How to Determine Thermostat Failure?

[DeCorey]

Methods to determine thermostat failure are as follows: 1. Open the filler cap of the coolant reservoir and observe if there is any water flow inside. If not, it indicates that the thermostat is damaged or there is debris stuck between the main valve switch. 2. Remove the thermostat from the vehicle and place it in boiling water to observe if it opens as the water temperature rises. 3. Start the engine and after 3 minutes, feel the upper and lower radiator hoses. If the thermostat is functioning properly, the upper and lower hoses will have different temperatures—typically, the upper hose will be hot and the lower hose will be cool. The thermostat is a valve that controls the flow path of the coolant, serving as an automatic temperature-regulating device. It usually contains a temperature-sensitive component that opens or closes the flow of air, gas, or liquid through thermal expansion or contraction.