I have heard that the radiator pressure cap has four additional functions in addition to pressurizing the system. What are the other functions?
1) Filler cap to access the cooling sytem.
2) Closure cap to keep coolant in the radiator.
3) Pressure cap to prevent overheating by pressurizing the system to raise the boiling temperature of coolant and allow the automobile's engine to operate at more efficient higher temperatures.
4) Pressure relief valve to safely and harmlessly vent excess pressure into the overflow jug.
5) Vacuum relief/siphon valve to draw coolant from the overflow jug back into the radiator to prevent air from entering the system and allowing the coolant to perform its function more efficiently.
