Parking Brake Release Motor: Testing and Inspection

Look closely at the operation of the brake linkage as the parking brake pedal is depressed. Then, check the operation of the brake linkage of when the manual release lever is activated. These checks will indicate whether the manual parking brake control linkage is operating properly or requires service or adjustment. Adjustment may be necessary if the parking brake is unable to prevent moderate vehicle movement. Perform tests of the parking brake system and controls after making sure the linkage and manual controls operate properly.

When testing a parking brake vacuum release system, a minimum of 34 kPa (10 in-Hg)should be available at all points where vacuum is applied. This can be checked with a gauge, such as Rotunda Vacuum Tester 021-00014 or equivalent.

Failure to maintain 34 kPa (10 in-Hg) during vacuum system tests could be caused by a loose hose connection, resulting in a vacuum leak. When checking for vacuum between two points, trace the hose along its entire routing to ensure it is not crossed with another hose or connected to the wrong connection.

All of the vacuum parking brake control checks are to be performed with the engine running at idle speed.

To detect any leaks in the parking brake hoses or to find disconnected or improperly connected hoses. listen for a hissing sound along the hose routing.

CAUTION: Do not apply air pressure to the vacuum system under any circumstances because the actuator diaphragm in the parking brake vacuum motor may be damaged.

1. Start engine and run it at idle speed. With the transmission shift control in NEUTRAL, depress parking brake pedal to apply parking brake. Move transmission shift control to D range, and observe the parking brake sector to see if the sector returns to its zero travel position when the parking brake releases. If parking brake releases, the parking vacuum control is working properly.

NOTE: The parking brake vacuum release does not operate with transmission in REVERSE.

2. If parking brake does not release, test for vacuum at the vacuum line connected to the parking brake release vacuum motor. This can be accomplished by removing the hose from each component and attaching it to the vacuum gauge. Vacuum will be available at the vacuum motor only when the transmission selector is in the D range. Connect two distributor tester vacuum hose adapters together with a coupling as a connector attaching the gauge. A minimum of 34 kPa (10 in.-Hg) is required to actuate the parking brake vacuum motor. If a minimum reading is not present when checking each of the above components, they must be replaced.