2014 Jeep Wrangler JK Factory Service Manual 05 - Brakes, Base

CALIPER, Disc Brake

DESCRIPTION

The calipers are a single piston type. The calipers are free to slide laterally, this allows continuous compensation for lining wear.

OPERATION

When the brakes are applied fluid pressure is exerted against the caliper piston. The fluid pressure is exerted equally and in all directions. This means pressure exerted against the caliper piston and within the caliper bore will be equal .


Fluid pressure applied to the piston is transmitted directly to the inboard brake shoe. This forces the shoe lining against the inner surface of the disc brake rotor. At the same time, fluid pressure within the piston bore forces the caliper to slide inward on the mounting bolts. This action brings the outboard brake shoe lining into contact with the outer surface of the disc brake rotor.

In summary, fluid pressure acting simultaneously on both piston and caliper, produces a strong clamping action. When sufficient force is applied, friction will attempt to stop the rotors from turning and bring the vehicle to a stop.

Application and release of the brake pedal generates only a very slight movement of the caliper and piston. Upon release of the pedal, the caliper and piston return to a rest position. The brake shoes do not retract an appreciable distance from the rotor. In fact, clearance is usually at, or close to zero. The reasons for this are to keep road debris from getting between the rotor and lining and in wiping the rotor surface clear each revolution.

The caliper piston seal controls the amount of piston extension needed to compensate for normal lining wear.

During brake application, the seal is deflected outward by fluid pressure and piston movement . When the brakes (and fluid pressure) are released, the seal relaxes and retracts the piston.

The amount of piston retraction is determined by the amount of seal deflection. Generally the amount is just enough to maintain contact between the piston and inboard brake shoe.


FRONT

  1. Install prop rod on the brake pedal to keep pressure on the brake system, Holding pedal in this position will isolate master cylinder from hydraulic brake system and will not allow brake fluid to drain out of brake fluid reservoir while brake lines are open. This will allow you to bleed out the area of repair instead of the entire system.

    2.  
  2. Raise and support vehicle.

    3.  
  3. Remove front wheel and tire assembly.

    4.  
  4. Drain small amount of fluid from master cylinder brake reservoir with clean suction gun.

    5.  
  5. Bottom caliper pistons into the caliper (4) by prying the caliper over.

    6.  
  6. Remove brake hose banjo bolt and gasket washers (1). Discard gasket washers.

    7.  
  7. Remove the caliper slide bolts (3).

    8.  
  8. Remove the caliper (4) from the adapter.

    9.  

REAR

  1. Install prop rod on the brake pedal to keep pressure on the brake system, Holding pedal in this position will isolate master cylinder from hydraulic brake system and will not allow brake fluid to drain out of brake fluid reservoir while brake lines are open. This will allow you to bleed out the area of repair instead of the entire system.

    2.  
  2. Raise and support vehicle.

    3.  
  3. Remove rear wheel and tire assembly.

    4.  
  4. Drain small amount of fluid from master cylinder brake reservoir with a clean suction gun.

    5.  
  5. Bottom caliper pistons into the caliper by prying the caliper over.

    6.  
  6. Remove brake hose banjo bolt (3) and discard gasket washers.

    7.  
  7. Remove the caliper slide pins (2).

    8.  
  8. Remove caliper from the adapter.

    9.  
  9. Remove the brake pads.

    10.  

DISASSEMBLY

  1. Remove brake shoes from caliper.

    2.  
  2. Drain brake fluid out of caliper.

    3.  
  3. Take a piece of wood and pad it with one-inch thickness of shop towels. Place this piece in the outboard shoe side of the caliper in front of the piston. This will cushion and protect caliper piston during removal.

    4.  
  4. Remove caliper piston with short bursts of low pressure compressed air. Direct air through fluid inlet port and ease piston out of bore.

    CAUTION:

    Do not blow the piston out of the bore with sustained air pressure. This could result in a cracked piston. Use only enough air pressure to ease the piston out.

    WARNING:

    NEVER ATTEMPT TO CATCH THE PISTON AS IT LEAVES THE BORE. THIS MAY RESULT IN PERSONAL INJURY.



    5.  
  5. Remove caliper piston dust boot with suitable pry tool.

