have been formulated for increased lining life and to reduce brake squeal . Also, Federal regulations currently prohibit the use of asbestos in Original Equipment Manufactured (O .E.M .) front disc brake linings, and will totaly ban asbestos from all O.E .M. brake linings in the near future . Due to these changes, initial rotor surface finish is more critical than in the past, and is required for good brake performance . Following are some recommended actions/procedures to assure proper performance of the brake systems on all vehicles after rotor and/or pad service has been performed: When performing routine brake maintenance such as replacing worn disc brake pads or shoes, DO NOT refinish disc brake rotors or drums unless : A. There is a brake pulsation condition present, and this pulsation is found to be, caused by the brake rotors or drums, or B. ' The rotors and/or drums are excessively scored . Surface scoring that does not exceed 1 .2MM (0 .050 in .) on rotors or drums should not affect brake operation . Before removing rotors from the hub assembly, mark the rotor and on wheel stud so that the rotor may be re-installed in the same position . Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer, They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have thatcondition. See your Chevrolet dealerfor information on whether yourvehicle may benefitfrom that information . GSD 148D Rev. 12/89 If rotors are removed, it is very important that rust and scale be removed from the rotor and hub mating surfaces . Failure to do so may introduce excessive lateral runout when the rotor is mounted on the brake lathe, or when the rotor is re-installed to the hub. 2. When refinishing disc brake, rotors, it is important that the brake lathe be in good operating condition and that all tools or bits are sharp. Recommended vibration dampeners and/or adaptors should be used and should be clean and free of nicks (remember, 1988-91 W models require the use of an adaptor, J37160, because of the two-piece design). The following table shows the recommended procedure for rotor machining : Spindle Speed Depth of Cut (per side) Tool Cross Feed per Rev Vibration Damper Sand Rotors-Final Finish ROUGH CUT FINISH CUT 150 RPM 0.127mm (0 .005") 0 .152mm - 0.254mm (0 .006" - 0.010") Yes No 150 RPM 0.051 mm (0 .002") 0.051 mm (0.002")Max Yes Yes It is important that a rough and a finish cut be made . All brake lathes use a single-point cutting tool which is not capable of giving the necessary surface finish . A SECONDARY FINISHING OPERATION MUST BE PERFORMED TO OBTAIN THE NECESSARY SURFACE FINISH . An acceptable finish can be obtained using the Ammco Model 8350 Safe Swirl Disc Rotor Grinder, or equivalent, using 120 grit sandpaper and sanding each rotor surface with moderate pressure for a minimum of 60 seconds with the rotor turning at 150 RPM . An alternate method is to use a sanding block with 150 grit sandpaper . With the rotor turning at approximately 150 RPM, sand each side for a minimum of 60 seconds using moderate pressure . After the rotor has been sanded, the surfaces must be cleaned with a solvent such as brake cleaning, denatured alcohol, or equivalent . THE FINISHED ROTOR SURFACE SHOULD BE AS CLOSE TO THAT OF A NEW ROTOR AS POSSIBLE . FAILURE TO OBTAIN THE BEST POSSIBLE ROTOR FINISH WILL AFFECT INITIAL BRAKING PERFORMANCE. CAUTION : ROTORS OR DRUMS SHOULD ALWAYS BE REPLACED IF TURNING WILL RESULT IN A ROTOR OR DRUM THAT DOES NOT MEET MANUFACTURER SPECIFICATIONS FOR MINIMUM ROTOR THICKNESS OR MAXIMUM DRUM DIAMETER . NOTICE : When re-installing tire and wheel assemblies, it is very important that proper procedures be followed when installing and torquing the wheel nuts: A. Finger start all wheel nuts. B. Tighten wheel nuts .to specified torque (use the "star," or alternating nut pattern) using a torque wrench. DO NOT USE AN IMPACT WRENCH. UNEVEN AND/OR EXCESSIVE TORQUING OF THE WHEEL NUTS HAS BEEN FOUND TO DISTORT ROTORS, RESULTING 1N PREMATURE CUSTOMER COMEBACKS FOR BRAKE PULSATION 91-133-5 3. After brake pads have been replaced and/or rotors have been refinished, it is recommended that the new braking surfaces be broken in, or burnished, to properly seat them . This can be accomplished by making 20 stops from 30 mph, using medium to firm pressure . Take care to avoid overheating the brakes. 4. It is strongly recommended that the correct, specified General Motors replacement part(s) be used when servicing G.M . vehicles . General Motors does not test non-G .M. parts for proper performance on G.M . vehicles . Therefore, the use of non-G.M . parts may result in unacceptable vehicle performance . It is also important that the correct G M . part(s) be used in the correct G .M . application . For example, some 'A' model disc brake pads ('A' Heavy) will fit on 'C and H' models, but will not provide the same performance as the pads specified for use on C and H vehicles . It may seem preferable to stock fewer brake pad part numbers, but customer dissatisfaction may result if vehicle performance is affected . 