A thermostat that remains closed or only partially open restricts the flow of coolant in the system.

A faulty thermostat may cause the engine to overheat.

A thermostat that sticks in the full open position prevents the engine from reaching the normal operating temperature. Cold engine operation may cause a buildup of excess carbon deposits on the following components:

1. Remove the thermostat assembly.

Refer to Engine Coolant Thermostat Replacement .




2. Suspend the thermostat and a thermometer in water. Place the thermostat near the thermometer.
3. Heat the water.
4. Record the temperature at which the thermostat begins to open.
5. Record the temperature at which the thermostat is open.
6. Compare the temperature readings with the Engine Thermostats.
7. Replace the thermostat and the gasket as needed.

Refer to Engine Coolant Thermostat Replacement .

8. Fill the cooling system.
9. Run the engine until the engine reaches normal operating temperature.
10. Inspect for coolant leaks around the thermostat housing and the gasket.
11. Inspect the coolant level. Add additional coolant as necessary.
12. Install the radiator cap.