Pinpoint Test C: The Parking Brake Will Not Release Using The Automatic Parking Brake Release

Parking Brake

Pinpoint Test C: The Parking Brake Will Not Release Using the Automatic Parking Brake Release

Normal Operation

Vacuum is supplied to the vacuum switch at all times (a vacuum reservoir supplies the vacuum when the engine is not running). When the transmission selector lever is placed in DRIVE, a tab on the selector lever actuates the vacuum switch which supplies vacuum to the vacuum actuator. When vacuum is supplied to the actuator, it moves a lever that is connected to the parking brake control and releases the parking brake.

This pinpoint test is intended to diagnose the following:
- Vacuum hose(s)
- Vacuum switch
- Vacuum actuator
- Actuator lever


PINPOINT TEST C: THE PARKING BRAKE WILL NOT RELEASE USING THE AUTOMATIC PARKING BRAKE RELEASE

-------------------------------------------------
C1 CHECK THE RELEASE HANDLE OPERATION


- Pull the parking brake release handle.
- Does the parking brake release?

Yes
GO to C2.

No
GO to Pinpoint Test B. Pinpoint Test B: The Parking Brake Will Not Release and/or Parking Brake Shoe Drag

-------------------------------------------------
C2 CHECK THE VACUUM ACTUATOR LEVER


- Verify that the vacuum actuator lever is connected to the parking brake control.
- Is the actuator lever connected?

Yes
GO to C3.

No
CONNECT the actuator lever and TEST the system for normal operation.

-------------------------------------------------
C3 CHECK THE VACUUM ACTUATOR OPERATION


- Disconnect the vacuum hose from the vacuum actuator.
- Connect the special tool to the actuator and apply approximately 34 kPa (10 in Hg) of vacuum.
- Does the vacuum actuator operate?

Yes
GO to C4.

No
INSTALL a new parking brake control. REFER to Parking Brake Control Service and Repair. TEST the system for normal operation.

-------------------------------------------------
C4 CHECK FOR VACUUM AT THE VACUUM ACTUATOR


NOTE: When checking for vacuum leaks, look for cracks or holes in the hoses and connections.

- Connect a vacuum gauge to the actuator vacuum supply hose.
- Block the wheels, start the engine and run at idle speed.
- Press and hold the brake pedal.
- Select DRIVE.
- Is the vacuum approximately 34 kPa (10 in Hg)?

Yes
The system is operating correctly at this time. The concern may have been caused by a loose hose or fitting. CONNECT all hoses and fittings. TEST the system for normal operation.

No
Select PARK and INSPECT the actuator supply hose for leaks, INSTALL a new hose as necessary. If no leaks are found, GO to C5.

-------------------------------------------------
C5 CHECK FOR VACUUM AT THE VACUUM SWITCH


NOTE: The vacuum supply to the vacuum switch can be checked at the in-line hose connector below the instrument panel.

- Ignition OFF.
- Remove the cap from the in-line connector and connect the vacuum gauge.
- Start the engine and run at idle speed.
- Press and hold the brake pedal.
- Select DRIVE.
- Is the vacuum approximately 34 kPa (10 in Hg)?

Yes
INSTALL a new vacuum switch. TEST the system for normal operation.

No
REPAIR the vacuum supply. TEST the system for normal operation.

-------------------------------------------------