what is a thermostat on an engine
A thermostat is part of the cooling system that regulates the temperature of the coolant in the engine. The thermostat is a metal valve that has a temperature sensor built in. It can either be open or closed. When the thermostat is closed, it keeps the coolant in the engine. When the engine gets to a predetermined temperature, the thermostat opens allowing coolant to circulate. The circulation of coolant prevents the engine from overheating. If the thermostat fails to open, the car will overheat.