What Does the Thermostat Do in a Car?

December 4, 2023

A thermostat is a small but vital part of your car’s cooling system. Located between your engine and the radiator, it regulates the flow of coolant to ensure the temperature stays at a preset level for optimal vehicle operation.

If your engine overheats it can cause major damage, especially to the hoses and gaskets in the cooling system. Often this is due to a defective thermostat which prevents the proper movement of coolant. Luckily, a thermostat is a simple, yet effective device. Most thermostats are built with a small cylinder that contains a wax that melts at around 180 degrees Fahrenheit. When the melted wax starts to expand it presses a rod that opens the thermostat and allows coolant to flow into the radiator. Then, when the engine reaches its pre-set operating temperature, the thermostat closes again and your car begins to cool down.

This is an excellent explanation of what a thermostat does, but there are other things it can do as well. It can also get stuck closed or open, which could be caused by a damaged spring or debris within the device. When the thermostat is stuck open, it can’t close and your engine will never reach its preset temperature. This could also lead to the engine wearing out more quickly than it should. Stuck closed can be much more problematic as it will prevent coolant from flowing to the radiator and your engine will overheat. If this happens, it’s best to replace the thermostat as soon as possible.


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