Jeep Cherokee

 Service Manual

Cooling system » Description and operation
Radiator 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 (Fig.

9).

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 springloaded 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

Fig. 9 Radiator Pressure Cap and Filler Neck-Typical

1 - FILLER NECK SEAL
2 - VACUUM VENT VALVE
3 - PRESSURE RATING
4 - PRESSURE VALVE

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.

Cooling system

Automatic transmission oil cooler

Coolant reserve/overflow system

Cooling system fans

Block heater

Thermostat

Radiator

Radiator pressure cap

Water pump

Hose clamps

Viscous fan drive

Electric cooling fan