91-133-5 CHEVROLET Gem CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department Subject: Dealer Service Update Bulletin AUTOMATIC TRANSMISSION DIAGNOSIS CHARTS UPDATED Model and Year: 91-210-7A Number : Section : 7A FEBRUARY 1991 Date : 177107R Corporate Bulletin No. : 1991 C/K, R/V, P AND G TRUCKS WITH 4L80-E/4L80-EHD AUTOMATIC TRANSMISSION SERVICE UPDATE BULLETIN COVERS : HYDRA-MATIC 4L80-E/4L80-EHD Transmission updates occurring after Service Manual printing . LIGHT DUTY TRUCK SERVICE MANUAL UPDATES : Automatic Transmission / Diagnosis Information : Range Reference Chart has been revised. (Figure 1) Wiring Diagram has been revised. (Figure 2) Remove Notice under Torque Converter Clutch (TCC) Diagnosis: Notice says: Do not bench test the TCC Solenoid using an automotive type battery. Accidentally crossed wires will damage the internal diode of the Solenoid . (This notice does not apply to the 4L80-E Transmission .) Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer," They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information. GSD 1481 Rev . 12189 HYDRA-MATIC 4L80-E - GEAR RATIOS FIRST 2 .48 FOURTH .75 REVERSE 2 .08 SECOND 1 .48 THIRD 1 .00 RANGE D LO ROLLER CLUTCH ON OFF HOLDING REVERSE ON OFF HOLDING 1st ON OFF HOLDING APPLIED * 2nd OFF OFF HOLDING APPLIED HOLDING APPLIED OVERRUNNING 3rd OFF ON HOLDING APPLIED APPLIED OVERRUNNING APPLIED OVERRUNNING 4th ON ON OVERRUNNING APPLIED APPLIED OVERRUNNING APPLIED OVERRUNNING 1st ON OFF APPLIED HOLDING APPLIED * 2nd OFF OFF APPLIED HOLDING APPLIED HOLDING APPLIED OVERRUNNING 3rd OFF ON APPLIED HOLDING APPLIED OVERRUNNING APPLIED OVERRUNNING 1st ON OFF APPLIED HOLDING APPLIED OFF OFF APPLIED HOLDING APPLIED 131 ON OFF APPLIED HOLDING APPLIED 2nd OFF OFF APPLIED HOLDING APPLIED - O INTERMEDIATE INTERMEDIATE SPRAG CLUTCH CLUTCH SOLENOID OB K2nd *HOLDING BUT NOT EFFECTIVE ON - SOLENOID ENERGIZED OFF - SOLENOID DE-ENERGIZED FOURTH CLUTCH OVERRUN CLUTCH OVERDRIVE ROLLER ROLLER SOLENOID OA GEAR APPLIED FORWARD CLUTCH DIRECT CLUTCH FRONT BAND APPLIED REAR BAND APPLIED APPLIED HOLDING HOLDING * APPLIED HOLDING HOLDING APPLIED " APPLIED HOLDING OVERRUNNING HOLDING APPLIED OVERRUNNING 0 THE SOLENOID'S STATE FOLLOWS A SHIFT PATTERN WHICH DEPENDS UPON VEHICLE SPEED AND THROTTLE POSITION . I T DOES NOT DEPEND UPON THE SELECTED GEAR . NOTE : DESCRIPTIONS ABOVE EXPLAIN COMPONENT FUNCTION DURING ACCELERATION . Figure 1- Range Reference Chart APPLIED 3- pppp . 1111 ,Ilililil~lilVil~ ~I I~~III~I~UI1I1 r~sa 1 ~- (C) +12V SHIFT SOLENOIDS-RED. (D) PSM-BLACK \~C (E) PSM-WHITE (B) \\\r (F) PSM-BLUE SOLENOID "B" GROUND-GREEN (A) SOLENOID "A" GROUND-BLUE (H) +5V TEMP. SENSOR-RED (G) TEMP . SENSOR GROUND-GREEN L (M) FORCE MOTOR-GREEN (L) FORCE MOTOR-BLUE /(K) 12V PWM SOLENOID-WHITE (J) PWM SOLENOID GROUND-BLACK Figure 2 - Wiring Diagram CHEVROLET CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department Subject : Ge® Dealer Service Bulletin ELECTRONIC AND ELECTRO-MECHANICAL INSTRUMENT CLUSTERS Model and Year : 91-150-8C Number : Section : 8C January 1991 Date : 068302 Corporate Bulletin No . : ALL LIGHT DUTY TRUCKS TO : ALL CHEVROLET DEALERS Chevrolet and AC Delco have formed a joint program designed to help dealers locate exchange instrument clusters . A service called the "Instrument Cluster Locator Line" has been established . For your regular service needs, you should contact the nearest AC Delco Service Center. If they do not have the required cluster, you should then use the Instrument Cluster Locator Line . To do so, call the Locator Line operator at (313) 974-0497 between 7 :30 and 4 :30 Eastern Standard Time. The following information is required : the name of the AC Delco Service Center previously contacted the part number of the unit needed your dealer name, address and telephone number the make and body style of the vehicle being repaired . The operator will then locate another AC Delco Service Center which has the required cluster and call you back that same day to let you know where the part can be found. You can then order the part directly from that Service Center. The part will be shipped within 24 hours and you will receive it within 48 hours. Please note that the Instrument Cluster Locator Line Program should only be used if the electronic or electro-mechanical cluster is not available from your local AC Delco Service Center. Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer." They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle . Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealerfor information onwhether your vehicle may benefit from that information. GSD 148D Rev. 12/89 =' :7CH EVRO LET Ge® CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department subiect: 90-421-6E Dealer Service Bulletin Number: Section : _ MAY 1991 Date : 136511 Corporate Bulletin No . : DETONATION AND/OR EXHAUST ODOR Model and Year : 6E 1990 C/K, R/V, G AND P TRUCK WITH 7.4L ENGINE Condition : Some owners of 1990 trucks with the 7.4L engine may comment of either detonation at highway speeds or exhaust odor (sulfur smell) at idle . Cause: The original spark advance and idle calibration may generate detonation or sulfur odor comments for a few isolated conditions. Correction : On trucks where these conditions can not be repaired using normal service procedures, a revised calibration PROM should be installed (See below) . Part Number Emission System 16165446 NA4 (above 8600 GVW) 16165447 NA4 (above 8600 GVW) PROM Broadcast SCANNER I.D . M40 (Auto) AYKK 5451 M20 (Manual) AYKL 5461 Trans. Parts are expected to be available on June 3, 1991 . Until then normal part orders will not be accepted by GMSPO. Only verifiable emergency VIP orders will be accepted . SPO will make every effort to obtain parts . All parts will be placed on 400 control to waive VIP surcharges. However, the part will be shipped premium transportation at dealer's expense. All other order types will be cancelled as incorrectly ordered while the 400 control is in place. Note : These PROMS SHOULD NOT BE USED on the Chevy "S .S." Labor Operation Number: T0500 Labor Time : .6 Hour Trouble Code : 92 Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer." They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle . Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information . GSD 148D Rev. 12/89 CHEVROLET GC® CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department subject: INOPERATIVE SPEEDOMETER Model and Year : Dealer Service Bulletin 90-368-8C Number: Section : 8C October 1990 Date : 063305R Corporate Bulletin No . : 1989-90 P3 (MOTOR HOME) CHASSIS TO : ALL CHEVROLET DEALERS Some 1989-1990 P3 motor home chassis (32) and commercial van chassis (forward control chassis - model 42) may experience inoperative speedometers . This condition can be caused by either inadequate engagement of the upper speedometer cable or a broken lower speedometer cable tip . To correct, it is necessary to install either a new upper or lower speedometer cable. The new upper speedometer cable has a longer shaft core tip to provide full engagement of the speedometer core tip between the Vehicle Speed Sensor (VSS) and speedometer head (part of the instrument cluster) . The lower speedometer cable has a metal tip replacing a plastic tip to help prevent tip breakage . Vehicle manufacturing breakpoint is listed below : 1 GBJP37N7L3321236 Prior to performing the installation procedures, verify if the condition experienced is the result of inadequate engagement of the upper speedometer cable. If an inadequate engagement condition is present, replacement of the upper speedometer cable is required . Inspect the lower speedometer cable for a broken tip at the speed sender generator. If broken, replacement of the lower speedometer cable is required . INSTALLATION INSTRUCTIONS : UPPER SPEEDOMETER CABLE REMOVAL AND REPLACEMENT (see Figure 1): 1. Disconnect the negative battery connection . 2. Set park brake and put transmission lever in park. 3. Disconnect and remove the upper speedometer cable from the speedometer head in the instrument cluster . Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer, They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described; DO NOT assume thatthe bulletin appliesto your vehicle, or that your vehicle will have thatcondition. See your Chevrolet dealer for information on whetheryour vehicle may benefitfrom that information. GSD 148D Rev. 12MO 4. On Commercial vehicles, disconnect the opposite end of the cable from the road speed sender generator located underneath the vehicle (outboard of the left hand frame rail and in back of the front axle). On Motor Homes, disconnect the opposite end of the cable located in the left hand frame rail across from the transmission . 5. Install the new upper speedometer cable into the instrument cluster and connect to speedometer head . 6. On Commercial or Motor Home vehicles, reconnect the opposite end of the cable to the vehicle speed sensor (VSS) . Route and attach cable to avoid kinking, chafing or high temperature areas . Clip at positioning cable . 7. Reconnect negative battery connection . 8. Check for proper operation of speedometer . LOWER SPEEDOMETER CABLE REMOVAL AND REPLACEMENT (see Figure 1) : 1. Disconnect the negative battery connection . 2. Inspect road speed sender generator for broken plastic speedometer cable tip. If broken, remove broken piece prior to installing new cable. 3. Disconnect the lower cable from the vehicle speed sensor (VSS) . 4. Disconnect the opposite end of the cable at the transmission and remove cable . 5. Reconnect the lower speedometer case to the VSS . 6. Reconnect cable at transmission end . Route cable to avoid kinks or chafing. 7. Reconnect negative battery connection . 8 ., Check operation of speedometer . SERVICE PARTS INFORMATION : Description 16154975 Upr Speedo , Cable Asm . 1 Commercial (42) with Gas Engines . 16154985 Upr Speedo Cable Asm . 1 Motor Home (32) with Gas Engines . 16155035 , Lwr Speedo Cable Asm . 1 (*) Motorhome(32)/Commercial (42) with Gas Engines, Auto . Trans . & Power Disc Brakes. 16155045 Lwr Speedo Cable Asm . 16155055 Lwr Speedo Cable Asm . 90-368-8c Qty. P3 Model Part No. (') Commercial (42) with Gas Engines & Manual Trans . 1 (') Motorhome (32)/Commercial (42) with Gas Engines & auto. Trans . & Hydraulic Brakes. P/N P/N P/N P/N P/N 16154975 16154985 16155035 16155045 16155055 Use Use Use Use Use with with with with with RPO's LB4/1-05/1-19. RPO 1-19. RPO's 1-134/1-05/1-19 and M40 and JB7/JB8. RPO's LB4/1-05 and M20 . RPO's 1-05/1-19 and M40 and JF9 . RPO CODES: LB4 = 4.31- Gas Eng. 1-05 = 5.71- Gas Eng . 