The thermostat is an important part of any vehicle's cooling system as it helps regulate the engine's temperature by constantly changing the amount of coolant that flows through the engine. When the part fails, the engine receives too little coolant and overheats, or the engine receives too much coolant and becomes harder to warm up in cold weather. If the part is not changed when it fails, damage to the engine may occur due to overheating. The thermostat is one of many failure points in a cooling system, and knowing if you need a new thermostat can help pinpoint and eventually solve the issue.
Watch your engine's temperature gauge. If the gauge constantly reads near or within the red zone, chances are you need a new thermostat. This is much harder to determine if your vehicle only has a separate warning light for the engine temperature instead of an actual temperature gauge. The "Check Engine" light usually comes on only when the engine is severely overheated.
Remove the thermostat from the engine and inspect its outward appearance. Removing the thermostat will involve draining some of the coolant from your engine so have a drain pan on hand to catch the coolant. If the thermostat appears rusty or corroded, replace it with a new one.
Test the thermostat by heating up a pot of water to about 160 to 180 degrees Fahrenheit. Place the thermostat in the water and observe it. A working thermostat will open up in response to the wax pellet inside melting and expanding due to the heat. If the thermostat does not expand or if it seems stuck, have it replaced.
