For 1990-2009 cars

Step | Action | Yes | No
--- | --- | --- | ---
DEFINITION: Either of the following conditions indicate a probable engine overheat condition.

• | The engine temperature gage is in the red (overheat) zone and/or the engine temperature indicator is ON.

• | Hot engine coolant overflows from the coolant recovery reservoir and/or radiator cap onto the ground while the engine is running.

1 |

1. Inspect and fill the cooling system, as necessary. Refer to Cooling System Draining and Filling.
2. Inspect the cooling system for leaks, as necessary.
3. Repair the cooling system leaks, as necessary.

Has the inspection/repair been performed?

Go to Step 2

--

2 |

1. Start the engine and allow the engine to run at approximately 1,200 RPM.
2. Use the Scan Tool in order to verify the overheat condition.

Does the Scan Tool verify the engine overheat condition?

Go to Step 3

Go to Diagnostic System Check - Vehicle

3 |

1. Verify that the cooling fans are operating properly.
2. Repair the cooling fan system, as necessary.

Does the engine still overheat?

Go to Step 4

System OK

4 | Perform the following inspections:

• | Inspect the radiator and the A/C condenser cooling fins for debris or any other obstruction.

• | Inspect the drive belt system and the drive belt tensioner for proper operation in order to ensure that the coolant pump is rotating properly.

• | Inspect for loose, damaged and/or missing air deflector(s).

• | Check for a pinched or kinked cooling system hose.

• | Repair the systems as necessary.

Does the engine still overheat?

Go to Step 5

System OK

5 | Inspect the thermostat for proper operation. Refer to Thermostat Diagnosis. Is the thermostat operating properly? | Go to Step 7 | Go to Step 6
6 | Replace the thermostat. Refer to Engine Coolant Thermostat Replacement. Does the engine still overheat? | Go to Step 7 | System OK
7 | Note: Excessive coolant freeze point protection MAY cause the coolant to boil at low temperatures.

1. Inspect for the proper coolant concentration (mixture). Correct the coolant concentration as necessary.
2. Remove the radiator cap.
3. Start the engine and inspect for a constant flow of air bubbles in the engine coolant.

Is there a constant flow of air bubbles in the engine coolant?

Go to Step 8

Go to Step 9

8 | The probable cause of the engine overheat is combustion chamber gasses leaking into the cooling system. This condition is usually caused by the following:

• | A worn or damaged cylinder head gasket

• | A worn or damaged cylinder head

• | A worn and/or damaged engine block

Verify this condition by inspecting the spark plug electrodes and porcelain surrounding the spark plug electrode for signs of coolant. Replace and/or repair the engine internal component(s), as necessary, in order to repair the engine internal coolant leak.

Does the engine still overheat?

Go to Step 1

System OK

9 | The engine overheat may be caused by a cooling system blockage. Flush the cooling system. Refer to Coolant System Flushing. Does the engine still overheat? | Go to Step 10 | System OK
10 | Note: It is unlikely that the water pump is the cause of the overheat condition. If NONE of the cooling system passages are restricted, replace the coolant pump. Refer to Water Pump Replacement. Does the engine still overheat? | Go to Step 1 | System OK