Thermostat Diagnosis (Off-Vehicle)
THERMOSTAT INSPECTION AND TESTINGDo an operational test of the thermostat using the following procedure:
1. Drain the coolant to a level just below the thermostat.
2. Remove the coolant outlet.
3. Remove the thermostat.
4. Unless the thermostat is obviously faulty, test the thermostat before replacing the thermostat using the following procedure:
4.1. Place the thermostat and a thermometer in a container with a 50/50 solution of water and ethylene glycol antifreeze.
4.2. Place the container over a heater.
IMPORTANT: While heating, do not rest the thermostat or the thermometer on the bottom of the container. This causes the thermostat and the thermometer to be at a higher temperature than the solution.
4.3. Agitate the solution in order to maintain a uniform temperature of the solution, the thermostat, and the thermometer.
The thermostat valve should start to open at the rated temperature. The thermostat should be fully open after the temperature has increased 150° C (270° F).
A used thermostat can be about 60C (100F) above or below these settings without adversely affecting the thermostat and you do not need to replace the thermostat. If the thermostat does not operate at the temperatures specified, replace the thermostat. You cannot adjust the thermostat.