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2-6
PART
2-2
BRAKE SYSTEM
Section
Page
1
Description
and
Operation
2-6
2 In-Car
Adjustments
and
Repairs
2-9
Section
3 Removal
and
Installation
4 Major Repair
Operations
Page
.2-14
.2-16
DESCRIPTION AND OPERATION
HYDRAULIC SELF-ADJUSTING
BRAKE SYSTEM
The hydraulic brake
system
em
ploys
single
anchor,
internal
expand
ing
and
self-adjusting brake
assem
blies,
and
is
powered
by
a
vacuum
booster.
The
master cylinder converts phys
ical
force from
the
brake
pedal
and
booster
into
hydraulic
pressure
against
the
pistons
in
the
wheel cyl
inders. The
wheel
cylinder
pistons
in
turn
convert
hydraulic
pressure
back
into
physical
force
at
the
brake
shoes.
The self-adjusting brake
mechan
ism
consists of
a
cable,
cable
guide,
adjusting
lever,
adjuster
spring,
and
adjuster
screw
(Fig. 1). The
cable
is hooked
over
the
anchor pin at
the
top
and
is
connected
to
the
lever
at
the
bottom.
The
cable
is
con
nected
to the
secondary brake
shoe
by
means
of
the
cable
guide.
The
adjuster
spring
is
hooked
to
the
primary brake
shoe and
to the
lever.
The
automatic
adjuster
operates
only
when
the
brakes
are
applied
while
the
car
is
moving
rearward
and
only
when
the
secondary
shoe
is free
to
move
toward
the
drum
beyond
a
predetermined
point.
With
the
car
moving
rearward
and
the
brakes
applied,
the
"wrap
around"
action
of
the
shoes
follow
ing
the
drum
forces
the
upper
end
of
the
primary
shoe
against
the
anchor pin.
The
action
of
the
wheel
cylinder
moves
the
upper
end
of
the
secondary
shoe
away from
the
anchor
pin.
The
movement
of
the
secondary
shoe
causes
the
cable
to
pull
the
adjusting
lever
upward
and
against
the
end
of
a
tooth
on
the
adjusting
screw
star
wheel.
The up
ward
travel
of
the
lever increases
as
lining
wear
increases.
When
the
PARKING
BRAKE
LEVER
RETAINING CLIP
WASHER
PARKING BRAKE
LEVER
ANCHOR
PIN
PLATE
ANCHOR
PIN
,
ANTI-RATTLE
CLIP
FOREWARD
PRIMARY
SHOE-TO-ANCHOR
SPRING
SHOE
HOLD-DOWN
SPRINGS
CABLE
HOOK
PARKING
BRAKE
CABLE
HOUSING
RETAINER
SHOE
HOLD-DOWN
SPRINGS
PRIMARY
SHOE
AUTOMATIC
ADJUSTER
SPRING
PARKING
BRAKE
CABLE
AND
HOUSING
PIVOT NUT
HI
1 54-C
FIG. 1
-Self-Adjusting
Brake Assemblies
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