B. Replace Master Cylinder Primary Piston

1. Clean master cylinder and attaching area of power brake booster with Mopar Glass Cleaner PN 4318014.

2. 2.4L engine equipped vehicles: Remove the air cleaner resonator/housing for greater access to master cylinder.

3. Speed control equipped vehicles: Remove mounting nuts and set speed control servo aside for greater access to master cylinder.

4. Disconnect wiring to master cylinder reservoir brake fluid level sensor.

5. Disconnect the primary and secondary brake tubes from master cylinder. Install provided plugs into master cylinder outlet ports and cap the brake tubes.

Note:
DO NOT drip brake fluid on painted surfaces as this may damage paint.

6. Remove the two nuts attaching the master cylinder to the brake booster. Slide the brake tube mounting bracket from the inboard master cylinder mounting stud and slide master cylinder off the brake booster mounting studs.

7. Drain brake fluid from the master cylinder reservoir.

8. Clamp master cylinder in a vice at the mounting flange area. Thoroughly clean master cylinder and reservoir with Mopar Glass Cleaner PN 4318014 and wipe with a clean cloth.

Caution:
DO NOT use this cleaner on any internal master cylinder components or on the master cylinder piston bore.





9. ABS equipped vehicles only: Using a screw driver, pry away from the fluid level sensor and remove reservoir from master cylinder as shown in Figure 2. Be careful not to damage the fluid level switch and KEEP MASTER CYLINDER CLEAN AT ALL TIMES.

10. ABS equipped vehicles only:





a. Remove and discard only the rear reservoir grommet and note which hole the primary piston retaining pin is in (Figure 3).





b. Remove the master cylinder from the vice and turn the master cylinder upside down. Using the provided dowel rod, stroke the piston to allow the retaining pin to fall out, then remove the primary piston (Figure 4). Discard the old pin and piston.

Note:
If necessary, use a magnet while stroking the piston to remove the pin. Piston removal may require air pressure. Apply compressed air (regulated to about 20 psi) to the primary outlet, while blocking the rear reservoir opening. Be sure to wear safety goggles.





11. NON-ABS equipped vehicles only: Using the supplied dowel rod1 stroke and hold the primary piston and remove the snap ring from the rear of the master cylinder, then remove the primary piston (Figure 5). Discard the old piston and snap ring.

Caution:
Be careful not to damage cylinder bore when using snap ring pliers.

Note:
Piston removal may require air pressure. Install the reservoir cap and apply compressed air (regulated to about 20 psi) to one primary outlet, while blocking the other primary outlet. Be sure to wear safety goggles.

12. With CLEAN HANDS, rinse the inside of the master cylinder and lubricate both of the seals on the new primary piston assembly with clean brake fluid conforming to DOT 3 specifications. Insert the new piston assembly spring end first.

Note:
ABS pistons must be installed with the piston slot in a vertical position to allow for piston pin installation (Figure 4).

13. ABS equipped vehicles only:





a. Using supplied dowel rod, stroke and hold the primary piston approximately 3/4 inch. Insert new retaining pin into the same hole in master cylinder body that the original retaining pin was in (Figure 3). When inserted properly, the end of pin should be almost flush with master cylinder surface (Figure 6).

b. Remove front reservoir grommet from the master cylinder body and discard. Verify that both primary and secondary piston pins are seated (end of pins are almost flush with surface as shown in figure 6). Lubricate two provided reservoir grommets with clean brake fluid and install grommets into the master cylinder body.

c. Install reservoir onto master cylinder body using a rocking motion (fluid level sensor must be on outboard side when installed in vehicle). There must be no reservoir-to-grommet gaps, or grommet-to-master cylinder body gaps. If gaps exist, the piston pins may not be fully inserted (Figure 6).

Caution:
Make sure piston pins are inserted properly and that the grommets do not contact the ends of either pin. Failure to insert pins will cause brake drag.

14. NON-ABS equipped vehicles only: Using the supplied dowel rod, stroke and hold the primary piston assembly beyond the snap ring groove in the master cylinder body and install provided snap ring (Figure 5).

Caution:
Make sure snap ring is fully seated in groove. Be careful not to damage cylinder bore when using snap ring pliers.





15. Attach Miller Special Tool # 6802 bleed tubes to primary and secondary outlets and position tubes so the outlets will be submerged in brake fluid when reservoir is filled. Fill master cylinder reservoir with clean brake fluid conforming to DOT 3 specifications. Bench bleed master cylinder by using the provided dowel rod. Slowly depress pistons with dowel rod1 then allow pistons to return to the fully released position. Repeat this step several times after no air bubbles are expelled from the bleed tubes. This will insure all air is bled from the master cylinder (Figure 7).

Note:
DO NOT install the master cylinder without following the above bench bleeding procedure. When this procedure is followed, it is not necessary to bleed the entire vehicle brake system.

16. Remove the bleed tubes from the master cylinder outlet ports. Verify that brake fluid drips from both the primary and secondary outlet ports. Plug outlet ports with the supplied plugs, top off reservoir with brake fluid and install reservoir cap.

Note:
If brake fluid does not drip from the primary and/or secondary outlet ports, the master cylinder must be disassembled and the appropriate compensation port cleaned. On ABS master cylinders, no fluid dripping from an outlet port may also be caused by a missing/damaged piston pin or damaged piston center valve.

17. Install master cylinder assembly onto power brake booster studs. Align brake booster push rod with hole in master cylinder primary piston, then seat master cylinder against booster. Slide brake tube support bracket onto inboard mounting stud. Torque two attaching nuts to 250 in-lbs (28 N.m).

18. Remove master cylinder and brake tube plugs and attach brake tubes to master cylinder. Torque tube nuts to 145 in-lbs. (17 N.m).

19. Attach wiring connector to reservoir brake fluid level sensor.





20. Verify proper brake warning lamp operation by removing the reservoir cap and using the provided dowel rod (make sure rod is clean) to push the float to the bottom of its travel (Figure 8). With the key in the ON position and the float at the bottom of its travel the warning light should be illuminated. Reinstall reservoir cap.

21. With engine off, pump brake pedal about 3-4 times until all vacuum in power brake booster is depleted. Apply light brake pedal pressure and hold for a minimum of 30 seconds. The brake pedal should remain firm. Apply heavy brake pedal pressure and hold for a minimum of 30 seconds. Again, the brake pedal should remain firm. If the brake pedal drops or is not firm during either of these tests, the master cylinder may either have a damaged piston assembly or it was not properly bled and must be repaired accordingly.


22. Speed control equipped vehicles: Install speed control servo and tighten nuts securely.


23. 2.4L engine equipped vehicles: Install air cleaner resonator/housing.


24. Verify that no brake fluid leaks exists and road test vehicle to assure proper brake operation.