Located between car engine and radiator, a car thermostat acts as a temperature controlled engine cooling valve designed to keep your engine operating at a safe regular temperature.
Car thermostats help to keep the engine warm, as well as regulating the coolant to keep the temperature down.
By allowing the engine to both warm safely and cool efficiently, the thermostat serves to reduce engine wear, deposits and emissions. The secret of the thermostat lies in the small cylinder located on the engine-side of the device. This cylinder is filled with a wax that begins to melt at around 180 F (different thermostats open at different temperatures, but 180 F is a common one). A rod connected to the valve presses into this wax. When the wax melts it expands significantly, pushing the rod out of the cylinder & opening the valve.