Cooling System Description

The Saturn cooling system uses a pressurized coolant surge tank and doesn't have a reservoir or overflow bottle. All components of the cooling system are filled from the surge tank and no additional bleeding is necessary.
At cold start-up, the thermostat will be in the closed position. The engine water pump will pump coolant through the cylinder block and head. Coolant is also pumped through the heater inlet hose to the heater core. Coolant returns from the heater core through the heater outlet hose to the engine block. Any air in the engine block or heater core is carried by coolant to the surge tank through the head degas hose. Coolant then flows from the surge tank back to the engine block through the return hose portion of the lower radiator hose.
When the coolant returns to the engine block it flows over the thermostat element. When the coolant temperature reaches 90°C (194°F) the thermostat will began to open. The coolant will flow through the upper radiator hose, through the radiator, and back to the engine through the lower radiator hose.