1-19 = 7.41- Gas Eng . M20 = 4-Spd. Man. Trans . M40 = 3-Spd . Auto. Trans. JB7 = Power Disc, Drum 8400 Lbs. JB8 = Power Disc, Drum 10000 Lbs. JF9 = Hyd. Brake, 4 Wheel Disc MODEL CODES: 32 = Motor Home Chassis 42 = Commercial - Forward Control Chassis Parts are currently available from GMSPO. WARRANTY INFORMATION For vehicles repaired under warranty use: Labor Operation Description N4382 N4383 R & R Upper Speedometer Cable R & R Lower Speedometer Cable Labor Time Use applicable Labor Time Guide for labor hours. 90-368-8C Figure 1 1990 - The vehicle speed sensor is located on the LH frame rail in the speedometer cable . 1991-1994 - The cruise control receives its signal from the drac module located on the LH side of the steering' column . 90-368-8C P/N P/N P/N P/N P/N 16154975 16154985 16155035 16155045 16155055 Use Use Use Use Use with with with with with RPO's 1-134/1-05/1-19 . RPO L19. RPO's 1-134/1-05/1-19 and M40 and JB7/JB8. RPO's 1-134/1-05 and M20. RPO's 1-05/1-19 and M40 and JF9. RPO CODES : LB4 = 4.31- Gas Eng . 1-05 = 5 .71 Gas Eng. 1-19 = 7 .41- Gas Eng. M20 = 4-Spd. Man . Trans . M40 = 3-Spd. Auto . Trans . JB7 = Power Disc, Drum 8400 Lbs. JB8 = Power Disc, Drum 10000 Lbs. JF9 = Hyd. Brake, 4 Wheel Disc MODEL CODES : 32 = Motor Home Chassis 42 = Commercial - Forward Control Chassis Parts are currently available from GMSPO. WARRANTY INFORMATION For vehicles repaired under warranty use : Labor Operation Description N4382 N4383 R & R Upper Speedometer Cable R & R Lower Speedometer Cable Labor Time Use applicable Labor Time Guide for labor hours . 90-368-8C REINSTALL TO TRANSMISSION 0 1 FRAME RAIL FRT LOWER CABLE PARK BRAKE CABLE / Figure 1 1990 - The vehicle speed sensor is located on the LH frame rail in the speedometer cable . 1991-1994 - The cruise control receives its signal from the drac module located on the LH side of the steering' column . 90-368-8C / VEHICLE SPEED SENSOR CHEVROLET Gea CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department subject: NEW STYLE HOSE CLAMP Model and Year : Dealer Service Bulletin 92-03-68 Number : Section: 6B AUGUST 1991 Date : 166201 Corporate Bulletin No .: 1983-92 ALL C/K AND 1987-92 R/V TRUCKS WITH 4.3L, 5.OL, 5 .7L, 6.2L, 7 .4L ENGINES A new design hose clamp will be used in production starting , with the 1992 model year on C/K trucks . Usage of this clamp will expand to include other models in the 1993 model year. The Mubea constant tension hose clamp was designed to reduce the amount of coolant leakage from radiator and heater hoses. With the previous design, screw type clamps, it is difficult to maintain a constant load on the hose connection . Some of the load is lost under certain temperature changes . The Mubea clamp exerts a relatively even and constant pressure that is maintained under varying temperature conditions. SERVICE PROCEDURE : o The- Mubea clamp must be installed on a hose which will be put on to a clean, dry, paint free surface. If lubrication is necessary for assembly, only GM lubricant P/N 998562 may be used . 9 Production of trucks with the clamp began 02/91, starting with the water pump and radiator connections. The heater hoses will follow in some applications . If the vehicle was originally built with Mubea clamps, the clamp should be replaced with the same P/N Mubea clamp and not a screw type hose clamp. 9 Also if the vehicle was originally built with screw/worm type clamps, the clamps should be replaced with screw/worm clamps. Note: Standard pliers or hose clamp pliers will not work well on the new style clamp. Various tool companies have developed special pliers to install and remove these hose clamps. Some companies may have a plier available that is effective in removing the larger size clamps but may not open wide enough to accommodate the clamp once it is off the hose and relaxed. Do not compress the clamp (permanently) to make the tool fit it, since this will decrease the effectiveness of the clamp . GMC does not endorse any specific tool or company. Check with local sources to determine availability. Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer," They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information. GSD 148D Rev. 12189 PARTS INFORMATION : Mubea clamps will be used in the following applications : Size Part Number Application 27mm 24mm 10108255 10146975 Heater Hoses Heater Hoses 42mm 50mm 55mm 15671833 10108249 156,71832 Radiator/Water Pump Hoses Radiator/Water Pump Hoses Radiator/Water Pump Hoses Note : The clamp's size is stamped on the tab of the clamp. Parts are currently available from GMSPO. WARRANTY INFORMATION : For vehicles repaired under warranty use : Labor Operation : J3340 ~7 CHEVROLET . CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department subject: Ge® CRUISE CONTROL CABLE REPLACEMENT Model and rear : Dealer Service Bulletin 91-137-9 Number : Section 9 December . 1990 Date : 069001 Corporate Bulletin No.: 1990-91 P3 MODELS TO: ALL CHEVROLET DEALERS A replacement cruise control servo cable for 1990 and 1991 P3 models with factory installed cruise control has been released by GMSPO . It will no longer be necessary to purchase a module and cable assembly if just a cable is required (see Figure 1) . The part number for a cruise control servo cable without the module for the P3 models mentioned is 25075767 . Parts are currently available from GMSPO. replacement cable 92 - 25075767 93 - 25140500 94 - 25140187 module assembly 90-92 - 25075766 93 - 25140082 94 - 25075219 Chevrolet bulletins are intended for use by professional technicians, NOT a °do-jtyyourselfer." They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely . If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whetheryour vehicle may benefit from that information. GSD 148D Rev . 