Chevrolet Chevelle 1977 Repair Manual page 189

Fig. 5 -5D --G auging P iston Rod
Gaging
1. Place the power head assembly in a padded vise (front
Do not clamp tight!
housing up).
BENDIX HYDRAULIC BRAKE BOOSTER (HYDRO-BOOST)
The Bendix Hydraulic Brake Booster utilizes the
hydraulic pressure supplied by the power steering pum p to
provide power assist for brake applications (fig. 5-IE). The
dual master cylinder is mounted to the output push rod end
of the booster.
The procedures below include removal of the m ounting
bracket even though it is not necessary to remove the bracket
for overhaul of the internal assembly.
Disassembly (Fig. 5*2E)
1. Secure the booster in a vise (bracket end up) and use
a ham m er and chisel to cut the bracket nut that secures the
PRESSURE PORT
RETURN PORT
ACCUMULATOR
OUTPUT PUSH ROD
BOOSTER POWER SECTION
Fig. 5-1E--Bendix Hydro-Boost Brake Booster
BRAKES
UNIT REPAIR
PEDAL ROD
MOUNTING BRACKET
2. Remove the front housing seal to assure that no
vacuum is in the power head while gaging.
3. Insert the master cylinder piston rod, flat end first,
into the piston rod retainer.
4. Press down on the master cylinder piston rod (with
approximately a 40-50 pound load) to be sure it is properly
seated.
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 (fig. 5-5D).
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.
mounting bracket to the power section (cut the nut at the
open slot in the threaded portion of the housing). Be careful
to avoid damage to the threads on the booster hub. Spread
the nut and remove it from the power section. Then remove
the m ounting bracket.
2. Remove the pedal rod boot (if equipped) by pulling
it off over the pedal rod eyelet.
3. Place Tool J-24569 around the pedal rod and resting
on the input rod end as shown in Figure 5-3E.
4. Place a punch (or similar tool) through the pedal rod
from the lower side of Tool J-24569. Push the punch on
through to rest on the higher side of the tool. Lift up on the
punch to shear the pedal rod retainer; remove the pedal rod.
5. Remove the rem nants of the rubber grom met from
the groove near the end of the pedal rod and from the groove
inside the input rod end.
6. W ith a small screwdriver, pry the plastic guide out
of the output push rod retainer. Disengage the tabs of the
spring retainer from the ledge inside the opening near the
m aster cylinder m ounting flange of the booster. Remove the
retainer and the piston return spring from the opening.
7. Pull straight out on the output push rod to remove
the push rod and push rod retainer from inside the booster
piston.
8. Press in on spool plug, and using a small screwdriver,
remove the snap ring from the housing bore.
9. Use pliers to remove the spool plug from the bore.
Remove the "O" ring seal from the plug; discard the "O"
ring. Remove the spool spring from the bore.
10. Place the booster cover in a vise equipped with soft
jawed devices. Using special socket J-25085, remove the five
screws that secure the booster housing to the cover.
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