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 pedal is pressed, the pedal should move a short distance, with more pressure needed to apply the pedal as it gets closer to the floor, until the parking brake shoes are fully applied. When the pedal is pressed, tension is applied to the front parking brake cable. This tension pulls on the LH rear parking brake cable, which is attached to the LH rear parking brake shoe actuator and applies the LH rear brake shoes. At the same time, the tension in the LH rear cable causes the LH rear cable conduit to attempt to straighten out. This straightening effect causes the LH rear cable conduit to pull on the RH rear parking brake cable, which is attached to the RH rear parking brake shoe actuator and applies the RH rear brake shoes.
This pinpoint test is intended to diagnose the following:
- Rear parking brake cables and conduits
- Front parking brake cable and conduit
- Parking brake shoes and hardware
- Parking brake control
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 pedal move?
Yes
GO to A2.
No
GO to A5.
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A2 CHECK FOR BROKEN CABLES
- 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.
- Front cable and conduit
- LH rear cable and conduit
- RH rear cable and conduit
- Rear cable brackets
- Are the cables in good condition?
Yes
GO to A3
No
CONNECT the cable(s) or INSTALL new parking brake component(s) as necessary. TEST the system for normal operation.
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A3 CHECK THE PARKING BRAKE SHOES, ACTUATOR LEVERS AND HARDWARE
- Remove the rear brake disc, refer to Rear Disc Brake Removal and Replacement. Inspect the parking brake shoes, actuator levers and hardware.
- Are the parking brake shoes, actuator levers and hardware in good condition?
Yes
GO to A4.
No
INSTALL new components as necessary. REFER to Parking Brake Shoes Service and Repair. TEST the system for normal operation.
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A4 CHECK THE PARKING BRAKE SHOE ADJUSTMENT
- Check the parking brake shoe adjustment. Refer to Parking Brake Shoe Adjustment Adjustments.
- Are the parking brake shoes adjusted to specification?
Yes
INSTALL a new parking brake control. REFER to Parking Brake Control Service and Repair. TEST the system for normal operation.
No
ADJUST the rear parking brake shoes. REFER to Parking Brake Shoe Adjustment Adjustments.
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A5 ISOLATE THE PARKING BRAKE CONTROL AND FRONT PARKING BRAKE CABLE
- Disconnect the front parking brake cable from the LH rear parking brake cable at the cable union.
- Press the parking brake control pedal.
- Does the parking brake control pedal move?
Yes
GO to A6.
No
GO to A7.
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A6 ISOLATE THE REAR PARKING BRAKE CABLES
- Release the rear parking brake cables from the bracket assembly.
- Release the rear parking brake cables from the parking brake actuating levers.
- While holding the cable conduit, attempt to slide the cable inside the conduit.
- Does the cable slide freely inside the conduit?
Yes
INSPECT the parking brake shoes, hardware and backing plate. INSTALL new components as necessary. REFER to Parking Brake Shoes Service and Repair. TEST the system for normal operation.
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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A7 ISOLATE THE FRONT PARKING BRAKE CABLE
- 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 parking brake cable. REFER to Parking Brake Cable - Front Parking Brake Cable - Front. TEST the system for normal operation.
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