12/89 Cruise Control Module/Cable P-3 Motorhome Chassis Figure 1  .137-9 069001 ~ CHEVRDLET CHEVROLET MOTOR DIVISION a® General Motors Corporation Technical SKvl e Department subject: 92-12-7A Dealer Service Update Bulletin Number: Date: SEPT 1991 177123 Corporate Bulletin No .: REUSABLE BOTTOM PAN SEAL Model and Year: 7A Section: ASE No .: A2 1991-92 C/K, RN, G AND P3 TRUCK WITH 41-80-E/4L80-EHD AUTOMATIC TRANSMISSION SERVICE UPDATE TRANSMISSION APPLICATIONS : 1991-92 HYDRA-MATIC 41-80-E/4L80-EHD (MT 1) SUBJECT: Reusable Bottom Pan Seal (Service Manual Information) TRANSMISSION MODELS : All Models VEHICLE APPLICATIONS : C/K, RN, and P- Trucks, G-Van Service Information : (Figure 1) The HYDRA-MATIC 41-80-E transmission bottom pan seal (29) is REUSABLE . When removing the bottom pan (28), it is recommended to inspect the seal for any possible leak points that may cause future concerns: " Tears in the rubber bead. " Missing torque limiters or washers. Broken carrier seal . If no signs have been found, then clean off seal with a clean soft cloth . Clean case and pan areas with part solvent before reinstalling seal . 27 BOLT, HEX FLANGE HD (PAN TO CASE) 28 PAN, TRANSMISSION OIL 29 SEAL, TRANS. OIL PAN Figure 1 Chevrolet bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer .' They are written to inform these technicians of conditions that technicians have the equipment, may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle . Properly trained DO NOT assume that the bulletin applies to your If a condition is described, a job properly and safely . safety instructions, and know-how to do tools, your vehicle may benefit from that information. for information on whether . See your Chevrolet dealer vehicle, or that your vehicle will have that condition GSD 148J Rev. 12189 4,D7 CHEVROLET CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department Sublecr Dealer Ge Service Bulletin 93-s7-6A Number : 6A Section : Date: NOV 1992 268304 Corporate Bulletin No . : INCORRECT OR ERRATIC OIL PRESSURE READINGS ASE No . : Model and Year: A1, A8 1990-93 ALL LIGHT DUTY TRUCKS Owners of some 1990 through 1993 light duty trucks may comment that the oil pressure dash gage reads high, has erratic movement or is inoperative. The internal resistance wire in the oil pressure sensor may not be properly supported, resulting in an intermittent open condition . Service Procedure: Check for normal causes of high oil pressure gage readings (high resistance or open circuit), such as a poor ground path caused by loose sensor mounting, oil cooler adapter loose, or poor electrical connections. If no cause can be found, replace the oil pressure sensor following the procedure below. 1 . Disconnect the negative battery cable. 2. Remove the wiring harness connector from the oil pressure sensor. 3. Remove the oil pressure sensor. 4. Install the new oil pressure sensor. 5. Connect the wiring harness connector to the oil pressure sensor. 6. connect the negative battery cable. Parts Information : . New Oil Pressure Sensor Part Numbers for the 1990-1993 models are: Model S/T Engine(s) L38/LN8/L35 1-1-2/1-134 M/L LN8/L35/1-134 En ine VIN Codes New P/N Replaces A,E,W 10201490 10201490 1647135 -90/91 10096178-92/93 R,Z 10201491 10201491 1647136 -91/92 10096179-92/93 . E,W,Z 10201496 10201490 1647135 -90/91 10096178-92/93 COPYRIGHT 1992 " CHEVROLET MOTOR DIVISION " GENERAL MOTORS CORPORATION " ALL RIGHTS RESERVED .* They are written to inform these technicians of conditions that bulletins are intended for use by professional technicians, NOT a 'do-it-yourselfer Chevrolet may occur on some vehicles, or to provide information that could assist in .the proper service of a vehicle . Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition . See your Chevrolet dealer for information on whether your vehicle may benefit from that information . GSD 148D Rev . 12189 Engines) Engine VIN Codes New P/N Replaces All Gas 10201489 Z,H,K,N 10068563-90/91 10201489 10137652-92/93 All Gas Z,H,K,N 10201489 10201489 10068563-90/91 10137652-92/93 All Gas K,N 10201489 10201489 10068563-90/91 10137652-92/93 P (60 psi) All Gas Z,K,N 10201489 10201489 10068563-90/91 10137652-92/93 P (80 psi) All Gas Z,K,N 10201490 10096178-92/93 Model C/K Parts are currently available from GMSPO Warranty Information: For vehicles repaired under warranty use labor operation N2220. 