Vacuum Brake Booster: Service and Repair

Fig. 10 Brake Booster Removal:

Fig. 3 Exploded View Of AC-Delco Single Diaphragm Booster:

Fig. 11 AC-Delco Brake Booster Holding Tools:

DISASSEMBLE
1. Remove booster pushrod clevis and adjustment nut from air valve assembly, Fig. 10 .
2. Using pliers, flatten two index tabs which fall between the two raised points on opposite sides of perimeter of both booster halves, Fig. 3 .
3. Mount booster in a vise with holding tool No. J-23456 and J-23456-51A, or equivalents, Fig. 11 . Tighten fixture enough to secure booster and allowing rotation of booster front half.
4. Scribe a mark across both booster halves to facilitate final assembling.
5. Using turning tool No. J-23456, or equivalent, rotate front half of booster until all indexing tabs are aligned with indention on rear half of booster.
6. Slowly loosen the tool center screw and separate booster halves.
7. Remove both booster halves, booster piston return spring and piston rod, and retainer from holding fixture.
8. Remove body boot, two air cleaner elements and booster piston from piston groove.
9. Remove valve stopper key from booster piston while working air valve in and in-and-out motion.
10. Using seal tools No. J-34874, J-7079-2 and J-35379 or equivalents, drive rear booster half seal out with a hammer.
11. Replace any parts that are corroded, nicked, scored, distorted or excessively worn.

ASSEMBLE
1. Before installation, apply a liberal coat of silicone grease to the following:
a. Inside of rear booster half oil seal.
b. Entire surface of reaction disc.
c. Outside of air valve assembly seal.
d. Entire surface of diaphragm.
e. Sliding surface of air valve
2. Using seal tools No. J-34874, J-7079-2 and J-35379 or equivalents, drive new rear booster half seal in with a hammer.
3. Install reaction disc to piston rod, then air valve assembly to booster piston, diaphragm booster piston by hand.
4. Install valve stopper key to booster piston while compressing air valve assembly.
5. Install booster rear half, then both air cleaner elements to air valve assembly.
6. Secure body boot on rear booster body and air valve assembly, then rear booster half to holding tool No. J-23456 and J-23456-51A, or equivalents.
7. Assemble piston rod, piston rod retainer and piston return spring to rear booster, then front booster to rear half aligning piston return spring.
8. Tighten center screw of tool No. J-23456, or equivalent, bringing both booster halves together. Ensure both halves mate squarely and align with indexing tabs in rear halve indentation.
9. Rotate front half of booster using the tool until the twelve indexing tabs catch under lip of rear half of booster.
10. Align scribe mark made prior to disassembling, then remove booster assembly from tools.
11. Using pliers, reposition any flattened indexing tabs to secure assembly.