Pressure Cap: Description
The cooling system is equipped with a pressure cap that releases built up pressure, maintaining a range of 97 - 124 kPa (14-18 psi).
There is also a vent valve in the center of the cap. This valve also opens when coolant is cooling and contracting, allowing coolant to return to radiator from coolant reserve/recovery system container by vacuum through connecting hose. If valve is stuck shut, the radiator hoses will be collapsed on cool down. Clean the vent valve ( Fig 1 ) to ensure proper sealing when boiling point is reached.