Diagnostic Aids
The engine may overheat due to an intermittent operation of one of the following components:
| • | The after boil heater pump |
| • | The coolant bypass solenoid |
| • | The coolant bypass valve |
| • | The mechanical cooling fan |
| • | The electric cooling fans |
| • | The thermostat |
For electrical inspection of the cooling fans and the after boil heater pump, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
Step | Action | Value(s) | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
DEFINITION: Engine temperature lamp comes ON and stays ON, or the temperature gage shows hot, or coolant overflows from the surge tank onto the ground while the engine is running. | ||||||||||
1 | Did you perform the Engine Cooling Diagnostic System Check? | -- | Go to Step 2 | |||||||
2 | Inspect the surge tank for low coolant. Is there a loss of coolant? | -- | Go to Loss of Coolant | Go to Step 3 | ||||||
3 |
Important: Do not allow the engine temperature to exceed the specified value. Start the engine and allow to reach normal operating temperature. Does the engine begin to exceed the specified value? | 107°C (225°F) | Go to Step 4 | Go to Diagnostic Aids | ||||||
4 |
Does the engine still overheat? | -- | Go to Step 5 | Go to Step 18 | ||||||
5 | Using the J 23688 Coolant and Battery Fluid Tester, test for insufficient coolant concentration. Is the coolant protection greater than the specified value? | -37°C (-34°F) | Go to Step 6 | Go to Step 7 | ||||||
6 | Correct the coolant concentration as necessary. Does the engine still overheat? | -- | Go to Step 7 | Go to Step 18 | ||||||
7 | Inspect for obstructed radiator air flow or bent radiator fins. Is the radiator air flow obstructed? | -- | Go to Step 8 | Go to Step 9 | ||||||
8 | Clean the radiator. Refer to Radiator Cleaning . Does the engine still overheat? | -- | Go to Step 9 | Go to Step 18 | ||||||
9 | Inspect the drive belt tensioner. Refer to Drive Belt Tensioner Diagnosis in Engine Mechanical - 3.6L or Drive Belt Tensioner Diagnosis in Engine Mechanical - 4.6L. Is the drive belt tensioner working properly and is the tension correct? | -- | Go to Step 11 | Go to Step 10 | ||||||
10 | Replace the drive belt tensioner. Refer to Water Pump and Generator Belt Tensioner Replacement or Air Conditioning Compressor and Power Steering Pump Belt Tensioner Replacement in Engine Mechanical - 3.6L or Drive Belt Tensioner Replacement - Generator or Drive Belt Tensioner Replacement - Air Conditioning, Power Steering, and Water Pump in Engine Mechanical - 4.6L. Does the engine still overheat? | -- | Go to Step 11 | Go to Step 18 | ||||||
11 | Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis . Does the thermostat operate properly? | -- | Go to Step 13 | Go to Step 12 | ||||||
12 | Replace the thermostat. Refer to Engine Coolant Thermostat Replacement . Does the engine still overheat? | -- | Go to Step 13 | Go to Step 18 | ||||||
13 | Inspect for an inoperative after boil coolant pump if equipped. Refer to After Boil Coolant Pump Inoperative . Does the engine still overheat? | -- | Go to Step 14 | Go to Step 18 | ||||||
14 | Inspect for an inoperative cooling fan. Refer to Cooling Fan Inoperative or Fan Clutch Diagnosis . Does the engine still overheat? | -- | Go to Step 15 | Go to Step 18 | ||||||
15 | Inspect for blocked cooling system passages. Are the cooling system passages blocked? | -- | Go to Step 16 | Go to Step 17 | ||||||
16 | Replace the radiator. Refer to Radiator Replacement . Does the engine still overheat? | -- | Go to Step 17 | Go to Step 18 | ||||||
17 | Replace the engine water pump. Refer to Water Pump Replacement . Did you complete the repair? | -- | Go to Step 18 | -- | ||||||
18 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2 | ||||||
