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: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot. The cooling system will release scalding fluid and steam under pressure if radiator cap or surge tank cap is removed while the engine and radiator are still hot.

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.