02-02-07
Brake System
02-02-07
ANTI-SKID CONTROL SYSTEM
RELEASE PAWL CAM PIN
RELEASE PAWL CAM LEVER
RELEASE CABLE
H
1636-
A
FIG. 10—Parking Brake Control Assembly
With Manual Release—Typical
power unit with mounting bracket is
riveted to the control assembly. The
vacuum actuated piston within the
unit is connected by a rod to the
upper end of the release lever (Fig. 9).
The lower end of the release lever ex-
tends out for alternate manual release
in the event of vacuum power failure
or for optional manual release at any
time.
Hoses connect the power unit and
the engine manifold to a vacuum re-
lease valve in the transmission neutral
safety switch.
The anti-skid control system con-
sists of three major components (Fig.
39).
Mechanically driven electromag-
netic sensors at each rear wheel; an
electronic control module mounted
under the glove box; a vacuum pow-
ered actuator attached to a bracket on
the inside of the right front frame rail
under the toe board.
The sensors consist of steel rings
having teeth on their outer diameters,
pressed on each axle shaft just out-
board of the wheel bearing. The teeth
rotate past corresponding teeth on the
inside diameter of stationary steel
rings mounted in the bearing retain-
ers.
Also mounted in the retainers, are
ring-shaped permanent magnets and
coils of wire. Two wires from each
sensor connect the sensors to the con-
trol module.
The control module consists of solid
state electronic components sealed in
a container. It is connected to the sen-
sors and to a solenoid on the actuator.
The actuator is similar to a vacuum
brake booster and consists of three
parts.
A chamber divided by a vacuum
suspended diaphragm; a hydraulic cyl-
inder connected to the diaphragm; and
a solenoid connected electrically to the
control module.
IN-VEHICLE ADJUSTMENTS AND REPAIRS
After any brake service work, ob-
tain a firm brake pedal before moving
the vehicle. Riding the brake pedal
(common on left foot application)
should be avoided when driving the
vehicle.
BRAKE SHOE ADJUSTMENTS—
DRUM BRAKES
The hydraulic drum brakes are
self-adjusting and require a manual
adjustment only after the brake shoes
have been relined, replaced, or when
the length of the adjusting screw has
been changed while performing some
other service operation. The manual
adjustment is performed with the
drums removed, using the tool and the
procedure detailed below.
When adjusting the rear brake
shoes,
check the parking brake cables
for proper adjustment. Make sure that
the equalizer operates freely.
To adjust the brake shoes:
1.
Use Rotunda Tool HRE 8650,
(Fig. 11) to determine the inside diam-
eter of the drum braking surface.
2.
Reverse the tool as shown in Fig.
11 and adjust the brake shoe diameter
to fit the gauge. Hold the automatic
adjusting lever out of engagement
while rotating the adjusting screw, to
prevent burring the screw slots. Make
sure the adjusting screw rotates freely.
If necessary, lubricate the adjusting
screw threads with a thin, uniform
coating of MIC-100-A.
3.
Rotate Tool HRE 8650 around
the brake shoes to be sure of the set-
ting.
4.
Apply a small quantity of high
temperature grease to the points
where the shoes contact the backing
plate, being careful not to get the lu-
bricant on the linings.
5. Install the drums. Install Tinner-
man nuts and tighten securely.
6. Install the wheels on the drums
and tighten the nuts to specification.
7.
Complete the adjustment by
applying the brakes several times with
a minimum of 50 lbs pressure on the
pedal while backing the vehicle. After
each stop the vehicle must be moved
forward.
8. After the brake shoes have been
properly adjusted, check the operation
of the brakes by making several stops
while operating in a forward direction.
WHEEL CYLINDER REPAIR-
DRUM BRAKE
Wheel cylinders should not be di-
sassembled unless they are leaking or
unless new cups and boots are to be
installed. It is not necessary to remove
the brake cylinder from the backing
plate to disassemble, inspect, or hone
and overhaul the cylinder. Removal is
necessary only when the cylinder is
damaged or scored beyond repair.procarmanuals.com
