RAM 3500 Truck 2WD L6-5.9L DSL Turbo VIN 6 (1999)
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-Typical
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.