    6.  
  6. Remove caliper piston seal with wood or plastic tool. Do not use metal tools as they will scratch piston bore.

    7.  
  7. Remove caliper mounting bolt bushings and boots.

    8.  

CLEANING

Clean the caliper components with clean brake fluid or brake clean only. Wipe the caliper and piston dry with lint free towels or use low pressure compressed air.

CAUTION:

Do not use gasoline, kerosene, paint thinner, or similar solvents. These products may leave a residue that could damage the piston and seal.

INSPECTION

The piston is made from a phenolic resin (plastic material) and should be smooth and clean.

The piston must be replaced if cracked or scored. Do not attempt to restore a scored piston surface by sanding or polishing.

CAUTION:

If the caliper piston is replaced, install the same type of piston in the caliper. Never interchange phenolic resin and steel caliper pistons. The pistons, seals, seal grooves, caliper bore and piston tolerances are different.

The bore can be lightly polished with a brake hone to remove very minor surface imperfections. The caliper should be replaced if the bore is severely corroded, rusted, scored, or if polishing would increase bore diameter more than 0.025 mm (0.001 inch).


ASSEMBLY

Special Tools: Click to display a list of tools used in this procedure

CAUTION:

Dirt, oil, and solvents can damage caliper seals. Insure assembly area is clean and dry.

  1. Lubricate caliper piston bore, new piston seal and piston with clean brake fluid.

    2.  
  2. Lubricate caliper bushings and interior of bushing boots with silicone grease.

    3.  
  3. Install bushing boots in caliper, then insert bushing into boot and push bushing into place.

    4.  
  4. Install new piston seal into seal groove with finger.

    5.  
  5. Install new dust boot on caliper piston and seat boot in piston groove.

    6.  
  6. Press piston into caliper bore by hand, use a turn and push motion to work piston into seal.

    7.  
  7. Press caliper piston to bottom of bore.

    8.  
  8. Seat dust boot in caliper with Installer Tool C-4842 and Tool Handle C-4171 .

    9.  
  9. Replace caliper bleed screw if removed.

    10.  

FRONT

  1. Install the caliper (4) on the adapter.

    2.  
  2. Caliper slide pins should be free from debris and lightly lubricated.

    3.  
  3. Install the caliper slide pin bolts (3) and tighten to 35 N·m (26 ft. lbs.).

    4.  
  4. Gently lift one end of the slide pin boot to equalize air pressure, then release the boot and verify that the boot is fully covering the slide pin.

    CAUTION:

    Verify brake hose is not twisted or kinked before tightening banjo bolt.


    5.  
  5. Install brake hose (1) to caliper (4) with new copper washers (6) and tighten banjo bolt (6) to 31 N·m (23 ft. lbs.).

    6.  
  6. Verify brake fluid level.

    7.  
  7. Remove the prop rod from the brake pedal.

    8.  
  8. Bleed the area of repair for the brake system, If a proper pedal is not felt during bleeding an area of repair then a base bleed system must be performed. (Refer to 05 - Brakes - Standard Procedure) .

    9.  
  9. Install wheel and tire assemblies.

    10.  
  10. Remove supports and lower vehicle.

    11.  

REAR

  1. Install the brake pads if removed.

    2.  
  2. Install caliper to the caliper adapter.

    3.  
  3. Coat the caliper mounting slide pin bolts (1) with silicone grease. Then install and tighten the bolts to 35 N·m (26 in. lbs.).

    4.  
  4. Install the brake hose banjo bolt if removed.

    5.  
  5. Install the brake hose to the caliper with new seal washers and tighten fitting bolt to 31 N·m (23 ft. lbs.).

    CAUTION:

    Verify that the brake hose is not twisted or kinked before tightening the fitting bolt.


    6.  
  6. Remove the prop rod from the brake pedal.

    7.  
  7. Bleed the area of repair for the brake system, If a proper pedal is not felt during bleeding an area of repair then a base bleed system must be performed. (Refer to 05 - Brakes - Standard Procedure) .

    8.  
  8. Install the wheel and tire assemblies (Refer to 22 - Tires and Wheels/Wheels - Standard Procedure) .

    9.  
  9. Remove the supports and lower the vehicle.

    10.  
  10. Verify a firm pedal before moving the vehicle.

    11.