Toyota
Jeep Cherokee
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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
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.

    More about «Description and operation»:

    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

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