Does the engine overheat, boil over or have other symptoms of poor engine cooling?

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Go to Step 3

Go to Step 2

Does the engine take too long to warm up, run cold or not put out enough heat through the HVAC system?

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Go to Step 4

System OK

1. Carefully relieve the pressure in the cooling system. Remove the radiator cap.
2. Rub a 96.6 ° C (206 ° F) temperature stick onto the outside of the thermostat housing.
3. Start the engine. Let it run at fast idle until it reaches operating temperature.
4. Watch for coolant flow in the radiator.

Is the coolant flowing when the temperature stick melts?

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System OK

Go to Step 6

1. Carefully relieve the pressure in the cooling system. Remove the radiator cap.
2. Rub a 86.6 ° C (188 ° F) temperature stick onto the outside of the thermostat housing.
3. Start the engine. Let it run at fast idle until it reaches operating temperature.
4. Watch for coolant flow in the radiator.

Is the coolant flowing before the temperature stick melts?

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Go to Step 6

System OK

Recheck the system

Is the cooling system operating normally?

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System OK

Go to Step 1

Install a new thermostat.

Is the repair complete?

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Go to Step 5

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