GMC S Series 1994, Repair Manual

Page: 290 / 919

8. P rim a ry P is t o n B e a rin g
F5823
Figure 6— Booster Inner Components
2. Vacuum check valve (3) and grommet (4).
3. Front housing seal (7).
4. Scribe a mark on front and rear housings to aid in
assembly.
5. Unlock front and rear housings (figure 1).
A. Set booster in disassembly tool J 23456.
B. Tighten fixture hand screw just enough to allow
housing to rotate.
C. Apply force in a counterclockwise direction to
unlock housings.
D. Back off fixture hand screw and housings will
separate.
6. Return spring (11) and power piston group (38)
(figure 6).
7. Primary piston bearing (8) from rear housing (9).
8. Piston rod (12), reaction body retainer (24), and
reaction retainer (13).
9. Power head silencer (14).
10. Power piston assembly (41) along with the pushrod
(32).
A. Grasp assembly at outside edge of housing
divider (19) and diaphragms (16 and 20).
B. Hold assembly with pushrod (32) down against
a hard surface.
C. Use a slight force or impact to dislodge dia­
phragm retainer (15).
11. Primary diaphragm (16) and primary support plate
(17) from housing divider (19).
12. Primary diaphragm (16) from the primary support
plate (17).
13. Secondary diaphragm (20) and secondary support
plate (21) from housing divider (19).
12. Piston Rod
(Gaged)
13. Reaction
Retainer
14. Power Head
S ilencer
15. Diaphragm
Retainer
16. Primary Diaphragm
17. Primary Support Plate
18. Secondary Piston Bearing
19. Housing Divider
20. Secondary Diaphragm
21. Secondary Support Plate
41. Power Piston Assem bly
F5893
Figure 7— Power Piston Group
14. Secondary piston bearing (18) from housing divider
(19).
15. Secondary diaphragm (20) from secondary support
plate (21).
16. Reaction body (25) from power piston (33).
17. Reaction disc (22) and reaction piston (23) from
reaction body (25).
18. Air valve spring (26) and reaction bumper (27) from
end of air valve pushrod (32).
19. Retaining ring (28) from air valve pushrod assem­
bly (32).
20. Air valve pushrod assembly (32) by inserting a
screwdriver through pushrod eyelet and pulling
straight out.
• Considerable force is required.
21. Filter (29), retainer (30), and O-ring (31) from air
valve pushrod assembly (32).
1?
Inspect
• All parts for corrosion, nicks, cracks, cuts, scoring,
distortion, or excessive wear. Replace as needed.