Diesel Engine

Fig 1: Radiator Pressure Cap

Courtesy of CHRYSLER GROUP, LLC

All vehicles are equipped with a pressure cap. This cap releases pressure at some point within approximately 110 kPa (16 psi). The pressure relief point (in pounds) is engraved on top of the cap.

The cooling system will operate at pressures slightly above atmospheric pressure. This results in a higher coolant boiling point allowing increased radiator cooling capacity. The cap contains a spring-loaded pressure relief valve. This valve opens when system pressure reaches the release range of approximately 110 kPa (16 psi).

A rubber gasket seals the radiator filler neck. This is done to maintain vacuum during coolant cool-down and to prevent leakage when system is under pressure.