For 1990-2009 cars

1. Remove the thermostat from the vehicle in order to perform the thermostat test. Refer to Engine Coolant Thermostat Replacement .
2. Fill a pan with a 50/50 mixture of ethylene glycol and water.

Suspend the thermostat (1) and a thermometer (3) in the pan.

Do not place the thermostat (or thermometer) on the bottom of the pan. The concentration of heat is uneven at the bottom of the pan. This condition may cause inaccurate temperature measurements.

3. Place the pan on a burner (2).
4. Heat the solution.
5. Use a thermometer (3) in order to measure the temperature of the solution.
6. Ensure that the following specifications exist:

• | The thermostat valve opening temperature is within 80°C to 84°C (176°F to 183°F).

• | The valve lift is 8 mm (0.31 in) or more at 95°C (203°F).

• | If the above specifications are not met, replace the thermostat (1).

7. Verify that the valve spring is tight when the thermostat is fully closed.

Replace the thermostat if the spring is not tight.