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 pressed, tension is applied to the intermediate parking brake cable. The intermediate cable is attached to both rear cables by an equalizer. The tension pulls equally on both rear parking brake cables, which are attached to the rear parking brake actuators and apply the parking brake shoes.
This pinpoint test is intended to diagnose the following:
- Parking brake cable(s)
- Parking brake control
- Rear brake hardware
- Rear brake shoes and linings
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
- Intermediate cable
- 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 Disc Brake System. 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 cable from the intermediate 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 A8.
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A6 ISOLATE THE INTERMEDIATE PARKING BRAKE CABLE
- Disconnect the LH and RH rear cables from the intermediate cable equalizer.
- While holding the intermediate cable conduit, attempt to slide the intermediate cable inside the conduit.
- Does the intermediate cable slide freely inside the conduit?
Yes
GO to A7.
No
INSTALL new intermediate brake cable. REFER to Parking Brake Cable - Intermediate Parking Brake Cable - Intermediate. TEST the system for normal operation.
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A7 ISOLATE THE REAR PARKING BRAKE CABLES
- Disconnect the rear 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 caused by a seized or binding component. CLEAN and LUBRICATE the parking brake backing plate. 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 - 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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A8 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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