Pinpoint Test A: The Parking Brake Does Not Apply

Parking Brake

Pinpoint Tests

Pinpoint Test A: The Parking Brake Does Not Apply

Normal Operation

When the parking brake control is applied, tension is applied to the front parking brake cable. This tension is applied to both rear cables through the equalizer. The tension in the rear cables pulls on the parking brake shoe actuators and applies the parking brakes.

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



PINPOINT TEST A: THE PARKING BRAKE DOES NOT APPLY

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A1 CHECK THE PARKING BRAKE CONTROL


- Press the parking brake control pedal.
- Does the parking brake control move?

Yes
GO to A2.

No
GO to A3.

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A2 CHECK FOR BROKEN CABLES


- Remove the rear brake disc.
- NOTE: Have an assistant press and release the parking brake pedal to help isolate disconnected cables or cables that do not move.
- Inspect the following items for damage and correct connections:
- Cable equalizer
- Front cable
- LH rear cable and return spring
- Parking brake control
- Parking brake shoe actuators
- RH rear cable and return spring
- Is any damage found or are any components disconnected?

Yes
CONNECT the component(s) or INSTALL new parking brake component(s) as necessary. TEST the system for normal operation.

No
INSTALL new parking brake shoes. REFER to Parking Brake Shoes Service and Repair. TEST the system for normal operation.

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A3 ISOLATE THE PARKING BRAKE CONTROL AND FRONT PARKING BRAKE CABLE


- Disconnect the return spring from the equalizer.
- Relieve the tension in the parking brake cable by loosening the equalizer adjustment nut until the rear cables can be disconnected from the equalizer.
- Disconnect both rear cables from the equalizer.
- Press the parking brake control pedal.
- Does the parking brake control pedal move?

Yes
GO to A4.

No
GO to A6.

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A4 ISOLATE THE REAR PARKING BRAKE CABLES


- Remove the rear parking brake cable-to-support plate bolts and disconnect the rear parking brake cables from their actuators.
- To install, tighten the bolts to 23 Nm (17 lb-ft).
- While holding the cable conduit, attempt to slide the LH and the RH cables inside their conduits.
- Do the cables slide freely inside their conduits?

Yes
GO to A5.

No
INSTALL new rear brake cable(s). REFER to Parking Brake Cable - Rear, LH Parking Brake Cable - Rear, LH and/or Parking Brake Cable - Rear, RH Parking Brake Cable - Rear, RH. TEST the system for normal operation.

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A5 ISOLATE THE PARKING BRAKE SHOE ACTUATORS


- Remove the LH and RH parking brake shoes. Refer to Parking Brake Shoes Service and Repair.
- Attempt to move the LH and RH parking brake shoe actuators by hand.
- Do the actuators move?

Yes
INSTALL new parking brake shoes. REFER to Parking Brake Shoes Service and Repair. TEST the system for normal operation.

No
INSTALL new parking brake shoe actuator(s). TEST the system for normal operation.

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A6 ISOLATE THE FRONT PARKING BRAKE CABLE


- Remove the parking brake control adjustment nut and remove the front parking brake cable from the parking brake control.
- Attempt to slide the front parking brake 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 parking brake cable. REFER to Parking Brake Cable - Front Parking Brake Cable - Front. TEST the system for normal operation.

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