Chevrolet 30 Series 1967 Service Manual page 233

Bail W ire
Reservoir C over
Seal
Body
V a lv e Seat
Inspect primary and secondary cups, valve and valve
seat for damage or swelling. Swelling of rubber
parts is due to the use of improper brake fluid or
washing parts in gasoline or kerosene.
NOTE:
The primary cup has a brass support
ring vulcanized in its base to prevent it from
imbedding in the bleeder holes during braking
action.
Check piston fit in cylinder bore (fig. 29). The
clearance between piston and wall of the cylinder
should be from .001" to .005".
Replace parts as required.
Check clearance between the edge of the primary cup
and the edge of the compensating port. To check this
clearance, proceed as follows:
Fig . 29—Checking M ain C ylin d e r Piston Fit
Fig. 28—Sin g le and C lutch Assist Type C ylin d ers—Exploded V ie w
6. V a lv e Assembly
7. Spring
8. Primary Cup
9. Piston
10. Secondary Cup
.
11
Lock Ring
.
12
Housing
13. Seal
14. Check V a lv e
15. Return Spring
a. Place spring assembly in the housing bore with
the stamped retainer toward the open end of the
bore.
b. Place primary cup over the spring, with the flat
side outward.
c. Using the piston push the cup inward sufficiently
to allow assembly of the piston stop snap ring,
then release piston against snap ring.
d. Insert a straight wire (tag wire, or any wire of
approx. dia.) through the small compensating
. 0 2 0
port into the housing bore (fig. 30).
e. While moving the wire back and forth in the com­
pensating port, push the piston inward very gently
until a slight drag on the wire is felt.
f. Check clearance between the end of the piston and
the snap ring. This clearance should be .035
Fig . 30—M ain C y lin d e r—Cross Section
BRAKES 5-17
16. Retainer
17. Primary Cup
18. Piston
19. Piston Seal
20. Snap Ring
CHEVROLET TRUCK SERVICE M ANUAL