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PART 2-1
-GENERAL
BRAKE SERVICE
25
MASTER CYLINDER
PUSH
ROD ADJUSTMENT
The
push
rod
is designed
with
a
self-locking
adjustment
screw
to
pro
vide
the
correct
relationship between
the
booster
piston
and
the
master
cylinder
piston.
The
adjustment
screw
is
set
to the
correct
height
at
the time
of
original
assembly
of
the
power
unit.
Under
normal
service
the
adjustment screw
does
not re
quire
any
further
attention provid
ing
the
push rod
assembly
remains
in
the
original unit.
However,
when
a new push rod
is
used or
the
push
rod
assembly is
transferred
to
an
other
unit,
the
distance
from
the
end
of
the
adjustment
screw
to
the
mounting
surface
of
the
booster
body
should
be
rechecked either with
a
micrometer
depth
gauge
to
a
di
mension of
0.990-0.995
inch,
or
with
a
height
gauge
as
shown
in Fig. 2.
The
details
for
making
a
height
gauge
are
given
in Fig. 3.
To
adjust
the
push
rod,
hold
the
serrated
end
of
the
rod
with
cross-
milled pliers and
turn the
adjustment
screw
in
to
shorten,
or
out
to
lengthen.
After assembly
of
the
master cyl
inder
to
the
power
section, the
piston
cup in
the
hydraulic
cylinder should
just
clear
the
compensating
port
hole
when
the
unit
is in
the
fully
released
position.
This
can
be
checked
by
placing
a
few drops
of
brake fluid
over
the
compensating
port
and
ap
plying light
air pressure
to the
output
port
of
the
master
cylinder.
If
air
bubbles
appear, the
port
is
open.
If
the
primary
piston
cup
overlaps
the
compensating
port, there
will
be
no
flow
of air
through
the
compensating
port.
If
this
condition
exists, the
ad
justment
screw should
be
turned
into
the
push rod a
slight amount
or until
the
compensating
port
is
open.
HYDRAULIC
SYSTEM BLEEDING
When any
part
of
the
hydraulic
system
has
been
disconnected
for
repair
or
replacement,
ajr
may
get
into
the
lines
and cause
spongy
pedal
action.
Bleed
the
hydraulic
system
after
it has
been properly
connected
ADJUSTMENT
SCREW
Push Rod
Gauge
#15
OR
#16 U.S.S. GAUG
E SHEET
H
STEEL
-
'
~
l3/4"
t
0.990"
0.995"
1
*1-1/16'S-
-%"*
H1087-C
H1086-A
FIG. 2
-Push
Rod Adjustment
FIG. 3-Push Rod Guage
Dimensions
to
be
sure
that
all
air
is
expelled
from
the
brake
cylinders,
disc
brake
calipers,
and
lines.
The hydraulic
system can
be
bled
manually
or
with
pressure
bleeding
equipment.
With disc
brakes,
more
pumping
of
the
pedal
is
required
and
more
frequent
checking
of
the
master
cylinder
may
be
necessary
while
bleeding.
Remove
the
front
wheel
and
tire
assemblies
in
order
to
gain
access
to
the
bleeder fittings
on
the
disc
brake
calipers.
MANUAL
BLEEDING
Bleed
the
longest lines
first.
Keep
the
master
cylinder
reservoir
filled
with
new
SAE
70R3-Wagner
2 IB
(301)
brake
fluid
during
the
bleeding
operation.
Never
use
brake
fluid
which
has
been drained from
the
hydraulic
system.
1.
Position
a
bent
%-inch
box
wrench on
the
bleeder
fitting
on
the
right rear
brake
wheel
cylinder
(Fig.
4). Attach
a
rubber
drain
tube to
the
bleeder fitting. The
end
of
the
tube
should
fit
snugly
around
the
bleeder fitting.
2. Submerge
the
free
end
of
the
tube
in
a
container
partially
filled
with
clean
brake
fluid,
and
loosen
the
bleeder
fitting
approximately
Va
turn.
3. Push
the
brake
pedal
down
slowly
thru
its full
travel.
Close
the
bleeder
fitting,
then
return
the
pedal
to the
fully-released
position.
Repeat
this
operation until
air
bubbles
cease
to
appear
at
the
submerged
end
of
the tube.
4. When
the
fluid
is
completely
free
of air
bubbles,
close
the
bleeder
fitting
and remove
the
drain
tube.
5. Repeat
this
procedure
on
the
brake
cylinders
or
disc
calipers
at
each
wheel
in
order:
left
rear,
right
front,
and
left
front.
Refill
the
master
cylinder
reservoir
after
each
brake
cylinder
is
bled
and
when
the
bleeding
operation
is
completed.
The
fluid
level
should
be
within
%
inch
of
the
top
of
the
reservoir.
The
diaphragm-type
gasket
should
be
properly
positioned
in
the
reservoir
cap
before
the
cap
is
installed.
6. Be
sure
that
the
front
brake
pistons
are
returned
to
their
normal
positions
and
that the
shoe
and
lin
ing
assemblies
are
properly
seated.
7. Before
driving
the
car,
check
the
operation
of
the
brakes
and
be
sure
that
a
firm
pedal
is
obtained.
PRESSURE BLEEDING
Bleed
the
longest
lines first.
Never
use
brake
fluid
which
has
been
drained from
the
hydraulic
system.
The bleeder
tank
should
contain
enough
new
heavy-duty
brake
fluid
to
complete
the
bleeding
operation,
and
it
should
be
charged with
10-30
pounds
of air
pressure.
1. Clean
all
dirt from
the
master
cylinder
reservoir
cap.
2. Remove
the
master
cylinder
reservoir
cap,
install
an adapter
cap
to
the
reservoir,
and
attach
the
bleeder
tank
hose
to the
fitting
on
the
adapter cap.
An
adapter
cap
can
be
fabricated
by
cutting
a
hole in
the
center of a
reservoir
cap
and
soldering
a
fitting
at
the
hole. The
adapter
cap
must
be
securely
seated and
completely
sealed
on
the
master
cylinder
or
leakage
will
occur.
3. Position
a
%-inch box
wrench
on
the
bleeder
fitting
on
the
right
rear
brake
wheel
cylinder
(Fig. 4).
Attach
a
rubber
drain
tube to
the
bleeder fitting. The
end
of
the tube
should
fit
snugly
around
the
bleed
er
fitting.
4. Open
the
valve
on
the
bleeder
tank to
admit pressurized
brake fluid
to the
master cylinder reservoir.
5. Submerge
the
free
end
of
the
tube
in
a
container
partially
filled
with
clean
brake
fluid,
and
loosen
the
bleeder fitting.
6. When
air
bubbles
cease
to
ap
pear
in
the
fluid
at
the
submerged
APPROXIMATELY
45'
HI
300
A
FIG. 4-Brake Bleeder
Wrench
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