For 1990-2009 cars

The engine coolant thermostat is located at the front of the engine block. A pellet-type thermostat in the engine coolant outlet passage performs the following functions:

1. Engine coolant flow control
2. Provides fast engine warm-up
3. Regulates engine temperatures

A wax pellet element in the thermostat expands when heated and contracts when closed. The pellet element is connected through a piston to a valve and a plate. The valve remains closed and a bypass passage remains open while the engine coolant is cold, allowing full circulation of the engine coolant through the engine, the throttle body heater, and the heater core. As the engine warms, the pellet element expands, the thermostat valve opens, and the plate closes the bypass passage, permitting full engine coolant flow throughout all components of the cooling system.