GMC 1976 ZEO 6083 Maintenance Manual page 251

5- 3 2 BRAKES
Figure 42-Positioning Primary Power Piston
16 . Remove the reaction piston and reaction disc
from the center of the secondary power piston by
pushing down on the end of the reaction piston with
a small object, such as a pencil, wooden dowel or
metal rod. (figure 41)
17 . Remove the air valve spring from the end of
the air valve .
18 . Mount Tool J-23101 in a vise with small jaws
Figure 43-Removing Primary Diaphragm
up . Position the primary power piston so that the
two radial slots in the piston fit over the jaws of the
tool . (figure 42)
19 . Fold back primary diaphragm from the sup-
port plate. Grip the edge of the support plate and
rotate in a counterclockwise direction to unlock the
primary support plate from the primary power pis-
ton. (figure 43)
20 . Remove the primary diaphragm from the pri-
mary support plate.
21 . Remove the air filter and push rod limiter
washer from the tubular section of the primary
power piston .
22 . Remove the power head silencer from the
neck of the power piston tube .
23 . Remove the rubber reaction bumper from the
end of the air valve.
24 . Remove the snap ring from the air valve .
(figure 44)
25 . Remove the air valve-push rod assembly from
the tube end of the primary power piston by pulling
on the primary power piston . (figure 45)
26 . Removal of the air valve push rod assembly
will disassemble the floating control valve retainer .
27 . Remove the "O" ring seal from the air valve.
28 . The air valve push rod assembly will be ser-
Figure 44-Removing Snap Ring from Air Valve