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Thermostat Test Procedure Using Tempil Sticks

WARNING: This page is about a different car, the 2003 GMC Safari and 2003 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.

The coolant thermostat can be tested using a temperature, or tempil stick. The tempil stick is a pencil-like device. The tempil stick 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 J 24731  Tempil Stick in order to find the opening and the closing temperatures of the coolant thermostat.
    • J 24731-188 tempil stick melts at 87°C (188°F). The thermostat should begin to open.
    • J 24731-206 tempil stick melts at 97°C (206°F). The thermostat should be fully open.
  2. Replace the coolant thermostat if the thermostat does not operate properly between this temperature range.
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