Pinpoint Test B: The Parking Brake Does Not Release

Parking Brake


Pinpoint Tests

Pinpoint Test B: The Parking Brake Does Not Release

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 cable conduits, cable springs and parking brake shoe springs provide the force necessary to return the parking brake system to the released position.

This pinpoint test is intended to diagnose the following:
- Parking brake cable(s)
- Parking brake control
- Parking brake control release handle
- Parking brake shoe actuators
- Parking brake shoes and hardware



PINPOINT TEST B: THE PARKING BRAKE DOES NOT RELEASE

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B1 CHECK THE PARKING BRAKE CONTROL RELEASE HANDLE AND CABLE


- Verify that the release handle and cable are connected to the parking brake control.
- Are the release handle and cable connected?

Yes
GO to B2.

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

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B2 CHECK THE REAR PARKING BRAKE CABLES


- Disconnect the LH cable from the RH conduit equalizer.
- Disconnect the front parking brake cable from the RH rear parking brake cable at the cable union.




- Disconnect the rear parking brake cables from the parking brake actuating levers.
- 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 new rear brake cable(s). REFER to Parking Brake Cable - LH Parking Brake Cable - LH or Parking Brake Cable - RH Parking Brake Cable - RH. TEST the system for normal operation.

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B3 CHECK THE REAR PARKING BRAKE SHOES AND HARDWARE


- Remove the rear 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. REFER to Parking Brake Shoes Service and Repair. TEST the system for normal operation.

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B4 ISOLATE THE FRONT PARKING BRAKE CABLE


- NOTE: The parking brake control take-up spool tab may need to be bent aside to allow the cable to be removed.
- Disconnect the front parking brake cable and conduit from the parking brake control.




- While holding the cable conduit, attempt to slide the cable inside the conduit.
- Does the cable slide freely inside the conduit?

Yes
INSTALL a new parking brake control. REFER to Parking Brake Control Service and Repair. TEST the system for normal operation.

No
INSTALL a new front cable. TEST the system for normal operation.

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