Cooling system pressure cap, rated to 20lbs (psi), suitable for radiators and coolant header tanks from OBP. These traditional caps have been used for years with the range of different pressure caps often being used to adjust the pressure and therefore the boiling point of the coolant in your car's cooling system. The radiator cap pressure valve consists of a spring-loaded disc that contacts the filler neck. The spring pushes the valve into the neck to form a seal. Under pressure, the boiling point of water increases. Normally water boils at 212°F. However, for every pound of pressure increase, the boiling point goes up 3°F.
If the engine overheats and the pressure exceeds the cap rating, the pressure valve opens. Excess pressure forces coolant out of the overflow tube and into the reservoir or onto the ground. This prevents high pressure from rupturing the radiator, gaskets, seals or hoses.
Seals the top of the radiator filler neck to prevent leakage
Pressurises system to raise boiling point of coolant
Relieves excess pressure to protect against system damage
In a closed system, it allows coolant flow into and from the coolant reservoir
Always remove the radiator cap slowly and carefully. Removing the radiator cap from a hot pressurised system can cause serious burns from escaping steam and coolant.