GMC T Series 1994 Repair Manual page 283

Figure 2— Composite Master Cylinder Components
CAUTION: If air pressure is used to remove
the secondary piston, place the open end of
the cylinder bore approxim ately 25 mm (1
inch) from a padded workbench or other sur­
face to catch the piston when it comes out of
the bore. Apply low air pressure very careful­
ly to ease the piston out of the bore. Never
point the open end of the bore at anyone
when applying air pressure. The piston may
come out of the bore with considerable force
and cause personal injury.
7. Secondary piston (9).
• With the rear port plugged, apply a small
amount of air pressure to the front port.
8. Seals (8 and 10).
9. Spring retainer (7) and spring (6).
X jjJ I
Clean
All metal parts in denatured alcohol.
All rubber parts in clean brake fluid.
Stained or discolored cylinder bore with crocus
cloth.
1. Cover
2. Diaphragm
3. Reservoir
4. Grommet
5. Quick Take-Up
Valve
6. Spring
7. Spring Retainer
8. Primary Seal
9. Secondary Piston
10. Secondary Seal
11. Snap Ring
12. Primary Piston
Assem bly
Body
F0770
Figure 3— Removing the Reservoir
Inspect
Diaphragm for cuts, cracks, or a swollen condition.
Cylinder bore for scoring or corrosion.
— If corrosion is present, replace the cylinder.
— Do not attempt to hone the bore.
Reservoir for cracks.
Install or Connect (Figures 1, 2, 4, and 5)
Lubricate the grommets, seals, and cylinder bore
with clean brake fluid.
1. Spring (6) and spring retainer (7).
2. Seals (8 and 10) on the secondary piston (9).
3. Secondary piston (9).
4. Primary piston assembly (12).