Thermostat Diagnosis

Thermostat Diagnosis

Tools Required

J 24731 Tempil stick

The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil-like device which has a wax material containing certain chemicals that melt at a given temperature. Temperature sticks can be used to determine a thermostat's operating range by rubbing 87°C (188°F) and 97°C (206°F) sticks on the outlet coolant hose.

1. Use a tempil stick in order to find the opening and the closing temperatures of the thermostat.
J 24731 tempil stick melts at 87°C (188°F). The thermostat should begin to open at 82°C (181°F).
2. Replace the thermostat if it does not operate correctly between this temperature range.