Thermostat Diagnosis

Thermostat Diagnosis

Thermostat Test Procedure Using Tempilsticks





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 thermostat's operating range, by rubbing 87°C (188°F) and 97°C (206°F) sticks on the thermostat housing (4).

Tools Required

J 24731 Tempilstick

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

* J 24731-188 tempilstick melts at 87°C (188°F). The thermostat should begin to open at 90°C (194°F).
* J 24731-206 tempilstick melts at 97°C (206°F). The thermostat should be fully open at 107°C (225°F).

2. Replace the coolant thermostat if it does not operate properly between this temperature range. Refer to Engine Coolant Thermostat Replacement (LH8) (Service and Repair)Engine Coolant Thermostat Replacement (with LLV and LLR) (Service and Repair).