For 1990-2009 cars

The following actions occur when the temperature in the system rises:

1. The coolant expands.
2. The pressure valve in the radiator cap opens.
3. Coolant flows into the reservoir.
4. The system temperature drops.
5. A vacuum is created in the radiator.
6. The vacuum valve in the cap opens.
7. The vacuum pulls coolant back into the radiator from the reservoir.

The system maintains a constant engine coolant level (ECL) in the radiator. The constant level assists in cooling the engine.

Maintain the ECL between the FULL and LOW marks on the coolant reservoir. Add coolant only through the coolant reservoir. Do not add coolant directly into the radiator.