Chevrolet 1991 Light Duty Truck Repair Manual page 332

5-12 BRAKES
• Scribe a mark on the front and rear housings to
aid in reassembly.
• Unlock the front and rear housings using J 23456
(figure 21).
4. Return spring (11) and power piston group (38)
(figure 26).
5. Primary piston bearing (8) from the rear housing
(9).
6. Piston rod (12), reaction retainer (13) and power
head silencer (14).
7. Power piston assembly (41) along with the pushrod
(32) (figures 25 and 27).
• Grasp the assembly at the outside edge of the
housing divider (19) and the diaphragms (16
and 20).
• Hold with the pushrod (32) down against a hard
surface.
• Use a slight force or impact to dislodge the
diaphragm retainer (15).
8. Primary diaphragm (16) and primary support plate
(17) from the housing divider (19).
9. Primary diaphragm (16) from the primary support
plate (17).
1. Boot
2. Silencer
3. Vacuum Check Valve
4. Grommet
7. Front Housing Seal
8. Primary Piston Bearing
9. Rear Housing
10. Front Housing
11. Return Spring
12. Piston Rod (Gaged)
13. Reaction Retainer
14. Power Head Silencer
15. Diaphragm Retainer
16. Primary Diaphragm
17. Primary Support Plate
18. Secondary Piston Bearing
19. Housing Divider
20. Secondary Diaphragm
21. Secondary Support Plate
22. Reaction Disc
23. Reaction Piston
24. Reaction Body Retainer
25. Reaction Body
26. Air Valve Spring
27. Reaction Bumper
28. Retaining Ring
29. Filter
30. Retainer
31. O-Ring
32. Air Valve Push Rod Assembly
33. Power Piston
41. Power Piston Assembly
Figure 25—' T andem Diaphragm Vacuum Booster Components
10. Secondary diaphragm (20) and secondary support
plate (21) from the housing divider (19).
11. Secondary piston bearing (18) from the housing
divider (19).
12. Secondary diaphragm (20) from the secondary
support plate (21).
13. Reaction body retainer (24).
14. Reaction body (25).
15. Reaction disc (22) and reaction piston (23) from
the reaction body (25).
16. Air valve spring (26) and reaction bumper (27)
from the end of the air valve pushrod (32).
17. Retaining ring (28) from the air valve pushrod
assembly (32).
18. Air valve pushrod assembly (32) by inserting a
screwdriver through the pushrod eyelet and pull
the assembly straight out.
• Considerable force will be required.
19. Filter (29), retainer (30) and O-ring (31) from the air
valve pushrod assembly (32).
F9157