Pinpoint Test A: The Parking Brake Will Not Apply

Parking Brake

Pinpoint Tests

Pinpoint Test A: The Parking Brake Will Not Apply

Normal Operation

When the parking brake control is pulled, the parking brake equalizer pulls on both rear parking brake cables, which are attached to the parking brake actuators and apply the brake shoes.

This pinpoint test is intended to diagnose the following:
- Parking brake cables and conduits
- Parking brake control
- Parking brake equalizer
- Rear brake hardware
- Rear brake shoes


PINPOINT TEST A: THE PARKING BRAKE WILL NOT APPLY

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A1 CHECK THE PARKING BRAKE CONTROL FOR CORRECT OPERATION


- Pull the parking brake control handle.
- Does the parking brake control move?

Yes
GO to A2.

No
GO to A4.

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A2 CHECK FOR BROKEN CABLES AND HARDWARE


- NOTE: Have an assistant pull and release the parking brake handle to help isolate disconnected cables or cables that do not move.
- Inspect the following items for damage and correct connections:
- Parking brake control
- Parking brake equalizer
- LH rear cable
- RH rear cable
- 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
GO to A3.

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A3 CHECK THE PARKING BRAKE SHOES AND HARDWARE


- Remove the rear brake drum. Refer to Drum Brake Service and Repair. Inspect the brake shoes and hardware for damage and/or missing components.
- Is any damage found or are any components missing?

Yes
INSTALL new components as necessary. TEST the system for normal operation.

No
VERIFY that the rear brake shoes and linings are within thickness specifications. REFER to Specifications in Brake System - General Information Specifications. INSTALL new brake shoes as necessary. REFER to Drum Brake Service and Repair. TEST the system for normal operation.

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A4 ISOLATE THE PARKING BRAKE CONTROL AND FRONT PARKING BRAKE CABLE


- Disconnect the rear cables from the cable equalizer.
- Pull the parking brake control handle.
- Does the parking brake control move?

Yes
GO to A5.

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

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A5 ISOLATE THE REAR PARKING BRAKE CABLES


- Remove the rear brake drum. Refer to Drum Brake Service and Repair.
- Disconnect the parking brake cables from the brake shoe actuators.
- While holding the rear cable conduit, attempt to slide the rear cable inside the conduit.
- Does the rear cable slide freely inside the conduit?

Yes
The system is operating normally at this time. The concern may have been cause by a seized or binding component. CLEAN and LUBRICATE the brake backing plate using the specified materials. CONNECT all cables and INSTALL all components. TEST the system for normal operation.

No
INSTALL new rear brake cable(s). REFER to Parking Brake Cable Service and Repair. TEST the system for normal operation.

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