Thermostat: Testing and Inspection

Thermostat Diagnosis

For detailed thermostat diagnostic procedures. Refer to Cooling Systems; Testing and Inspection; Procedues; Diagnostic Information and Procedures.
Diagnostic Information and Procedures

Thermostat Test

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

Tools Required

- J 24731-188 188 °F Tempilstick
- J 24731-206 206 °F Tempilstick

1. Use a tempilstick in order to find the opening and the closing temperatures of the coolant thermostat.

- J 24731-188 tempistick melts at 87 °C (188 °F). The thermostat should begin to open.

- J 24731-206 tempilstick melts at 97 °C (206 °F). The thermostat should be fully open.

2. Replace the coolant thermostat if it does not operate properly between this temperature range.