Durango 4WD V8-5.9L VIN Z (1998)
Radiator Cap: Description and Operation
Radiators are equipped with a pressure cap, which releases pressure at some point within a range of 97 - 124 kPa (14 - 18 psi). The pressure relief point
(in pounds) is engraved on top of cap.
Radiator Pressure Cap And Filler Neck
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 that opens when system pressure reaches release range of 97 - 124 kPa
(14 - 18 psi).
A vent valve in the center of cap allows a small coolant flow through cap when coolant is below boiling temperature. The valve is completely closed
when boiling point is reached. As the coolant cools, it contracts and creates a vacuum in the cooling system. This causes the vacuum valve to open and
coolant in the reserve/overflow tank to be drawn through its connecting hose into radiator. If the vacuum valve is stuck shut, the radiator hoses will
collapse on cool down. Clean the vent valve.
A rubber gasket seals radiator filler neck to prevent leakage. This is done to keep system under pressure. It also maintains vacuum during coolant
cool-down allowing coolant to return from reserve/ overflow tank.