4D7 CHEVROLET CHEVROLET MOTOR DIVISION General Motors Corporation Teohntcal Service Department Subject: Ge® Dealer Service Bulletin REVISED 91-234A-OB Number: oB Section : Date: JULY 1992 166001R Corporate Bulletin No.: NEW DESIGN SPARK PLUGS A1, A8 ASE No .: Model and Year : 1991 ALL PASSENGER CARS AND TRUCKS WITH CPC GAS ENGINES THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN 91-234-0B, DATED MARCH 1991 . UPDATED TOOL INFORMATION IS BEING PROVIDED . ALL COPIES OF 91-234-OB SHOULD BE DISCARDED . In 1991 GM introduced a new design spark plug for use in all trucks equipped with gas engines. These new design spark plugs have a ceramic insulator which is approximately, 1 /8 inch longer than the insulator used in previous model years. The longer length spark plugs, which conform to S.A .E. and I.S .O. Engineering guidelines, magnify the problem of cracked insulators because currently, most spark plug sockets are not of sufficient length to properly engage the shell hex. If the spark plug shell hex is not fully engaged in the spark plug socket wrench, the socket may cock at an angle and cause insulator cracking and/or breakage during plug installation or removal. When servicing these new design spark plugs, make sure that the spark plug socket being used is deep enough to accommodate the longer length insulator. The spark plug socket wrench should conform to the proposed S.A .E. and I.S .O. world standards for spark plug socket wrenches . Spark plug socket wrenches that conform to these standards are designed to accept 'the lengthened spark plugs and allow full engagement of the hex nut on the shell of the spark plug . Use of a spark plug socket which is NOT deep enough may result in the ceramic insulator becoming cracked above the spark plug shell. Note : SOME CRACKS IN THE INSULATOR MAY NOT BE VISIBLE. SUCH CRACKS MAY LATER CAUSE A SPARK PLUG TO MISFIRE. SPARK PLUG MISFIRES ARE OFTEN MISDIAGNOSED AS A SLIPPING TRANSMISSION, DEFECTIVE TORQUE CONVERTER CLUTCH, ENGINE IMBALANCE, OR MALFUNCTIONING FUEL SYSTEM . To prevent insulator damage, it is recommended that the proper spark plug socket wrench be used when removing or replacing spark plugs. One such spark plug socket is the Kent-Moore J-39358 spark plug socket. The tool is available from Kent-Moore . For ordering information call 1-800-345-2233 or write : Kent-Moore SPX Corporation 39784 Little Mack Roseville, MI 48066-2298 Fax : 313-774-9870 Chevrolet bulletins are intended for use by professional technicians, NOT a 'do-it-yourselfer .' They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle . Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information. GSD 1480 Rev. 12/89 CHEVROLET MOTOR DIVISION General Motors Corporation Service Oaparlmanr Subject: CHEVROLET SERVICE Chevrolet Dealer Service Bulletin 88-283-6E Number: Section : 6E Date : ELECTROSTATIC DISCHARGE DAMAGE Model and Year: 1988 UP PASSENGER AND LIGHT DUTY TRUCKS WITH AN ELECTRONIC CONTROL MODULE (ECM) TO: ALL CHEVROLET DEALERS Please add the following information to 6E Section "A"Diagnostic Charts/Trouble Codes, and to Section "C1 " Electronic Control Module and Sensors . NOTICE : To prevent possible Electrostatic Discharge damage : , - Do Not touch the ECM connector pins or soldered components on the ECM circuit board . - When handling a PROM, CAL-PAK or Mem-Cal, Do Not touch the component leads, and Do Not remove integrated circuit from carrier . Electronic components used in control systems are often designed to carry very low voltage, and are very susceptible to damage caused by electrostatic discharge . It is possible for less that 100 volts of static electricity to cause damage to some electronic components . By comparison, it takes as much as 4,000 volts for a person to even feel the zap of a static discharge . There are several ways for a person to become statically charged . The most common methods of charging are by friction and by induction . An example of charging by friction is a person sliding across a car seat, in which a charge of as much as 25,000 volts can build up. Charging by induction occurs when a person with well insulated shoes stands near a highly charged object and momentarily touches ground. Charges of the same polarity are drained off, leaving the person highly charged with the opposite polarity. Static charges of either type can cause damage, therefore, it is important to use care with handling and testing electronic components . Chevrolet bulletins are intended for use by professional technicians, NOT a 'do-it-yourselfer .' They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safety. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information . GSD 148D Rev. 12189 A A. INSTRUMENT CLUSTER. GASOLINE ENGINE B. INSTRUMENT CLUSTER. DIESEL ENGINE Lam' CHEVROLET CHEVROLET MOTOR DIVISION Teehniod Service Deparhnent subject: Gee FACTORS THAT AFFECT FUEL ECONOMY Model and Year : ALL YEARS ALL MODELS Dealer Service Bulletin 93-96-6C 6C FEB. 1993 Dar.: 306502 Cam BuAelln No. : A1 . A8 ASENo. : BACKGROUND INFORMATION: EPA fuel economy estimates are posted on the fuel economy label of all new vehicles. The only intended use of these values is for comparison among the different vehicles. Fuel economy estimates are generated from data taken during a laboratory test using pre-production prototype vehicles underextremely controlled conditions using a professional driver, with the vehicle operating on an instrument similarto atreadmill . The comparisons of current vehicle fuel economy to the EPA fuel economy estimates is a misuse of the information and should be discouraged. The EPA GAS MILEAGE GUIDE, available at each dealership, points out that the actual mileage when driving a vehicle may differconsiderably from the