Thermostat-Mechanical Test

Thermostat Test, Mechanical

NOTE: Fully open means the thermostat valve lifts a distance of 5.8 mm (0.2 inch) or more off the valve seat.

Remove the thermostat and immerse in a boiling antifreeze and water mixture. The thermostat should begin to open at 86 - 90°C (187 - 194°F) 2.0L engine, 84 - 88°C (183 - 190°F) 2.5L engine and be fully open at 102°C (216°F) 2.0L engine, 99°C (210°F) 2.5L engine. Install a new thermostat if it does not operate as specified.
If heat is not available, check the thermostat for leakage. Hold the thermostat up to a lighted background. Leakage of light around the thermostat valve at room temperature indicates that the thermostat should be replaced. Some thermostats have a small leakage notch at one location on the perimeter of the thermostat valve, which is considered normal.