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BRAKES
5-43
Fig. 5-69 Removing Retaining Ring From Air Valve
kerosene, anti-fieeze, alcohol or any other cleaner,
with even a trace ofmineral oil, will damage rubber
parts.
Inspecting Rubber Parts
Wipe fluid from the rubber parts and carefully inspect
each rubber part for cuts, nicks, or other damage. These parts
are the key to the control of fluid or air flow, if the unit is
in for overhaul, or if there is any question as to the
serviceability of rubber parts, REPLACE them.
Inspection Metal Parts
BADLY DAMAGED ITEMS, OR THOSE WHICH
WOULD TAKE EXTENSIVE WORK OR TIME TO
REPAIR, SHOULD BE REPLACED. In case of doubt,
install new parts. Do not rely on the brake unit being
overhauled at an early or proper interval. New parts will
provide more satisfactory service, even if the brake unit is
allowed to go beyond the desired overhaul period.
REASSEMBLY OF DELCO MORAINE
TANDEM POWER BRAKE UNIT
General
1. Be careful during the rebuild procedure that no grease
or mineral oil comes in contact with the rubber parts of the
power brake unit.
2. Lubricate power head parts, as outlined below, with
power brake silicone lubricant. This lubricant is provided in
the service repair kit.
Reassembly of Front Housing Group
1. If the grommet was removed for replacement, insert
the new grommet in the front housing.
2. Press the vacuum check valve through the grommet.
Reassembly of Power Piston Group
1. Lubricate the I.D. and O.D. of the " 0 " ring seal with
silicone lubricant and dace on the air valve.
2. Wipe a thin film of silicone lubricant on the large and
small O.D. of the floating control valve.
3. If the floating control valve needs replacement, it will
be necessary to replace the complete air valve push rod
assembly, since the floating control valve is a component part
of this assembly and cannot be disassembled from the push
rod.
:ig. 5-70 Installing Floating Control Valve Retainer With
Installer
J
2 3 1 7 5
4. Place the air valve end of the air valve vush rod
assembly into the tube of the primary power piston. Manually
press the air valve push rod assembly so that the floating
control valve bottoms on the tube section of the primary
power piston. Installer tool J 23 175 can be used to manually
press the floating control valve to its seat.
5. Place the I.D. of the floating control valve retainer on
the O.D. of floating control valve retainer installer J 23175.
See Fig. 5-70. Place over the push rod so that the closed side
of the retainer seats on the floating control valve. With
Installer J 23 175, manually press the retainer and floating
control valve assembly to seat in the primary power piston
tube. See Fig. 5-71.
6. After the floating control valve is seated, place the
push rod limiter washer over the push rod and position on
the floating control valve.
7. The filter element can now be streached over the push
rod eye and pressed into the primary power piston tube.
8. Using Truarc No. 2 plier (J 4880), place the retaining
ring into the groove in the air valve. See Fig. 5-69.
9. Position the rubber reaction bumper on the end of the
air valve.
10. Tolerances of those component parts a f f d i n g output
of the tandem power brake are very critical. Always use the
factory gauged power piston kit, containing both the primary
and secondary power pistons with factory gauged reaction
piston, when replacement of any of these parts is required.
12. After determination of the correct reaction piston,
apply a light film of silicone lubricant to the O.D. of the
rubber reaction disc.
13. Place the rubber reaction disc in the large cavity of
the secondary power piston and push the disc down to seat
on the reaction piston.
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