SECTION 4E
REAR DRUM BRAKES
SPECIFICATIONS
General Specifcations
|
Application
|
Millimeters
|
Inches
|
|
Brake Drums:
|
.
|
.
|
|
Inside Diameter
|
200.00
|
7.87
|
|
Maximum Revore Diameter
|
201.00
|
7.91
|
|
Out-to-Round
|
0.04
|
0.001
|
|
Wheel Cylinder Diameter:
|
.
|
.
|
|
Rear
|
20.64
|
0.81
|
Fastener Tightening Specifications
|
Application
|
N•m
|
Lb-Ft
|
Lb-In
|
|
Brake Line
|
16
|
12
|
-
|
|
Brake Wheel Hub/Backing Plate-to-Rear Axle Nuts
|
28
|
21
|
-
|
|
Rear Hub Caulking Nut
|
190
|
140
|
-
|
|
Wheel Cylinder-to-Backing Plate Bolt
|
8
|
-
|
71
|
DIAGNOSIS
Lining Inspection
- Raise and suitably support the vehicle.
- Remove the wheel. Refer to Section 2E, Tires and
Wheels.
- Release the parking brake.
- Remove the drum. Refer to " Drum"
in this section.
- Measure the lining thickness. The minimum lining
thickness is 0.5 mm (0.02 inch).
Caution : To avoid injury when servicing brake
parts, do not create dust by grinding or sanding the
brake linings or by cleaning the wheel brake parts
with a dry brush or with compressed air.
Important : Replace the shoe and lining assembly in
axle sets only.
- Install the drum, if removed.
- Install the wheel, if removed. Refer to Section 2E, Tires and
Wheels.
- Lower the vehicle.
Drums
Whenever brake drums are removed, they should be
thoroughly cleaned and inspected to see if the drums
are cracked, scored, deeply grooved, or beyond the
specified out-of-round limit.
- A cracked drum is unsafe for further service andmust
be replaced. Do not attempt to weld a cracked drum.
Smooth out any slight scores.
- Heavy or extensive scoring will cause excessive
brake lining wear and may require refinishing the
drum braking surface.
- If the brake linings are slightly worn but are still reusable
and the drum is grooved, polish the drum with a
fine emery cloth but do not refinish it. Eliminating all
grooves in the drum and smoothing the ridges on the
lining would remove too much metal and lining. If left
alone, the grooves and ridges match, and satisfactory
service can be obtained. If the brake linings need to
be replaced, refinish a grooved drum. A grooved
drum, used with a new lining, will not only wear the
lining, but also will make it difficult, if not impossible,
to obtain proper brake performance.
- An out-of-round drum makes accurate brake shoe
adjustment impossible and is likely to cause excessive
wear of other parts of the brake mechanism. An
out-of-round drum can also cause severe and irregular
tire tread wear, as well as a pulsating brake pedal.
- The extent to which a drum is worn or out of round
can be measured accurately with an inside micrometer
fitted with the proper extension rods. When measuring
a drum for wear or the extent to which it is out
of round, take measurements from the inside edge to
the outside edge of the machined surface at 90-degree
intervals around the circumference of the drum.
When the drum exceeds the specified out-of-round
limit, refinish the drum.
MAINTENANCE AND REPAIR
ON-VEHICLE SERVICE
Brake Adjustment
Removal Procedure
- Release the parking brake.
- Operate the brake at least 10 times until the jumping
of the adjustment spring on the adjustment nut can no
longer be heard on either brake drum.
- Raise and suitably support the vehicle.
- Remove the rear wheels. Refer to Section 2E, Tires and
Wheels.
Mark the position of the wheels relative
to the wheel hubs.
- Remove the caulking nut.
- Remove the brake drum.
- Using the rear brake adjuster nut, turn the adjuster
assembly in until there is a sufficient amount of drag
on the brake drum.
- Make sure that the parking brake lever stops are
against the edge of the shoe web. If they are not,
loosen the parking brake cable at the equalizer. Refer
to Section 4G, Parking Brake.
Installation Procedure
- Position
the rear brake drum. Fasten the rear hub
caulking nut.
Tighten
Tighten the one-piece rear hub caulking nut to 190 N•m
(140 lb-ft).
