Recent Service Or Accident Repair:
Determine if any recent service has been performed on vehicle that may effect cooling system. This may be:
- Engine adjustments
- Slipping engine accessory drive belt(s)
- Brakes (possibly dragging)
- Changed parts. Incorrect water pump or pump rotating in wrong direction due to accessory drive belt not correctly routed
- Reconditioned radiator or cooling system refilling (possibly under filled or air trapped in system).
NOTE:
If investigation reveals none of the previous items as a cause for an engine overheating complaint, refer to COOLING SYSTEM DIAGNOSIS CHART
.
These charts are to be used as a quick-reference only.
COOLING SYSTEM DIAGNOSIS CHART
| CONDITION | POSSIBLE CAUSES | CORRECTION |
|---|---|---|
| TEMPERATURE GAUGE READS LOW | 1. Vehicle is equipped with a heavy duty cooling system. | 1. None. System operating normally. |
| 2. Temperature gauge not connected | 2. Connect gauge. | |
| 3. Temperature gauge connected but not operating. | 3. Check gauge. Refer to Electrical - Instrument Cluster/Instrument Cluster - Diagnosis and Testing | |
| 4. Coolant level low. | 4. Fill cooling system. Refer to Standard Procedure . | |
| TEMPERATURE GAUGE READS HIGH. COOLANT MAY OR MAY NOT BE LEAKING FROM SYSTEM | 1. Vehicle overloaded, high ambient (outside) temperatures with A/C turned on, stop and go driving or prolonged operation at idle speeds. | 1. Temporary condition, repair not required. Notify customer of vehicle operation instructions located in Owner's Manual. |
| 2. Temperature gauge not functioning correctly. | 2. Check gauge. Refer to Electrical - Instrument Cluster/Instrument Cluster - Diagnosis and Testing | |
| 3. Air trapped in cooling | 3. Drain cooling system and refill. Refer to Standard Procedure . | |
| 4. Radiator cap faulty. | 4. Replace radiator cap. | |
| 5. Plugged A/C or radiator cooling fins. | 5. Clean all debris away from A/C and radiator cooling fins. | |
| 6. Coolant mixture incorrect. | 6. Drain cooling system refill with correct mixture. Refer to Standard Procedure . | |
| 7. Thermostat stuck shut. | 7. Replace thermostat. | |
| 8. Bug screen or winter front being used. | 8. Remove bug screen or winter front. | |
| 9. Cylinder head gasket leaking. | 9. Check for leaking head gaskets. See Diagnosis and Testing . | |
| 10. Heater core leaking. | 10. Replace heater core. | |
| 11. cooling system hoses leaking. | 11. Tighten clamps or Replace hoses. | |
| 12. Brakes dragging. | 12. Check brakes. Refer to Brakes/Hydraulic/Mechanical - Specifications . | |
| TEMPERATURE GAUGE READING INCONSISTENT (ERRATIC, CYCLES OR FLUCTUATES) | 1. Heavy duty cooling system, extreme cold ambient (outside) temperature or heater blower motor in high position. | 1. None. System operating normally. |
| 2. Temperature gauge or gauge sensor defective. | 2. Check gauge. Refer to Electrical - Instrument Cluster/Instrument Cluster - Diagnosis and Testing | |
| 3. Temporary heavy usage or load. | 3. None. Normal condition. | |
| 4. Air trapped in cooling system. | 4. Fill cooling system. Refer to Standard Procedure . | |
| 5. Water pump | 5. Replace water pump. | |
| 6. Air leak on suction side of water pump. | 6. Check for leak. See Diagnosis and Testing | |
| RADIATOR CAP LEAKING STEAM AND / OR COOLANT INTO RESERVOIR BOTTLE. (TEMPERATURE GAUGE MAY READ HIGH) | 1. Radiator cap defective. | 1. Replace radiator cap. |
| 2. Radiator neck surface damaged. | 2. Replace radiator. | |
| HOSE OR HOSES COLLAPSE WHEN ENGINE IS COOLING. | 1. Vacuum created in cooling system on engine cool-down is not being relieved through coolant reservoir/overflow system. | 1. Replace radiator cap, check vent hose between radiator and reservoir bottle for blockage also check reservoir bottle vent for blockage. |
| NOISY FAN | 1. Fan blade(s) loose, damaged. | 1. Replace fan blade assembly. |
| 2. Thermal viscous fan drive. | 2. None. Normal condition. | |
| 3. Fan blades striking surrounding objects. | 3. Locate contact point and repair as necessary. | |
| 4. Obstructed air flow through radiator. | 4. Remove obstruction. | |
| INADEQUATE AIR CONDITIONER PERFORMANCE (COOLING SYSTEM SUSPECTED) | 1. Radiator and/or A/C condenser air flow obstructed. | 1. Remove obstruction and/or clean. |
| 2. Air seals around radiator damaged or missing. | 2. Inspect air seals, repair or replace as necessary. | |
| INADEQUATE HEATER PERFORMANCE. GAUGE MAY OR MAY NOT READ LOW. | 1. Heavy duty cooling system, and cooler ambient temperatures. | 1. None. Normal condition. |
| 2. Obstruction in heater hoses. | 2. Remove hoses, remove obstruction. | |
| 3. Water pump damaged. | 3. Replace water pump. | |
| HEAT ODOR | 1. Damaged or missing drive line heat shields. | 1. Repair or replace damaged or missing heat shields. |
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