This thermostat regulates coolant flow to maintain the engine's operating temperature within the designed range. It is installed in the housing on the coolant pump, where it opens and closes in response to coolant temperature, directing flow to the radiator or bypassing it for faster warm-up. A stuck-open thermostat causes slow warm-up and reduced heater performance; a stuck-closed unit leads to overheating. The original manufacturer's component matches the thermal response curve specified for the engine, ensuring the opening temperature and lift height are correct for the cooling system's flow demands. When replacing, clean the housing sealing surface and use a new gasket.