GMC 1990 Light Truck Repair Manual page 344

5-8 BRAKES
Primary Piston Assem bly
30.
Snap Ring
31.
Figure 15—Cast Iron Master Cylinder
Components
A stained or discolored cylinder bore with crocus
cloth.
L*
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.
Install or Connect (Figure 19)
• Lubricate all the seals and cylinder bore with clean
brake fluid.
1. Secondary spring (48).
2. Secondary piston assembly (49).
3. Piston return spring (50).
Spring Retainer
26.
27. Primary Seal
28. Secondary Piston
Secondary Seals
29.
Figure 16—Secondary Piston Assembly
Figure 17—Removing Tube Seats
4. Primary piston assembly (51) and snap ring (52).
• The primary piston must be depressed to
install the snap ring.
5. O-ring (55) and springs (47).
6. Valve poppets (46) and compensating valve seals
(45).
F-04397
• Depress and hold the primary piston assembly
with a smooth rounded end tool.
7. Reservoir (44).
NOTICE: See "Notice" on page 5-1 of this
section.
8. Bolts (54).
Tighten
• Bolts to 18 N-m (13 ft. lbs.).
9. Diaphragm (42) into the cover (41).
10. Cover (41).
F-04398
Figure 18—Installing Tube Seats
F-04400