Radiator Cap: Testing and Inspection

DIAGNOSIS AND 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).

Operate the tester pump and observe the gauge pointer at its highest point. The cap release pressure should be 110 to 138 kPa (16 - 20 psi). The cap is satisfactory when the pressure holds steady. It is also good if it holds pressure within the 110 - 138 kPa (16 - 20 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.