Overhaul

Fig. 7 Rear disc brake caliper assembly (Typical):

Fig. 7 Rear Disc Brake Caliper Disassembling:

DISASSEMBLE
1. Remove caliper assembly as described previously.
2. Remove caliper end retainer, operating shaft, thrust bearing and balls, Fig. 7.
3. Remove thrust screw anti-rotation pin with a magnet or tweezers. If pin cannot be removed with a magnet or tweezers, proceed with the following procedure:
a. With tool T75P-2588B, force piston approximately one inch from caliper bore.
b. Push piston back into caliper housing with tool, then with tool in position, hold tool shaft in place and rotate handle counter clockwise until thrust screw clears anti-rotation pin. Remove thrust screw and anti-rotation pin.
4. Remove thrust screw by rotating with {1-4} inch Allen wrench.
5. Install tool T75P-2588-A through back of caliper housing and remove piston assembly, Fig. 8. Use care not to damage polished surface in thrust screw bore and do not attempt to remove or press adjuster can, as it is a press fit in piston.
6. Remove and discard piston seal, boot, thrust O-ring seal, end retainer, O-ring and end retainer lip seal.

Fig. 8 Checking Parking Brake Adjuster Operation:

CLEANING & INSPECTION
1. Clean all metal parts with alcohol, then using clean, dry compressed air, blow out and dry all grooves and passages making sure the caliper bore and component parts are free of any foreign material.
2. Inspect caliper bore for damage or excessive wear. The thrust screw must be smooth and free of pits. If piston is pitted, scored or chrome plating is worn, replace piston and adjuster assembly.
3. Adjuster can must be bottomed in piston to be properly seated and provide consistent brake operation. If adjuster can is loose, appears high in piston, is damaged, or if brake adjustment is usually too tight, too loose or not functioning, replace piston/adjuster assembly. Check adjuster operation by assembling thrust screw into piston/adjuster assembly, then pull the two parts apart about {1-4} inch and release them, Fig. 9. When pulling on the two parts, the brass drive ring must remain stationary causing the nut to rotate. When releasing the two parts, the nut must remain stationary and drive ring must rotate. If action does not follow this pattern, replace piston/adjuster assembly.
4. Inspect ball pockets, threads, grooves, bearing surfaces of thrust screw, operating shaft, balls and anti-rotation pin for wear, brinelling or pitting. Replace operating shaft, balls, thrust screw and anti-rotation pin if any of these parts are worn or damaged. A polished appearance on the ball paths is acceptable if there is no sign of wear into the surface.
5. Inspect thrust bearing for corrosion, pitting or wear and replace as necessary.
6. Inspect end plug bearing surface for wear or brinelling and replace as necessary. A polished appearance on bearing surface is acceptable if there is no sign of wear into surface.
7. Inspect operating lever for damage and replace as necessary.

Fig. 9 Filling Piston/Adjuster Assembly:

Fig. 10 Bottoming Piston In Caliper:

ASSEMBLE
1. Coat new caliper piston seal with clean brake fluid and install it in caliper making certain that seal is not twisted and is fully seated in groove.
2. Install new dust boot by seating flange squarely in outer groove of caliper bore, then coat piston/adjuster assembly with clean brake fluid and install it in caliper bore. Spread dust boot over piston as it is installed and seat dust boot in piston groove.
3. Install caliper in vise, Fig. 10, and fill piston/adjuster assembly with clean brake fluid.
4. Coat new thrust screw O-ring with clean brake fluid and install it in thrust screw groove, then install thrust screw into piston adjuster assembly until top surface of thrust screw is flush with bottom of threaded bore, being careful to avoid cutting O-ring seal. Index notches on thrust screw and caliper housing and install anti-rotation pin. The thrust screw and operating shafts are not interchangeable from side to side since the ramp direction in the ball pockets are different. The pocket surfaces of the operating shaft and thrust screws are stamped ``R'' (Right) and ``L'' (Left).
5. Place a ball in each of three pockets of thrust screw and apply a liberal amount of silicone grease M1C-169-A on parking brake components, then install operating shaft on balls.
6. Coat thrust bearing with silicone grease and install it on operating shaft, then install a new lip seal and O-ring on end retainer.
7. Lightly coat O-ring seal and lip seal with silicone grease and install end retainer in caliper. Firmly hold operating shaft against internal mechanism while installing end retainer to prevent mislocation of balls. If lip seal moves out of position, reseat seal. Torque end retainer to 75---95 ft. lbs. Parking brake lever must rotate freely after torquing.
8. Install parking brake lever on keyed spline facing down and rearward. Torque retaining screw to 16---22 ft. lbs.
9. Bottom piston using tool T75P-2588-B, Fig. 11, and install caliper as described previously.