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BRAKES
5-45
Fig. 5-72 Positioning Housing Divider Over Secondary
Bearing Protector Tool J 23 188
on the diaphragm is seated evenly around the complete
circumference.
40.
Wipe a thin film of silicone lubricant on the O.D.
of the piston rod retainer. Insert the master cylinder piston
rod retainer into the cavity in the secondary power piston so
that the flat end bottoms against the rubber reaction disc in
the bottom of the cavity.
Reassembly of Rear Housing Group
1. Place the primary power piston bearing in rear
housing center hole so that the formed flange of the housing
center hole fits into the groove of the primary power piston
bearing. The thin lip of the bearing will protrude to the
outside of the housing.
2. Coat the I.D. of the primary power piston bearing
with silicone lubricant.
Final Assembly
1. Mount the front housing assembly in a vise.
2.
Position the power piston return spring over the inset
in the front housing.
3.
Assemble the power piston group to the rear housing
by pressing the tube of the primary piston through the rear
housing bearing. Press down until the housing divider seats
in the rear housing and the primary power piston bottoms
against the housing.
4.
Place the piston rod retainer plate on the end of the
power piston return spring in the front housing.
5.
Hold the rear housing assembly (with mounting studs
up) over the front housing. (Make sure that the piston rod
retainer does not dislodge from the secondary power piston
during this operation.) Position the rear housing so that when
the tangs on the edge of the front housing are locked in the
slots on the edge of the front housing, the scribe marks on
the top of the housings will be in line.
6.
Lower the rear housing assembly onto the front
housing. The power piston spring must seat in the depression
in the face of the secondary power piston. Check that the bead
on the O.D. of the secondary diaphragm is positioned
between the edges of the housing.
7.
Continue to press down on the rear housing and fit
the slots in the appropriate tangs on the front housing.
8. To facilitate locking, position front housing seal in the
depression in the front housing and apply a vacuum source
to the vacuum check valve in the front housing. Using Tool
J
23456,
press down and rotate the rear housing clockwise
into the locked position. Remove Tool J 23456; remove the
vacuum source. See Fig. 5-60.
9. Place the silencer in the closed end of the power head
boot. Push the boot retainer over the boot. Stretch the boot
over the push rod and over the flange in the center of the rear
housing.
GAGING DELCO MORAINE TANDEM
POWER BRAKE UNIT
1. Place the power head assembly in a padded vise (front
housing up). Do not clamp tight.
2.
Insert the master cylinder piston rod, flat end first,
into the piston rod retainer.
3.
Press down on the master cylinder piston rod (with
approximately a 40-50 pound load) to be sure it is properly
seated.
4.
Remove the front housing seal to assure that no
vacuum is in the power head will gaging.
5.
Place Gage J 22647 over the piston rod in a position
which will allow the gage to be slipped to the left or right
without contacting the studs. See Fig. 5-73.
Fig. 5-73 Gaging Piston Rod
6.
The center section of the gage has two levels. The
piston rod should always contact the longer section (lower
level) of the gage. The piston rod should never contact the
shorter section (higher level) of the gage. Move gage from side
to side to check piston rod height.
7.
Any variation beyond these two limits must be
compensated for by obtaining the service adjustable piston
rod and adjusting the self-locking screw to meet the gaging
specifications.
8. Wipe a thin film of silicone lubricant on the I.D. of
the front housing seal and position seal in the depression in
the housing.
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