Thermostat Test Procedure Using Glycol

WARNING: This page is about a different car, the 2002 Buick Regal and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.

Inspect the operation of the thermostat by hanging the thermostat on a hook in a 33 percent glycol solution.

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

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

Fig 1: Inspect If The Thermostat Valve Is Opening Properly

Courtesy of GENERAL MOTORS CORP.

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

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