Repair Procedure

This repair involves replacement of the actuator piston assemblies with revised pistons.

WARNING:
FAILURE TO DE-PRESSURIZE THE HYDRAULIC ACCUMULATOR, BEFORE DOING THIS REPAIR, MAY RESULT IN PERSONAL INJURY AND/OR DAMAGE TO PAINTED SURFACES. WEAR SAFETY GOGGLES WHEN DISCONNECTING FLUID LINES. KEEP WORK AREA CLEAN. AVOID CONTAMINATION OF SYSTEM COMPONENTS WITH DIRT OR FOREIGN MATERIAL. USE CLEAN BRAKE FLUID SUCH AS MOPAR OR EQUIVALENT, CONFORMING TO DOT 3 REQUIREMENTS.



1. With the ignition key in the OFF position, discharge the ABS accumulator by pumping the brake pedal 40 times.

2. Remove the hydraulic unit from the vehicle as outlined in the appropriate service manual, and place on a clean, dry work bench.





3. Secure the hydraulic unit in a vise, see Figure 1. Do not over tighten.



4. Remove the flange gasket from the hydraulic assembly mounting bracket/dash board.

5. Loosen the dash mounting bracket from the hydraulic actuator assembly enough to separate the black dust boot from the actuator housing, retighten bracket.





6. Place a 1/2" box end wrench over the lower mounting stud of the hydraulic unit, see Figure 2. Place a nut onto the stud and turn it enough to engage the threads 100%. Make sure that the wrench is aligned, as illustrated in Figure 2, on the input rod bearing.



7. Push in on the wrench against the bearing, moving the bearing inward approximately 1/4", to relieve the bearing load from the snap ring.





8. Rotate the open end of the snap ring near the 12 o'clock position. Place a small screwdriver in the 12 o'clock keyway on the actuator, Figure 3. Pry the snap ring down and out of the groove with the screwdriver and pull the snap ring out of end of the actuator. Discard the snap ring.



9. Slowly release the wrench from the bearing, allowing the primary piston assembly to pop out. Catch any fluid from the actuator bore in a suitable container as the primary piston is removed.

10. Slowly pull the piston out of the actuator bore, keep the assembly as straight as possible. Do not pull forcefully, (if piston catches in the bore, push the piston back into the bore a short distance to align, and try again to remove the piston).


NOTE:
IF THE PISTON STILL WILL NOT COME OUT OF THE ACTUATOR BORE THEN THE ACTUATOR HOUSING MUST BE REPLACED.





11. Remove the hydraulic assembly from the vise and place, stud side down, on a bench on a lint free cloth, see Figure 4.






12. Place a cloth over the outlet ports of the unit. While holding the cloth in place, apply pressure from a regulated air nozzle to the front of the actuator, to expel the secondary piston assembly from the bore onto the cloth on the bench, see Figure 5.



13. Place the hydraulic unit back into the vise and clamp securely.

14. Using the swab provided, apply clean brake fluid and thoroughly clean the bore of the hydraulic unit. Wipe the entire circumference of the bore and work any particles toward the open end of the bore. Flush the bore, after swabbing, with clean brake fluid.

15. Using clean brake fluid, lubricate the new pistons. Wet the cup seals, white ring seals and the o-rings.








16. Install the secondary piston, spring end first, into the actuator bore, see Figure 6. Ensure the seal cup is not folded back or twisted. Push the secondary piston in until the rear end of the piston is flush with the actuator bore opening, see Figure 7.



17. Position the caged spring at the end of the primary piston assembly over the pin on the rear of the secondary piston, see Figure 6. The caged spring must remain over this pin, throughout the installation procedure.

18. Slowly, push both piston assemblies into the actuator bore. Do not cut, nick or twist any of the seals, or the unit will not function properly.

19. Place the new snap ring over the master cylinder push rod and bearing.

20. Push the piston assemblies all the way into the bore, compressing the springs. The shoulder of the bearing should be in past the snap ring groove.

21. Secure the piston in the bore with a nut and wrench, in the same manner as used during removal of the snap ring.





22. With the keyway at the top of the bore, in the 12 o'clock position, position the snap ring so that one end is in 10 o'clock position and the other end is in the 8 o'clock position, see Figure 8. The snap ring should cover the keyway at the 12 o'clock position.

23. Place the 10 o'clock end of the snap ring into the snap ring groove. Use a flat blade screwdriver, push the snap ring into the groove, working in a clockwise direction. Ensure the snap ring and both ends are seated completely into the groove.

24. Slowly release the wrench, then remove the nut and wrench from the stud.



25. Loosen the dash mounting bracket from the hydraulic unit. Install the rubber dust boot over the actuator bore flange and seat the retaining ring into the groove and retighten bracket.



26. Install the hydraulic unit, with new mounting gasket, as outlined in the appropriate service manual.

27. Ensure the brake system is functioning as designed.