DEFINITION: Engine temperature lamp comes ON and stays ON, or the temperature gauge shows hot, or coolant overflows from the reservoir onto the ground while the engine is running.

Check for a loss of coolant. Refer to Loss of Coolant .

Is there a loss of coolant?

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Go to Step 2

1. Check for weak engine coolant solution.
2. Do a concentration test. Refer to Coolant Concentration Testing .

Does the engine still overheat?

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Go to Step 3

System OK

1. Check for obstructed radiator air flow or bent radiator fins.
2. If necessary, remove or relocate added-on parts that block air to the radiator. Clean away any bugs, leaves, or other debris.

Does the engine still overheat?

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Go to Step 4

System OK

1. Check for a loss of system pressure.
2. Do a radiator fill cap pressure test. Refer to Thermostat Diagnosis .

Does the engine still overheat?

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Go to Step 5

System OK

1. Check for a faulty Engine Coolant Temperature (ECT) sensor. Refer to Section 8A.
2. If necessary, replace the sensor.

Does the engine still overheat?

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Go to Step 6

System OK

1. Check for a damaged coolant recovery reservoir.
2. Check for a leaking or kinked reservoir hose.
3. If necessary, reroute the reservoir hose or replace the recovery reservoir. Refer to Coolant Recovery Reservoir Replacement .

Does the engine still overheat?

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Go to Step 7

System OK

1. Check for a loose accessory drive belt.
2. Check the tension of the drive belt. Refer to Drive Belt Replacement in Engine Mechanical.

Does the engine still overheat?

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Go to Step 8

System OK

1. Check for advanced or retarded ignition timing.
2. If necessary, adjust the timing. Refer to Drive Belt Replacement in Engine Mechanical.

Does the engine still overheat?

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Go to Step 9

System OK

1. Check for blocked cooling system passages.
2. Flush the cooling system. Refer to Flushing .
3. If necessary, remove and inspect the cylinder head.

Does the engine still overheat?

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Go to Step 10

System OK

1. Check for an incorrect or damaged cooling fan blade(s).
2. Check for the correct fan blade(s) part number.
3. If necessary, replace the fan blade(s). Refer to Electric Cooling Fan .

Does the engine still overheat?

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Go to Step 11

System OK

1. Check for inoperative cooling fans. Refer to Section 8A.
2. If necessary, replace the cooling fan and motor. Refer to Electric Cooling Fan .

Does the engine still overheat?

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Go to Step 12

System OK

1. Check for a stuck closed thermostat. Refer to Engine Overheating .
2. If necessary, replace the thermostat. Refer to Engine Coolant Thermostat Replacement .

Does the engine still overheat?

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Go to Step 13

System OK

1. Check for a faulty water pump.
2. If necessary, replace the water pump. Refer to Water Pump Replacement .

Does the engine still overheat?

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Go to Step 14

System OK

1. Check for a damaged water pump Driveshaft 5.7L (VIN P).
2. If necessary, replace the water pump Driveshaft. Refer to Section a or replace the water pump. Refer to Water Pump Replacement .

Is the engine still overheating?

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Go to Step 15

System OK

1. Check the radiator cooling capacity. Refer to Section B.A.
2. Check if the radiator is the proper size for the vehicle.
3. If necessary, determine the proper radiator size and replace the radiator. Refer to Radiator Replacement .

Is the repair complete?

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System OK

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1. Allow the engine to cool.
2. Check for the proper coolant level.
3. START the engine.
4. Monitor the engine coolant temperature using the tech 1 .

Important: The coolant flow may be interrupted at times because of the thermostat closing during engine warm-up.

5. Squeeze the radiator outlet hose by hand in order to check the coolant flow while monitoring the engine coolant temperature.

Is the coolant flow through the radiator at or below 100°C (212°F)?

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Go to Step 2

Go to step 3

The problem is caused from something other than a faulty thermostat. Refer to Engine Overheating .

Is the repair complete?

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System OK

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1. Install a new engine coolant thermostat. Refer to Engine Coolant Thermostat Replacement .
2. Recheck the cooling system, using the tech 1 , to be sure the system is OK.

Is the repair complete?

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System OK

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