Cooling System Pressure Cap

DESCRIPTION
All radiators are equipped with a pressure cap. This cap releases pressure at some point within a range of 83 - 110 kPa (12 - 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 that opens when system pressure reaches release range of 83 - 110 kPa (12 - 16 psi).
A rubber gasket seals radiator filler neck. This is done to maintain vacuum during coolant cool-down and to prevent leakage when system is under pressure.


OPERATION
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 cooldown.