Testing For Internal Leaks

If an internal leak is suspected in the ABS circuit, a test fixture has been developed to assist in the diagnostics. This fixture will assist in determining if there is an internal leak, and if the leak is within the hydraulic unit or the pump motor assembly. It can be used whether the pump shuts off or not.

INSTALLING THE INTERNAL LEAK TEST FIXTURE # 6685

1. With the ignition key in the OFF position, discharge the ABS system by pumping the brake pedal a minimum of 40 times.

2. Locate the high pressure hose end fitting and remove the high pressure hose tube nut from the high pressure hose hydraulic fitting.





3. Verify the shut off valve on the internal leak test fixture is OPEN and install it in line with the high pressure hose (Figure 6). Screw the male end into the hydraulic unit, then the hose into the leak test fixture. The pressure gauge should be on the high pressure hose side of the shut off switch.

4. Install MST-6163 pressure tester into the hydraulic unit.

5. Refer to the "Hydraulic Pressure Performance Test" in the Antilock Diagnostic for the diagnostic tree.