GMC 1990 Light Truck Repair Manual page 345

Delco-Moraine Vacuum Boosters have a build date on a
small paper label glued onto the front housing. The first
digit indicates the year it was built (a 5 means 1985 or a 6
SINGLE DIAPHRAGM VACUUM BOOSTER
♦ + Remove or Disconnect (Figure 20)
Tool Required:
J 23456 Power Brake Booster Disassembly
and Reassembly Fixture
1. Boot (1) and silencer (2).
2. Vacuum check valve (3) and grommet (4).
3. Front housing seal (5).
• Scribe a mark across the front and rear housings to
aid in assembly.
• Use J 23456 to apply force in a counter clockwise
direction to unlock the housings (figure 21).
4. Return spring (9) and power piston group.
5. Power piston bearing (6) from the rear housing (7).
6. Reaction body retainer (25).
7. Piston rod (10) and reaction retainer (11).
8. Filter (12) using an awl or similar tool.
9. Power piston and pushrod assembly (16).
Figure 19—Bendix Master Cylinder Components
VACUUM BOOSTERS
Cover
Diaphragm
Filter
Reservoir
Com pensating Valve Seal
Valve Poppet
Spring
Secondary Spring
Secondary Piston
Piston Return Spring
Primary Piston
Snap Ring
Body
Bolts
O-Ring
means 1986). The last digits indicate the day it was built
(271 means the 271st day of production year).
• Grasp the outside edge of the diaphragm sup­
port (15) and diaphragm (14). Hold the
pushrod (19) down against a hard surface.
• Use a slight force or impact to dislodge the
diaphragm retainer (13).
10
Diaphragm (14) from the diaphragm support (15).
.
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.
a y
Clean
All parts in clean denatured alcohol.
— Do not immerse the power piston and pushrod
assembly in alcohol.
Dry with unlubricated compressed air.
BRAKES 5-9
F-00775