- Install the rear wheels. Refer to Section 2E, Tires and
Wheels.
Mark the position of the wheels relative
to the wheel hubs.
Important : The brake pedal must be operated more
than 10 times. When the clicking can no longer be
heard, the clearance between the brake shoe and drum
is adjusted.
- Apply the foot brake several times until the clicking of
the adjustment actuator can no longer be heard.
- Adjust the parking brake. Refer to Section 4G, Parking Brake.
Shoe and Lining
Removal Procedure
- Raise and suitably support the vehicle.
- Remove the rear wheels. Refer to Section 2E, Tires and
Wheels.
Mark the position of the wheels relative
to the wheel hubs.
- Mark the position of the wheels relative to the wheel
hub.
- Loosen the parking brake cable. Refer to Section 4G, Parking Brake.
Mark the position of the wheels relative
to the wheel hubs.
- Remove the drum caulkimg nut and the brake drum.
- Loosen the leading shoe hold-down return spring.
(The ABS braking system configuration is illustrated.)
- Disconnect the upper link of the connecting link spring
of the leading shoe to relieve tension on the
upper return spring.
- Remove the upper return spring and the adjuster.
- Unfasten the trailing shoe and lining assembly holddown
return spring.
- Disconnect the trailing shoe and lining assembly on
the right side.
- Detach the lower return spring.
Installation Procedure
- Measure the minimum brake lining thickness. Refer
to "Lining Inspection"
in this section.
- Clean the adjuster assembly and apply grease.
Notice :
If any parts are of questionable strength or quality
because of heat discoloration, excessive stress, or
wear, the shoes, the springs, or the adjuster assembly
should be replaced.
- Inspect the threads of the adjuster assembly for
smooth rotation.
- Install the trailing shoe and lining assembly with the
hold-down spring, the washer, and the pin.
- Make sure the parking brake cable is properly
routed and attached to the shoe lever.
Notice : Do not overstretch the lower return spring.
- Fasten the lower return spring on the shoe.
- Position the leading shoe and the adjuster assembly
against the backing plate.
- Fasten the lower return spring to the leading shoe.
- Install the adjuster assembly.
- Turn the adjuster in as far as possible.
- Position the spring clip toward the backing plate.
- Install the leading shoe with the hold-down spring.
- Attach the leading shoe upper link-spring connection,
which applies tension to the upper return
spring.
Notice : Do not overstretch the upper return spring.
- Install the upper return spring from the spring connecting
link to the brake shoe.
Notice : The nut must not lock firmly at the end of the
adjustment assembly.
- Before installing the brake drum, make sure the adjuster
assembly nut is drawn all the way to the stop.
- Install the
brake drum and fasten it with the rear hub caulking nut .
Tighten
Tighten the rear hub caulking nut to 190 N•m
(140 lb-ft).
- Install the rear wheels. Refer to Section 2E, Tires and Wheels.
- Adjust the rear wheel brakes. Refer to "Brake Adjustment"
in this section.
- Adjust the parking brake. Refer to Section 4G, Parking
Brake.
- Lower the vehicle.
Wheel Cylinder Assembly
Removal Procedure
- Raise and suitably support the vehicle.
- Remove the rear wheels. Refer to Section 2E, Tires and Wheels.
- Mark the position of the wheels relative to the wheel
hubs.
- Remove the brake drum.
- Remove the shoe and lining. Refer to "Shoe and Lining"
in this section.
- Clean dirt and foreign material from around the wheel
cylinder brake line inlet, the pilot, and the bolt.
- Disconnect the brake line from the wheel cylinder.
- Plug the opening in the brake line to prevent fluid loss
or contamination.
- Remove the wheel cylinder-to-backing plate bolt.
- Gently tap out the wheel cylinder from the backing
plate, using care not to damage the bleeder valve or
its cap.
Installation Procedure
- Install the wheel cylinder to the backing plate with the
wheel cylinder bolt.
Tighten
Tighten the wheel cylinder-to-backing plate bolt to
8 N•m (71 lb-in).
- Connect the brake line to the wheel cylinder.
Tighten
Tighten the brake line to 16 N•m (12 lb-ft)
- Install the shoe and lining, and the brake drum. Refer
to "Shoe and Lining"
in this section.
