2014 Flex Workshop Manual

SECTION 206-05: Parking Brake and Actuation	2014 Flex Workshop Manual
DIAGNOSIS AND TESTING	Procedure revision date: 05/02/2013

Parking Brake

Principles of Operation

Parking Brake System

The parking brake actuator is a spring-loaded, self-adjusting, foot-operated control. When the parking brake control is pressed once, tension is applied to the front parking brake cable. Pressing the pedal a second time releases the tension. This tension pulls on the RH rear parking brake cable. At the same time, the tension in the front cable causes the RH cable conduit to attempt to straighten out, causing tension that pulls the LH rear cable. Both cables are attached to their respective rear parking brake levers, applying the rear brake calipers. These levers actuate a mechanical corkscrew device inside the caliper piston. When the parking brake cable pulls on the lever, this corkscrew device pushes the piston against the pads. Normal brake pad wear allows the caliper piston to move outward from the caliper housing. This action maintains proper park brake adjustment.

Inspection and Verification

Check the operation of the parking brake system with the vehicle on a hoist and the parking brake control fully released. Check for any damaged cables and install new components as necessary.

The first indication that something may be wrong in the parking brake system is a change in the feeling through the parking brake control. The parking brake not holding on an incline or dragging after being released are also indicators of system concerns.

Verify the customer concern.

Visually inspect for obvious signs of mechanical damage.

Visual Inspection Chart

Mechanical	Electrical
Parking brake control Front parking brake cable and conduit LH rear parking brake cable and conduit Rear brake calipers RH rear parking brake cable and conduit	Wiring, terminals or connectors Parking brake switch

If an obvious cause for an observed or reported concern is found, correct the cause (if possible) before proceeding to the next step.

If the cause is not visually evident, verify the symptom and GO to Symptom Chart .

Symptom Chart

Symptom Chart
Condition	Possible Sources	Action
The red brake warning indicator is always illuminated	Parking brake not fully released Low brake fluid level Wiring, terminals or connectors Brake master cylinder inoperative	REFER to Diagnosis and Testing in Section 413-01 to diagnose the red brake warning indicator.
The parking brake does not apply/hold vehicle	Parking brake cable(s) Parking brake control Rear brake calipers	GO to Pinpoint Test A .
The parking brake will not release	Front cable LH cable Parking brake control Rear brake calipers RH cable	GO to Pinpoint Test B .

Pinpoint Tests

Pinpoint Test A: The Parking Brake Does Not Apply/Hold Vehicle

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 is fully applied. When the parking brake control is pressed, tension is applied to the front parking brake cable. This tension pulls on the RH rear parking brake cable, which is attached to the RH rear parking brake actuator, and applies the RH rear brake caliper. At the same time, the tension in the front cable causes the RH cable conduit to attempt to straighten out. This straightening effect causes tension that pulls the LH rear cable, which is attached to the LH rear parking brake actuator, and applies the LH rear brake caliper.

This pinpoint test is intended to diagnose the following:

Front parking brake cable and conduit
Parking brake control
Rear parking brake cables and conduits
Rear brake calipers

PINPOINT TEST A: THE PARKING BRAKE DOES NOT APPLY/HOLD VEHICLE

Test Step	Result / Action to Take
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 .
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: Parking brake control Front cable LH rear cable RH rear cable Cable equalizer Rear brake caliper actuators 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 VERIFY that the rear pads and brake discs are within thickness specifications. REFER to Specifications in Section 206-00 . If the rear pads and brake discs are OK, INSTALL new rear brake calipers. REFER to Section 206-04 .
A3 ISOLATE THE PARKING BRAKE CONTROL AND FRONT PARKING BRAKE CABLE
Disconnect the front cable from the RH cable at the cable union by releasing the locking tab. Press the parking brake control pedal. Does the parking brake control pedal move?	Yes GO to A4 . No INSTALL a new parking brake control. REFER to Parking Brake Control in this section. TEST the system for normal operation.
A4 ISOLATE THE REAR PARKING BRAKE CABLES
Disconnect the LH and RH parking brake cables from the subframe brackets and the brake calipers. While holding the cable conduit, attempt to slide the cable inside the conduit. Does the cable slide freely inside the conduit?	Yes INSTALL new rear brake calipers. REFER to Section 206-04 . No INSTALL new rear brake cable(s). REFER to Parking Brake Cable — Rear in this section. TEST the system for normal operation.

Pinpoint Test B: The Parking Brake Will Not Release

Normal Operation

When the parking brake control is fully applied and the pedal is pressed a second time, the ratchet mechanism in the parking brake control releases the tension on the parking brake cables and conduits. The springs on both rear brake calipers provide the force necessary to return the brake pads and cables to their released position.

This pinpoint test is intended to diagnose the following:

Front parking brake cable and conduit
Parking brake control
Rear parking brake cable and conduit
Rear brake calipers

PINPOINT TEST B: THE PARKING BRAKE WILL NOT RELEASE

Test Step	Result / Action to Take
B1 CHECK THE PARKING BRAKE CONTROL
Press the parking brake control pedal. Does the parking brake control move?	Yes GO to B2 . No INSTALL a new parking brake control. REFER to Parking Brake Control in this section. TEST the system for normal operation.
B2 CHECK THE REAR PARKING BRAKE CABLES
Disconnect the LH and RH cables from the front cable equalizer. Disconnect the LH and RH parking brake cables from the subframe brackets and the brake calipers. While holding the rear cable conduit, attempt to slide the rear cable inside the conduit. Does the cable slide freely inside the conduit?	Yes GO to B3 . No INSTALL new rear brake cable(s). REFER to Parking Brake Cable — Rear in this section. TEST the system for normal operation.
B3 CHECK THE REAR BRAKE CALIPERS AND HARDWARE
Inspect the brake calipers, actuators and return springs. Are the components in good condition?	Yes INSTALL a new parking brake control. REFER to Parking Brake Control in this section. TEST the system for normal operation. No INSTALL new components as necessary. REFER to Section 206-04 . TEST the system for normal operation.