Tandem Diaphragm Vacuum Booster - Chevrolet 1988 Light Duty Truck Repair Manual

Lubricate the inside and outside diameters of
the grom met and front housing seal with a thin
layer of silicone.

TANDEM DIAPHRAGM VACUUM BOOSTER

R em ove or D is c o n n e c t (F ig u re 25)
Tool Required:
J 23456 Power Brake Booster Disassembly
and Reassembly Fixture
1
Boot ( ) and silencer (2).
Vacuum check valve (3) and grom m et (4).
Front housing seal (7).
Scribe a mark on the front and rear housings to aid
in assembly.
Unlock the front and rear housings using J 23456
2 1
(figure ).
Return spring (11) and power piston group (38) (fig­
ure 26).
8
Prim ary piston bearing (
Piston rod (12), reaction retainer (13) and power
head silencer (14).
Power piston assembly (41) along with the pushrod
(32) (figure 27).
• Grasp the assembly at the outside edge of the
housing divider (19) and diaphragm s (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).
Primary diaphragm (16) and prim ary support plate
(17) from the housing divider (19).
Primary diaphragm (16) from the prim ary support
plate (17).
10 Secondary diaphragm (20) and secondary support
.
plate (21) from the housing divider (19).
11.
Secondary piston bearing (18) from the housing d i­
vider (19).
) from the rear housing (9).
Figure 24 — Gaging the Piston Rod
11. Front housing seal (5).
12. Silencer (2) and boot (1).
• Gage the piston rod using J 22647 (figure 24). If not
within limits, obtain a service adjustable piston rod.
12 Secondary diaphragm (20) from the secondary sup­
2 1
port plate ( ).
Reaction body retainer (24).
13.
14.
Reaction body (25).
15. Reaction disc (22) and reaction piston (23) from the
reaction body (25).
16. Air valve spring (26) and reaction bum per (27) from
the end of the air valve pushrod (32).
17.
Retaining ring (28) from the air valve pushrod as­
sembly (32).
18. A ir valve pushrod assem bly (32) by inserting a
screwdriver through the pushrod eyelet and pulling
it straight out.
• Considerable force will be required.
Filter (29), retainer (30) and O-ring (31) from the air
19
valve pushrod assembly (32).
1 3
Inspect
All parts for corrosion, nicks, cracks, cuts, scoring,
distortion or excessive wear. Replace parts as nec­
essary.
Use crocus cloth to polish away minor corrosion of
the housings or diaphragm support.
Clean
All parts in clean denatured alcohol.
— Do not immerse the power piston and pushrod
assembly in alcohol.
Dry with unlubricated compressed air.
Install or C on n ect (F ig u re 25)
Tools Required:
J 23456 Power Brake Booster Disassembly
and Reassembly Fixture
BRAKES 5-11
F-05891