For 1990-2009 cars

### Diagnostic Aids

The engine may overheat due to an intermittent operation of the thermostat.

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
DEFINITION: Engine temperature lamp comes ON and stays ON, or the temperature gage shows hot, or coolant overflows from the coolant recovery reservoir onto the ground while the engine is running.
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | Inspect the coolant recovery reservoir 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 | Inspect for loose, damaged, and/or missing of the following:

• | The A/C condenser seals

• | The front air deflector

• | The side seals

Repair the system as necessary.

Does the engine still overheat?

--

Go to Step 5

Go to Step 17

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 17
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 17
9 | Inspect the drive belt tensioner. Refer to Drive Belt Tensioner Diagnosis or Drive Belt Tensioner Diagnosis . 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 Drive Belt Tensioner Replacement or Drive Belt Tensioner Replacement . Does the engine still overheat? | -- | Go to Step 11 | Go to Step 17
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 17
13 | Inspect for an inoperative fan clutch. Refer to Fan Clutch Diagnosis . Does the engine still overheat? | -- | Go to Step 14 | Go to Step 17
14 | Inspect for blocked cooling system passages. Are the cooling system passages blocked? | -- | Go to Step 15 | Go to Step 16
15 | Replace the radiator. Refer to Radiator Replacement . Does the engine still overheat? | -- | Go to Step 16 | Go to Step 17
16 | Replace the engine water pump. Refer to Water Pump Replacement . Did you complete the repair? | -- | Go to Step 17 | --
17 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2