Chevrolet 1977 10 Series, Repair Manual, Page: 188 / 468

5-22 OVERHAUL MANUAL
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, R E PL A C E them.
Inspecting Metal Parts
BADLY D A M A G E D ITEM S, O R TH O SE W H IC H
W O U LD T A K E EX TEN SIV E W O R K O R T IM E TO
R E PA IR , SH O U LD BE R E PL A C E D . 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.
Assembly (Figs. 5-1D and 5-2D)
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
silicone lubricant provided in the service repair kit.
Front Housing Group
1. Install new check valve grommet in front housing with
beveled edge of grommet inside of housing. Dip new check
valve in clean denatured alcohol and install in grommet--
check valve stem is to be outside of housing.
2. Position and secure Holding Fixture J-22805 to
mounting studs, and place tool and front housing in a vise.
Be sure to align tool so that check valve is not damaged.
NOTE:
If either or both of the housings are replaced,
make sure alignment marks are transferred to the new
housing.
Rear Housing Group
1. Place rear housing on a block of wood, stud side down,
and position housing seal in center hole. Use Tool J-22677
(fig. 5-4D) to seat seal in recess of rear housing. Tool bottom s
against housing when seal is in place.
2. Assemble diaphragm plate assembly (see fig. 5-2D).
a. Apply silicone lubricant to outside diam eter of
diaphragm plate and extension, to bearing surfaces of air
valve and to outer edge of valve poppet. Insert air valve and
push rod assembly in extension of diaphragm plate.
NOTE:
The air valve, poppet valve and push rod are
serviced as an assembly; a complete unit must be
installed if there is damage to any of the component
parts.
b. Depress the push rod slightly and install the air valve
lock. Make sure the lock indexes and retains the air valve.
c. Install the rolling diaphragm in the groove of
diaphragm plate.
d. Apply silicone lubricant to surface of reaction disc and
position disc in center bore of diaphragm plate. Use piston
rod to seat disc in bore. Make sure disc is fully seated before
removing piston rod.
NOTE:
If reaction disc is not fully seated, it will result
in an erroneous push rod height adjustment.
3. Apply silicone lubricant to I.D . of rear housing seal
and diaphragm bead contact surface of rear housing. Install
diaphragm plate assembly in rear housing.
4. Place air filter element over push rod and into
diaphragm plate extension. Install filter retainer.
Fig. 5 -4 D —In s ta llin g Rear H o u sin g Seal
Final Assembly
1. A ttach base of Holding Fixture J-22805 to front
housing with nuts and washers and draw down tight to
eliminate bending or damage to studs. Clamp base in bench
vise with power section up (fig. 5-2A).
CAUTION:
Be sure to align tool so that the check
valve in the front housing is not damaged.
2. Place Spanner W rench J-9504 over studs on rear
housing and attach with nuts and washers. Draw nuts down
tight to eliminate bending or damaging of studs.
3. Place diaphragm plate return spring in front housing
and position rear housing assembly on front housing (small
end of spring downward). Position rear housing so that when
housings are locked, scribe m arks on front and rear housings
will be in alignment.
4. Press down on Spanner W rench J-9504 and rotate the
rear housing counterclockwise to assemble the two housings.
CAUTION:
Bend lances in on the rear housing. I f
the tangs crack or break during this operation it will
be necessary to replace that h a lf o f the housing.
5. Remove Tool J-9504 from the rear shell.
6. Install air silencers over push rod end and then install
push rod boot. Install boot retainer.
7.
Clevis Type Push Rod
- Install locknut and push
rod clevis.
8. Install m ounting bracket to the rear shell, if so
equipped.
CAUTION:
See "Caution " on Page 1 o f this section.
9. Remove power cylinder from vise and remove
Holding Fixture J-22805.
10. Apply silicone lubricant sparingly to the piston rod,
keeping lubricant away from rounded end of rod. Guide
piston rod into center bore of the diaphragm plate until it is
fully seated against reaction disc.
11. Install front housing seal. Press seal into front
housing until seal is bottom ed in recess of housing.