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2 - 6
GROUP 2-BRAKES
kit is used install all of the parts sup-
plied in the kit.
BRAKE DRUM REFINISHING
Minor scores on a brake drum can
be removed with fine emery cloth,
provided the emery
is thoroughly
cleaned off the d r u m after the opera-
tion.
A badly scored, rough, or out-of-
round drum should be ground or
turned on a d r u m lathe. D o not re-
m o v e any more material from the
d r u m than is necessary to provide a
smooth surface for the brake shoe
contact.
T h e refinished
diameter
should not be more than 0.060 inch
oversize. For original brake drum
sizes, see Part 2-4 Specifications.
If the diameter of the drum is less
than 0.030 inch oversize after refin-
ishing. install standard linings on the
brake assemblies. If the diameter is
over 0.030 inch, install oversize or
shimmed linings.
BRAKE SHOE RELINING
1. Remove the rivets and remove
the old lining.
2. Clean the shoe thoroughly with
cleaning fluid, especially the rim sur-
face. Wipe the shoe dry and remove
all burrs or rough spots from the
shoe.
3. Check the inside diameter of
the brake drum. If the diameter is
less than 0.030 inch oversize, install
standard linings. If the diameter i s
0.030-0.060 inch
oversize, install
oversize or shimmed linings.
4. Position the n e w lining on the
shoe and install new rivets, beginning
with the rivet holes near the center of
the shoe. O n some trucks, the pri-
mary lining i s shorter than the sec-
ondary lining. If this condition exists,
position the shorter (primary) lining
to line up with the heel end of the
shoe. D o not let oil or grease touch
the brake lining. If a brake lining kit
is used to replace the worn linings,
install all the parts supplied in the kit.
5. Check the clearance between
the lining and shoe rim. T h e lining
must seat snugly against the rim with
not more than 0.005-inch separation
REAR AXLE HOUSING
BRAKE HOSE
VENT
CONNECTOR
BRAKE TUBES
H1018-B
FIG. 5—Rear Brake Tube
Connector
midway between any two rivets. If
only the linings are replaced on duo-
servo single anchor brakes with fixed
anchor pins, the brake linings must
be c a m ground 0.010 inch at the ends
after the linings are riveted to the
brake shoe.
HYDRAULIC LINE
REPLACEMENT
Steel tubing is used throughout the
brake system with the exception of
the flexible hoses at the front wheels
and at the rear axle housing brake
tube connector (Fig. 5).
W h e n connecting a replacement
hose to the rear tube connector or
to either front brake cylinder, always
use n e w gaskets. W h e n connecting
tubes to the rear connector, hoses,
or rear brake cylinders, tighten the
pipe fitting nut to the specified
torque with tool 1112-144.
If a section of the brake tubing
becomes damaged, the entire section
should be replaced with tubing of
the same size, shape, and length.
Copper tubing should not be used
in a hydraulic system.
The brake tubing should be dou-
ble flared to provide a leakproof
connection, and should be cleaned
with denatured alcohol before instal-
lation.
W h e n installing a n e w brake hose,
position the hose so as to avoid con-
tact with other chassis parts.
CLEANING AND INSPECTION
brake assemblies, remove the cover
with the brake cylinder.
4. Position the brake cylinder on
the carrier plate and install the re-
taining bolts and lockwashers. O n the
two-cylinder brake assemblies, install
the cover with the brake cylinder.
5. Install a new gasket on the
brake line fitting and connect the line
to the brake cylinder(s).
6. Install the brake shoes and the
connecting links between the shoes
and cylinder. Install the d r u m and
the wheel.
REPAIR
1. With
the wheel cylinder re-
moved, remove the rubber boots from
the end(s) of the brake cylinder. Re-
m o v e the piston(s), cup(s), and piston
return spring from the cylinder (Fig.
3 or 4).
2. R e m o v e the bleeder screw from
the cylinder.
3. Coat all brake cylinder parts
with clean heavy-duty brake fluid.
4. Install the bleeder screw (Fig.
3 or 4) in the brake cylinder.
5. Place the piston return spring,
cup(s) and piston(s) in the cylinder
bore, and clamp the brake cylinder
pistons against the end(s) of the cyl-
inder. W h e n a brake cylinder repair
PISTON
RETURN
CUP
BOOT
FIG. 3—Duo-Servo Brake
Cylinder
PISTON
RETURN
CYLINDER
FIG. 4—Uni-Servo Brake
Cylinder
BRAKE CYLINDER
1. Clean all brake cylinder parts
in clean denatured alcohol. Inspect
all parts for wear or damage. Check
the cylinder bore for rust, scores, or
other damage. B e sure that the bleed-
er screw passage is clean and open.
Replace all parts that are worn or
damaged. W h e n a brake cylinder re-
pair kit is used, install all of the
parts supplied in the kit.
2. If dirt is found in any part of
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