- Bleed the brakes. Refer to Section 4A, Hydraulic
Brakes.
Backing Plate
Removal Procedure
- Raise and suitably support the vehicle.
- Remove the brake shoe components, including complete
removal of the parking brake with the retainer.
Refer to "Shoe and Lining"
in this section and Section 4A, Hydraulic Brakes.
- Remove the nuts that secure the wheel hub assembly
to the backing plate.
- Remove the brake line and plug the opening in the
line to prevent fluid loss or contamination.
- Remove the wheel cylinder assembly. Refer to "Wheel Cylinder Assembly"
in this section.
- Remove the wheel hub assembly.
- In case of ABS brake, disconnect the cable that goes to the wheel speed sensor.
- Separate the backing plate and the gasket.
Installation Procedure
- Place the backing plate with a new gasket on the
wheel hub. (The ABS hub is shown.).
- Insert the complete wheel hub/backing plate assembly
into the rear axle plate. In case of ABS Brakes, Install the nuts and connect
the wheel speed sensor.
Tighten
Tighten the brake wheel hub/backing plate-to-rear
axle nuts to 28 N•m (21 lb-ft).
- Install the brake wheel cylinder assembly to the backing
plate. Refer to "Wheel Cylinder Assembly"
in this section.
- Connect the brake line.
Tighten
Tighten the brake line to 16 N•m (12 lb-ft).
- Install the brake components. Refer to "Shoe and Lining"
in this section.
- Install the parking brake cable with the retainer by attaching
the cable to the brake shoe lever. Refer to Section 4G, Parking
Brake.
- Bleed the brakes. Refer to Section 4A, Hydraulic
Brakes.
- Lower the vehicle.
UNIT REPAIR
Wheel Cylinder
Disassembly Procedure
- Remove the wheel cylinder assembly from the backing
plate. Refer to "Wheel Cylinder Assembly"
in this section.
- Twist off the boots, the pistons, and the seals from
each end of the wheel cylinder.
- Remove the spring assembly.
- Remove the bleeder cap and the bleeder valve.
Assembly Procedure
- Inspect the wheel cylinder bore and the pistons for
scoring, nicks, corrosion, and wear.
- Use a crocus cloth to polish out light corrosion in the
wheel cylinder bore.
Important : If the bore will not clean up with a crocus
cloth, replace the assembly.
- Clean all the parts in clean denatured alcohol or brake
fluid. Dry all the parts with unlubricated compressed
air and lubricate the new seals, the pistons, and the
wheel cylinder bore with clean brake fluid before assembly.
- Thinly coat all the parts except the dust caps with
brake cylinder fluid.
- Fasten the bleeder valve and the cap to the wheel cylinder.
- Attach to the wheel cylinder the spring assembly, followed
by the pistons, the seals, and the boots.
- Inspect the pistons for free movement.
- Install the wheel cylinder assembly. Refer to "Wheel Cylinder Assembly"
in this section.
GENERAL DESCRIPTION
AND SYSTEM OPERATION
Drum Brakes
This drum brake assembly is a leading/trailing shoe design.
Both brake shoes are held against the wheel cylinder
pistons by the lower return spring and the fixed
anchor plate near the lower return spring. When the
brakes are applied, the wheel cylinder pistons move
both shoes out to contact the drum. With forward wheel
rotation, the forward brake shoe will wrap into the drum
and become self-energized. With reverse wheel rotation,
the rear brake shoe is self-energized. Force from
the brake shoes is transferred to the anchor plate
through the backing plate to the axle flange. Adjustment
is automatic and occurs on any service brake application.
Do not switch the position of shoes that have been
in service, as this may render the self-adjustment feature
inoperative and result in increased pedal travel.
Notice : To avoid damaging the vehicle, observe the following
directions:
- Replace all the components included in the repair kits
used to service this drum brake.
- Do not use lubricated shop air on the brake parts, as
damage to the rubber components may result.
- If any hydraulic component is removed or disconnected,
it may be necessary to bleed all or part of the
braking system.
- Replace the shoe and linings in axle sets only.
- The torque values specified are for dry, unlubricated
fasteners.
- Perform service operations on a clean bench that is
free from all mineral oil materials.