estimated mileage. The guide also describes how vehicles are tested under identical conditions to insure the results can be compared with confidence . The EPA GAS MILEAGE GUIDE also points outthat styfuel economy estimate simulates a 7.5 mile, stop-and-go trip with an average speed of 20 mph. The trip takes 23 minutes and has 18 stops. About 18 percent of the time is spent idling, as in waiting at traffic lights or in rush hour traffic. Two kinds of engine starts are used - the cold start, which is similar to starting a car in the morning after it has been parked all night - and the hot start, similarto restarting a vehicle after it has been warmed up, driven and stopped for a hort time. The test to determine the highway fuel economy estimate represents a mixture of "non-city" driving. Segments corresponding to different kinds of rural roads and interstate highways are included. The test simulates a 10 miletrip and averages 48 mph. The test is run from a hot start and has little idling time and no stops. The EPA GAS MILEAGE GUIDE explainsthat the actualtest resultsare aclusted downward to arrive attheestimates used in the booklet and on the labels. City estimates are lowered by 10 percent and the highway estimate by 22 percent from the laboratory test results. The guide also points out that traveling at higher speeds lowers fuel economy and traveling at 65 mph instead of 55 mph lowers fuel economy over 15 percent . FACTORS THAT AFFECT FUEL ECONOMY : We Ratio Numerically lower axle ratios generally produce better highway fuel economy. The exception to this is if the engine is "working" exceptionally hard, (heavy vehicle loads pulling a trailer, small engine in a large vehicle ...). In these cases a numerically higher axle may provide betterfuel economy. Numerically higher axle ratios will also tend to provide more fuel economy in congested city traffic and stop and go conditions. Chevroletbulletins are Intended foruse by professional technicians, NOTa 'dodtvourselfer.' they arewrittento Inform thesetechniciansof conditions that ffx:n occur on sornevehicles, or to provide Information that could assist In theproper service of a vehicle. Property trainedtechnicians have the equipment, tools the btAotln appRes to your veMcie, or tho safety Instructions, will and know-how to do ajobproperly and safely. If e condition is described, DO NOTassume that your vehicle have that condition. See your Chevrolet dealer for Information on whetheryour vehiclemay bonetlt from that Information. Rev . 01 /9: Brake drag (even a minimal amount undetectable by coasting), can have a significant negative impact on fuel economy. Pull upward on the brake pedal to assure that the stoplight switch and cruise switch at the brake pedal are full and properly adjusted . A "lick" sound when'the pedal is pulled upward indicates that the switch was improperly adjusted . This causes the front brake pads to lightly rub the rotors, causing a fuel economy loss, without generating excessive heat or brake pad wear. Driving Habits Frequent short trips (less than 5 miles), especially in cooler ambient temperatures (less than 65 degrees), will necessitate fuel enrichment on start-ups, especially after "soaks* with the engine off for approximately a half hour or more. Frequent accelerator pedal movement while driving will reduce fuel economy because of fuel enrichment during the periods of acceleration. Undersuch driving conditions the torque converter clutch (TCC) alsodisengages, contributing to fuel economy losses . Prolonged idle periods reduce fuel economy especially in cold amblents when vehicle is allowed to "warm up" . Fuels Oxygenated fuels, with methanol and/or ethanol blended into the gasoline have lower energy and thus reduce fuel economy . Typically there is about a 1 MPG penalty for a vehicle which gets 25 to 30 MPG on 100 percent gasoline. Usingfuelsof alower octane thanthe vehidewascalibrated towillcause increased"KS"Knock Sensorsystem activity. This will result in a net decrease in spark advance and thus poorer fuel economy. Using fuel of a higher octane than the vehicle was calibrated for WILL NOT increase fuel economy . Variations in how muchfuel is added tothefuel tankduring re-fueling can greatly affect calculatedfueleconomy . These effects decrease as the distance traveled and the number of tank fillups increase . Green Engjne New vehicles have not yet had an opportunity for the engine to break in, (rings toseat...). A typical engine will take 3 to 5 thousand miles to break in and during this time period a gradual increase in fuel economy can be expected. Parasitic Loads Air conditioning and/or electrical loads, (headlights, heated badkglass . ..) also result in lower fuel economy, (typically less than 1 MPG difference, each 10 AMPs takes approximately .4 MPG). Road Conditions Road surface condition impacts fuel economy . Gravel and/or pot holed roads decrease fuel economy . Hills (vs. level terrain) also negatively impact fuel economy. Even gradual unperceptible increases in elevation result in real measurable decreases in fuel economy . Similarly, driving in the rain or snow decreases fuel economy . Vehicle suspension misalignment can cause poor fuel economy . Check all four tires for abnormal and/or premature