Engine coolant temperature is controlled by a thermostat in the engine coolant inlet on the engine. The thermostat stops the flow of coolant through the radiator until the coolant reaches a preset temperature.

Thermostat in your vehicle engine is not a normal maintenance item. However, should your thermostat need replacing, we recommend replacement with a Saturn thermostat.

If the thermostat is thought to affect heater performance, refer to "Heater" in the Comfort Controls and Audio System section in this book before replacing the thermostat.