Jeep Cherokee

 Service Manual

Cooling system » Diagnosis and testing
Radiator cap-pressure testing

Remove cap from radiator. Be sure that sealing surfaces are clean. Moisten rubber gasket with water and install the cap on pressure tester (tool 7700 or an equivalent) (Fig. 20).

Fig. 20 Pressure Testing Radiator Pressure Cap-Typical

1 - PRESSURE CAP
2 - TYPICAL COOLING SYSTEM PRESSURE TESTER

Operate the tester pump and observe the gauge pointer at its highest point. The cap release pressure should be 83-to-110 kPa (12-to-16 psi). The cap is satisfactory when the pressure holds steady. It is also good if it holds pressure within the 83-to-110 kPa (12-to-16 psi) range for 30 seconds or more. If the pointer drops quickly, replace the cap.

CAUTION: Radiator pressure testing tools are very sensitive to small air leaks, which will not cause cooling system problems. A pressure cap that does not have a history of coolant loss should not be replaced just because it leaks slowly when tested with this tool. Add water to tool. Turn tool upside down and recheck pressure cap to confirm that cap needs replacement.

CAP INSPECTION

Visually inspect the pressure valve gasket on the cap. Replace cap if the gasket is swollen, torn or worn. Inspect the area around radiator filler neck for white deposits that indicate a leaking cap.

On-board diagnostics (OBD)

Accessory drive belt diagnosis

Preliminary checks

Radiator coolant flow check

Cooling system-testing for leaks

Viscous fan drive

Electric cooling fan

Radiator cap-to-filler neck seal-pressure relief check

Radiator cap-pressure testing

Coolant-low level aeration

Deaeration