A pressure vent cap is used on the cross-flow radiator to allow a build-up between 93 kPa - 124 kPa (13.5 psi - 18 psi) in the cooling system. This pressure raises the boiling point of coolant to approximately 129°C (265°F) at sea level. Do not remove the radiator cap to check the engine coolant level. Check the coolant visually at the see-through coolant reservoir. Coolant should be added only to the reservoir.

Caution: As long as there is pressure in the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution to boil. Removal of the pressure cap while the engine is hot and pressure is high will cause the solution to boil instantaneously -- possibly with explosive force -- spewing the solution over the engine, fenders and the person removing the cap.

The pressure-type radiator filler cap contains a blow-off (or pressure valve) and a vacuum (or atmospheric valve). The pressure valve is held against its seat by a calibrated spring and protects the radiator by relieving any internal pressure exceeding design specification.

The radiator cap is designed to prevent accidental removal. The finger grips have been removed so that the cap is round in shape. It must be pushed downward before it can be removed. A rubber/asbestos gasket is added to the diaphragm spring at the top of the cap. Also, embossed on the cap is a caution against its being opened, and arrows indicating the proper closed position.