The thermostat allows coolant to flow through your engine, keeping it from overheating, when the engine has reached a specified temperature. If faulty, your engine may not reach operating temperature, or may overheat, which can cause coolant to leak from the vehicle, and other damage. Replace your faulty thermostat today and keep yourself from future repair. This thermostat includes the thermostat housing, as well as thermostat housing plug and plug gasket. The thermostat housing gasket is included.