A thermostat is an essential component of the engine's cooling system. The thermostat's function is to maintain the temperature of the coolant in the vehicle, keeping it within the normal operating range. When the thermostat is in working condition, it will open when the temperature of the engine reaches its normal range. The coolant will then circulate through the radiator, where it will cool down. When the thermostat becomes defective, it will not open properly. Checking for a bad thermostat can be done using a simple technique.
Open the hood of the vehicle and secure it in place. Make sure that the vehicle's engine is completely cool. Locate the thermostat, found underneath the radiator cap. You will see a short black hose that is attached to the thermostat. Place a container underneath the vehicle to catch the coolant from the hose.2
Loosen and remove the screws that are located on either side of the hose, then twist the hose until it becomes loose. Remove the screws from the thermostat cover, then remove the cover along with the thermostat.3
Heat one quart of water in a pot to 200 degrees Fahrenheit. Use a cooking thermometer to test the temperature of the water. Place the cooking thermometer into the water and watch the gauge, while the water starts to heat.4
Place the the thermostat gently into the pot of hot water when it reaches 200 degrees Fahrenheit. A cooking thong can be used to submerge it into the hot water to prevent splashing. If the thermostat is working correctly, it should start to open up immediately. If it still remains closed, that means that your thermostat is bad and needs to be replaced.