For 1990-2009 cars

Caution: With a pressurized cooling system, the coolant temperature in the radiator can be considerably higher than the boiling point of the solution at atmospheric pressure. Removal of the radiator cap, while the cooling system is hot and under pressure, causes the solution to boil instantaneously with explosive force. This will cause the solution to spew out over the engine, the fenders and the person removing the cap. Serious bodily injury may result.

A pressure vent cap is used on the radiator. The cap contains both a pressure and a vacuum relief valve. The pressure valve is held against its seat by a spring of predetermined strength, protecting the cooling system by relieving internal pressure which exceeds design specifications. System pressure is relieved when it rises 90 kPa (12.8 psi) above normal atmospheric pressure: 101 kPa (14.7 psi) at sea level. The vacuum valve is held against its seal by a light spring. This spring permits the opening of the valve in order to relieve the vacuum created in the system when it cools off. This is important because the vacuum could cause the radiator to collapse.

Do not remove the radiator cap to check the Engine Coolant Level (ECL). Check the level visually at the see-through coolant recovery reservoir. Coolant should be added only to the reservoir.