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2-32
G R O U P
2-BRAKES
FIG. 31—Valve Operating Rod and Plunger Assembly
14. Remove the O-rings and the
"Block
Vee" type seal from the
valve plunger (Fig. 31).
15. D o not remove the valve op-
erating rod from the control valve
plunger unless the plunger assembly
or the rod is to be replaced. T o re-
move, hold the rod firmly and force
the plunger off the rod, breaking the
plastic
retainer. Remove
all the
broken pieces of the plastic retainer
from the groove in the plunger, i f
the plunger i s to be used again with
a replacement rod.
ASSEMBLY
1. If the valve operating rod was
removed from the plunger, assemble
a new plastic retainer to the end of
the rod (Fig. 26). Insert the rod into
the plunger so that the retainer en-
gages the groove in the plunger.
2. Install the "Block Vee" type
seal and the O-rings on the valve
plunger assembly (Fig. 31).
3. Insert the control valve plung-
er into the control valve hub from
the rear of the hub (Fig. 30).
4. Assemble
the atmospheric
valve, the return spring and the re-
action load ring to the valve plunger
and hub.
5. Push the control valve plunger
assembly
forward and the reaction
load ring backward against the re-
turn spring in order to install the
retainer in the groove of the plunger.
6. Install the O-ring in the groove
at the front side of the diaphragm.
Assemble the valve plunger and hub
assembly to the diaphragm so that
the opening rod and the small-diame-
ter end of the hub enter the front
side of the diaphragm and protrude
from the rear side.
7. Install the "Block Vee" type
seal in the hub rear seal adapter,
with the sealing lip toward the rear.
Slide the seal and adapter assembly
over the rear end of the valve hub
so that the large-diameter side of the
adapter bears against the diaphragm.
8. Install the two plastic plunger
guides in their grooves on the valve
plunger assembly (Fig. 29).
9. Install the rubber reaction ring
in the valve hub so that the ring
locating knob indexes in the notch
in the hub. with the ring tips toward
the front (Fig. 29).
10. Assemble the reaction lever
and ring assembly, then install the
assembly in the valve hub (Fig. 29).
11. Assemble the reaction cone
and cushion ring to the push rod,
and secure to the rod with the re-
tainer (Fig. 26). Install the push rod
assembly to the valve hub so that
the valve plunger indexes in the push
rod (Fig. 29).
12. Assemble the bellows retainer
to the rear fold of the bellows. In-
stall the bellows stay and the two
support rings. The plastic stay i s
located in the center fold of the bel-
lows with a support ring in the fold
at each side of the stay (Fig. 26).
Assemble the bellows protector to
the front fold.
13. Position the bellows assembly
over the push rod against the front
side of the diaphragm. Secure the
bellows to the diaphragm by install-
ing the retainer ring (Fig. 28). M a k e
sure that the retainer ring is fully
seated.
14. Install the O-ring in the groove
at the front side of the end plate.
Assemble the bellows, control valve,
and diaphragm assembly to the end
plate by inserting the valve hub
through the front side of the end
plate with the small diameter side of
the seal adapter protruding from the
rear side of the end plate (Fig. 26).
15. Install the large C-ring to the
rear seal adapter at the rear side of
the end plate.
16. Install the diaphragm return
spring in the booster body, and as-
semble the end plate to the booster
body so that the marks scribed dur-
ing disassembly are in alignment. Be
sure that the lip of the diaphragm is
evenly positioned between the retain-
ing flanges of the booster body and
end plate. Secure the booster body,
diaphragm, and end plate together
with the clamp band, and tighten the
clamp bolt and nut.
17. Pull the front lip of the bel-
lows through the booster body and
position i t around the outer face of
the booster body (Fig. 27)
18. Place the gasket on the end
plate, slide the mounting bracket
over the end plate studs, and install
the retaining nuts (Fig. 26).
19. Slide the rubber boot over the
valve operating rod and engage the
boot with the groove on the mount-
ing bracket.
20. Install the rubber grommet in
the vacuum port in the booster body.
The large diameter side of the grom-
met should be to the outside of the
booster. Force the vacuum manifold
and check valve assembly through
the grommet. D o not push the grom-
met into the vacuum chamber.
21. Install the air filter cover, f i l -
ter, and retainer assembly to the
booster body.
22. Check the booster push rod
adjustment as described
on Page
2-18.
VACUUM BOOSTER FRAME-
M O U N T E D — D I A P H R A G M TYPE
The Midland Hy-Power dia-
phragm type booster used on P-500 -
5000 trucks i s an 81s inch unit
(Fig. 32).
REMOVAL
1. With the engine stopped, de-
press the brake pedal several times to
remove all vacuum from the booster
system.
2. Disconnect the 2 hydraulic lines
and vacuum hose from the booster.
3. O n a frame-mounted booster,
loosen the air breather hose clamp
and disconnect the hose from the
booster, remove the 3 mounting bolts
and
lockwashers and remove the
booster.
O n a frame-mounted booster, do
not remove the breather or the vac-
u u m check valve unless operating
conditions indicate repairs are nec-
essary.
DISASSEMBLY
1. Remove the by-pass tube from
both the control valve body and the
rear body (Fig. 32).
2. Mark both halves of the dia-
phragm body with a scriber. Mark
the flanges of the control valve body
and the slave cylinder body so the
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