What Does a Car Thermostat Do?
As any other water-cooled engine on a passenger vehicle, the engine in your car operates at a temperature range of 195 and 220F (91 and 104C), approximately. To help it operate within this range, your car engine uses a thermostat. In simple terms, the thermostat responds to changes in temperature - in this case coolant temperature - by opening or closing a valve to control coolant flow between the radiator and engine. The valve itself operates through a wax-container element. Thus, the thermostat is small, simple and effective. The expanding element container in the thermostat faces and contacts the engine coolant. As the coolant temperature rises, the fluid - or wax in the container begins to melt and expand, pushing a small rod that separates a center plate from its surrounding mounting base to open the valve.
The Thermostat at Work:
The thermostat starts at a closed position when you start the engine to help it reach operating temperature. As coolant temperature rises, it begins to open. The opening allows hot coolant in the engine to flow into the radiator, while the water pump pushes lower-temperature coolant from the radiator into the engine. When the lower-temperature coolant reaches the thermostat container, the expanding fluid begins to contract, closing the thermostat's valve. During engine operation, though, the thermostat actually never fully closes or opens, but gradually nears either state to control coolant flow, depending on engine operating conditions. This allow the engine to operate at the best temperature. This ideal engine-operating temperature accomplishes several goals: It helps engine oil to lubricate efficiently and to remove harmful deposits. It reduces emissions and gas consumption, and contributes to engine performance.
Bad Car Thermostat Symptoms:
A failed thermostat will prevent the engine from operating within its ideal temperature range and affect its performance. A thermostat stuck opened will cause a continuous flow of coolant, resulting in a lower operating temperature. Since the oil operates below temperature, the condition accelerates parts' wear, reducing engine efficiency and increasing emissions over time. On the other hand, a thermostat stuck in the closed position will prevent coolant flow and cause the temperature to steadily rise. If you fail to notice and keep your engine running, in a matter of minutes your engine self-destructs. Literally. Either way, your engine will suffer damage. The difference is just in the amount of time it takes. Still, a failing thermostat is not the only cause for an abnormal engine operating temperature. Other reasons include low coolant level, a bad water pump, a worn out or loose water pump belt, cooling system leaks, a clogged radiator, a failed radiator fan and a collapsed radiator hose.