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 brake shoes are fully applied. When the pedal is pressed, tension is applied to the front parking brake cable. This tension pulls on the RR parking brake cable, which is attached to the RR brake shoe actuator and applies the RR brake shoes. At the same time, the tension in the front cable causes the front cable conduit to attempt to straighten out. This straightening effect causes the front cable conduit to pull on the LR parking brake cable, which is attached to the LR brake shoe actuator and applies the LR brake shoes.
This pinpoint test is intended to diagnose the following:
- Brake shoes and hardware
- Parking brake cable(s) and conduit(s)
- Parking brake control
PINPOINT TEST A: THE PARKING BRAKE DOES NOT APPLY
-------------------------------------------------
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 A5.
-------------------------------------------------
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 front cable, both rear cables, cable equalizers and parking brake shoe or brake shoe actuators for damage and correct connections.
- Is any damaged found or are any cables disconnected?
Yes
CONNECT the cable(s) or INSTALL new parking brake component(s) as necessary. TEST the system for normal operation.
No
GO to A3.
-------------------------------------------------
A3 CHECK THE 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
GO to A4.
-------------------------------------------------
A4 CHECK THE BRAKE SHOE ADJUSTMENT
- Check the shoe adjustment. Refer to Drum Brake Adjustments.
- Are the shoes out of adjustment?
Yes
ADJUST as necessary. TEST the system for normal operation.
No
GO to A5.
-------------------------------------------------
A5 ISOLATE THE PARKING BRAKE CONTROL AND FRONT PARKING BRAKE CABLE
- Disconnect the RR cable and conduit from the body bracket, then disconnect the front cable from the connector.
- Disconnect the front parking brake cable conduit from the LR cable.
- Press the parking brake control pedal.
- Does the parking brake control move?
Yes
GO to A6.
No
GO to A7.
-------------------------------------------------
A6 ISOLATE THE REAR PARKING BRAKE CABLES
- Remove the rear brake shoes, refer to Drum Brake Service and Repair. Compress the rear parking brake cable conduit locking tabs and pull the cable assembly through the brake backing plate.
- While holding the cable conduit, attempt to slide the cable inside the conduit.
- Does the cable slide freely inside the conduit?
Yes
INSPECT the brake shoes, hardware and backing plate. INSTALL new components as necessary. TEST the system for normal operation.
No
INSTALL new rear brake cable(s). REFER to Parking Brake Cable - Rear, RH Parking Brake Cable - Rear, RH or Parking Brake Cable - Rear, LH Parking Brake Cable - Rear, LH. TEST the system for normal operation.
-------------------------------------------------
A7 ISOLATE THE FRONT PARKING BRAKE CABLE
- Remove the parking brake control. Refer to Parking Brake Control Service and Repair.
- 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.
-------------------------------------------------