Pinpoint Test B: The Parking Brake Will Not Release And/Or Parking Brake Shoe Drag

Parking Brake

Pinpoint Tests

Pinpoint Test B: The Parking Brake Will Not Release and/or Parking Brake Shoe Drag

Normal Operation

When the parking brake release handle is pulled, the ratchet mechanism and return spring in the parking brake control release the tension on the parking brake cables and conduits. The LH rear parking brake cable conduit and the springs on both rear cables provide the force necessary to return the parking brake shoes to their released position.

This pinpoint test is intended to diagnose the following:
- Parking brake control release handle
- Front parking brake cable and conduit
- Rear parking brake cable and conduit
- Parking brake shoes and hardware
- Parking brake control

PINPOINT TEST B: THE PARKING BRAKE WILL NOT RELEASE AND/OR PARKING BRAKE SHOE DRAG

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B1 CHECK THE PARKING BRAKE CONTROL RELEASE HANDLE


- Verify that the release handle is connected to the parking brake control.
- Is the release handle connected?

Yes
GO to B2.

No
CONNECT the handle and TEST the system for normal operation.

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B2 CHECK THE REAR PARKING BRAKE CABLES


- WARNING: Before servicing a vehicle equipped with a fire suppression system, depower the system by following the procedure in Fire Suppression System. Failure to follow the instructions may result in serious personal injury Procedures.

- With the vehicle in NEUTRAL, position it on a hoist. Refer to Jacking and Lifting Service and Repair.
- Pull the parking brake adjuster clip downward.




- Disconnect the LH rear parking brake cable and conduit from the cable adjuster.




- Disconnect the front parking brake cable from the LH rear parking brake cable.




- Disconnect both rear parking brake cables from the parking brake cable extensions at the wheel ends.
- While holding the rear cable conduit, attempt to slide the rear cable inside the conduit.
- Does the cable slide freely inside the conduit?

Yes
GO to B3.

No
INSTALL a new rear cable. REFER to Parking Brake Cable - Rear Parking Brake Cable - Rear. TEST the system for normal operation. If equipped with a fire suppression system, GO to B5.

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B3 CHECK THE REAR PARKING BRAKE SHOES AND HARDWARE


- Remove the rear brake disc, refer to Rear Disc Brake Brake Disc.
- Inspect the parking brake shoes, hardware and backing plate.
- Are the shoes, hardware and backing plate in good condition?

Yes
GO to B4.

No
INSTALL new components as necessary. TEST the system for normal operation. If equipped with a fire suppression system, GO to B5.

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B4 ISOLATE THE FRONT PARKING BRAKE CABLE


- Press the retaining tabs and remove the front parking brake conduit from the frame bracket.




- Remove the front parking brake cable bracket bolt.
- To install, tighten to 12 Nm (106 lb-in).
- Press the retaining tabs and disconnect the front parking brake conduit from the parking brake control bracket.
- Push the front parking brake conduit grommet through the body.
- Verify that the front cable conduit can slide freely on the cable.
- Does the conduit slide freely on the cable?

Yes
INSTALL a new parking brake control. REFER to Parking Brake Control Service and Repair. TEST the system for normal operation. If equipped with a fire suppression system, GO to B5.

No
INSTALL a new front cable. REFER to Parking Brake Cable - Front Parking Brake Cable - Front. TEST the system for normal operation. If equipped with a fire suppression system, GO to B5.

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B5 REPOWER THE FIRE SUPPRESSION SYSTEM


- WARNING: Before servicing a vehicle equipped with a fire suppression system, depower the system by following the procedure in Fire Suppression System. Failure to follow the instructions may result in serious personal injury Procedures.

- Verify that the fire suppression system is repowered. Refer to Fire Suppression System Procedures.
- Is the fire suppression system repowered?

Yes
Fire suppression system repowering is complete.

No
REFER to Fire Suppression System Procedures for fire suppression system depowering and repowering procedure.

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