Thermostat, Engine Cooling

Thermostat Diagnosis

Thermostat Test

Tools Required
^ J24731 Tempilstick

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.
1. Use a tempilstick in order to find the opening and the closing temperatures of the coolant thermostat.
^ J24731-188 tempilstick melts at 87°C (188°F). The thermostat should begin to open.
^ J24731-206 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.