How Does The Radiator Pressure Cap Work?
The pressure cap is similar to the safety valve found on a kitchen pressure cooker. The pressure cap seals the operating cooling system forcing the hot pressurized coolant to carry approximately 50 more degrees of heat than the normal (212) boiling point of water. When seepage or leaks have reduced the quantity of coolant, the temperature rises, forcing open the pressure valve, causing even more coolant to escape. The pressure valve also operates under normal conditions. When the cooling system pressure exceeds the rated pressure of the cap, the hot coolant escapes and overflows under the pressure valve and bottom seal of the cap and into the coolant reservoir tank. After the engine is shut down and begins to cool, the temperature, and therefore the pressure, drops to a point of slight partial vacuum equal to the task of siphoning the overflow coolant back from the reservoir tank, through the vacuum valve of the radiator cap, thereby continually maintaining the radiator at full capacit
