Use one of the following procedures in testing for a malfunctioning thermostat.

The coolant thermostat can be tested using a temperature indicating stick. The temperature indicating stick is a pencil-like device which has a wax material containing certain chemicals that melt at a given temperature. Temperature indicating 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 pipe.

1. Use a temperature indicating stick in order to find the opening and the closing temperatures of the thermostat.
• 188 Tempilstick® melts at 87°C (188°F). The thermostat should begin to open at 90°C (194°F).
• 206 Tempilstick® melts at 97°C (206°F). The thermostat should be fully open at 107°C (225°F).
2. Replace the thermostat if it does not operate properly between this temperature range.

Inspect the operation of the thermostat by hanging the thermostat on a hook in a 50/50 percent solution of DEX-COOL® and clean drinkable water.

In order to inspect if the thermostat valve is opening properly, perform the following test:

1. Completely submerge the thermostat in the glycol solution. The solution should be 11°C (22°F) above the temperature indicated on the thermostat valve.
2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should open.

In order to inspect if the thermostat valve is closing properly, perform the following test:

1. Completely submerge the thermostat in a glycol solution. The solution should be 6°C (10°F) below the temperature indicated on the thermostat valve.
2. Thoroughly agitate the solution. Under these conditions, the thermostat valve should close completely.