tire wear. New tires, tire rotation, and/or front end alignment may be required to correct fuel economy . .L1L¢IZ Performance tires and/or tires with larger "contact areas," (like 60 series aspect ratio), can cause as much as 3 MPG -3 lower fuel economy when compared to hard "thin" tires. Find out if the tire size currently on the car is the same as original equipment . Replacement tires taller than original equipment tires cause the odometer to read LESS THAN actual distance traveled. This will result in lower calculated fuel economy than actual fuel economy . Tire Pressure Harder tires, (more air pressure, or different tire compositions) result in better fuel economy . Do not exceed maximum pressure as labeled on the tire, typically 30-35 psi . The disadvantage of this is that the greater the tire pressure, the harsher the vehicle ride. Transmission On 4-Speed automatics, it is possible to drive the vehicle in 3rd gear rather than "overdrive" and not perceive it. Typically this condition occurs when the shift indicator, or the shift linkage/detent is misadjusted . Misaclusted shift linkage can also result in improper signals to the ECM, which can result in less spark advance, and results in a drop in fuel economy. Driving a vehicle in 3rd gear rather than overdrive at highway speeds typically results in a 3 to 5 MPG penalty . Torque Converter Clutch operation isessential for goodfuel economy. A non-locking torque converter typically results in a 1 to 2 MPG penalty at highway speeds . Vehicle Weight Each 125 lbs . of additional weight results in a .3 MPG loss of fuel economy. Thus, additional passengers, luggage ... will decrease fuel economy . Vehicle Wind Resistance More wind "DRAG" means less fuel economy . Thus, hang-on luggage carriers, cat toppers, open windows and/or open trunk... mean less fuel economy . (See "Driving Habits"). 4Z~7 CHEVROLET CHEVROLET MOTOR DIVISION General Motors Corporation Technical Service Department subiect: Gas Dealer Service Bulletin OIL PRESSURE GAUGE READS HIGH 92-46-6A Number: Section: Date: NOV. 1991 168302 Corporate Bulletin No .: ASE No.: Ntodel and Year : 6A A1, A8 1991-92 P TRUCKS (MODEL 32 AND 42) WITH 4.31_(1_134), 5.71 . (1_05), 7.41_ (1_19) Some 1991-1992 P30 (32 and 42) with gasoline engines may show high oil pressure on the dash gauge. This condition is present only on the upper range of the oil pressure gauge (oil pressure will reflect correct readings in the lower and midrange on the scale of the gauge) . This high oil pressure reading may be caused by an incorrect oil pressure sending unit. Some vehicles were built with a 60 lb. sending unit instead of the correct 80 lb. sending unit. To correct, it will be necessary to inspect the oil pressure sending unit to determine if it is the incorrect sending unit. This can be confirmed by the stamping on the sending unit. The incorrect sending unit (P/N 10068563) is stamped 563. The CORRECT sending unit (P/N 10096178) is stamped 178 . SERVICE PROCEDURE : Tools Required : J35749 Oil Pressure Sensor Socket or equivalent. Inspection 1 . Inspect the side of the sending unit for the stamping number. Note : using a mirror to locate the stamping number may ease the inspection process. 2. If the sending unit is stamped 563, it should be replaced with the correct sending unit (P/N 10096178) using the procedure below. Replacement of the Sending Unit 1 . Disconnect the negative battery cable. 2. Remove the wiring harness connector from the oil pressure sending unit. 5.71_ and 4.31_ engines-the oil pressure sending unit is located at the left front side of the distributor. ' 7.41- engines-the oil sending unit is located at the front left side of the block. 3. Remove the oil pressure sending unit using tool J35749 or equivalent . 4. Install the oil pressure sending unit (P/N 10096178) using tool J35749 or equivalent . 5. Connect the wiring harness connector to the oil pressure sending unit. 6 . Connect the negative battery cable. Chevrolet bulletins are intended for use by professional technicians, NOT a -do-it-vourselfer .' They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See your Chevrolet dealer for information on whether your vehicle may benefit from that information . GSD 1480 Rev. 12J89 SERVICE BULLETINS AND GENERAL INFORMATION 90-391-5 - Automatic Park 90-435-5 - Automatic Park 90-397-3 - Automatic Park 90-419-5 - Automatic Park 91-240-5 - Automatic Park 92-02-6E - Service Engine Light 91-151A-5 - Brake Squeak 91-133-5 - Brake Disc Rotor Refinish 91-210-7A - 4L80E Transmission 90-421-6E - Detonation - Exhaust Odor 90-368-8C - Inoperative Speedometer 92-03-6B - New Hose Clamps 91-137-9 - Cruise Control 92-12-7A - 4L80E Pan Gasket 93-57-6A - Incorrect Oil Pressure Readings 91-234A-OB - New Design Spark Plugs 88-283-6E - Electostatic Discharge Damage 93-96-6C - Factors Effecting Fuel Economy 92-46-6A - Oil Pressure Gauge Reads High OPERATING TEMPERATURES Engine Oil - Page 7-8 Normal engine oil temperature in between coolant temperature and 50 degrees above . Coolant Temperature - Oil pressure 30 to 40 PSI while driving under operating temperature and moderate road speed . Engine Coolant - Minimal operating temperature 200 0 . Redline is 240° with 195° thermostat. Transmission Oil - Page 8-9 .