Inspect the disc for minimum thickness, maximum
10. Install the brake disc into the brake housing.
width of the keyways, and warping. Check the disc for
11. Dip brake release unit packings from the
warpage by using a straightedge across the face of the
cure-date kit into the hydraulic fluid and install
disc. Instructions for straightening a warped disc can
on the brake release units.
be found in the applicable 03 manual. Replace a brake
12. Coat the piston of the release unit with a light
disc that is worn excessively.
coating of hydraulic fluid and install in the
When a brake disc keyway is worn excessively or
housing. Tighten the cylinder heads against the
elongated, inspect the brake disc drive keys within the
housing as specified in the MIM or the 03
wheel assembly for damage and security. Replace the
manual.
drive keys or the wheel if the damage exceeds the
13. Reinstall the inlet plug, bushing, and bleeder
limitations specified in the applicable MIM.
adapter into the housing. Use new packings that
The new linings are installed in the brake pistons,
have been dipped in hydraulic fluid.
the center carrier, and the backplate. The disc guide
14. Lockwire the cylinder heads, bleed the brake,
lining is riveted to the disc guide. The pistons are
and test the brake for leakage and proper
pushed back into the piston housing until a maximum
operation. Test pressure for this brake assembly
of 1/8 inch of lining is protruding beyond the housing.
is 1,100 psi. Hold the pressure for 2 minutes and
Assemble the brake on the axle flange, and torque all
check the assembly for leaks. Release and
attaching bolts as well as the four internal wrenching
reapply the pressure 10 times, and check for
bolts to the specifications provided in the MIM. The
proper brake operation and release of the discs.
fore and aft axle attaching nuts on the brake housing
Allow the brake to stand 2 minutes with pressure
must have their flat surface toward the setscrew on the
relieved to check for static fluid leakage.
final torque. The setscrews are tightened against the
flat surfaces to safety the nuts. Secure the four internal
On dual disc brakes, as well as some single disc
wrenching bolts with lockwire. The wheel is installed
brakes, the linings may be replaced without disturbing
and the shock strut lowered. Perform an operational
the brake hydraulic system. See figure 14-30. In this
check to verify proper operation. Specified steps
example, the shock strut is raised with a wheel jack
throughout the lining and disc replacement procedures
until the wheel is clear of the ground. The wheel is
and the final security of all attachments require quality
removed, and the four internal wrenching bolts that
assurance verification as indicated in the MIM.
attach the brake housing to the backplate are removed.
The two setscrews located at each side of the brake
Figure 14-31 shows the various steps involved in
housing are unscrewed enough to allow removal of the
replacing the piston seals and adjusting the return
seven axle flange attaching bolts. Make certain the
mechanism. The internal wrenching bolts holding the
brake assembly is supported before you remove the
cylinder housing to the carrier and backplate are
bolts, or damage to the brake hose could result.
removed (view A). The cylinder housing is placed
Remove the brake linings from the pistons, center
under a press, as illustrated in view B. Use the press
carrier, backplate, and disc guide. Riveted linings must
and the drive pin to force the adjusting pins through
be drilled. Snap-on or friction-fit linings can be easily
their grips and remove the pistons from the housing.
pried off with a common screwdriver. Remove dirt and
Make sure that the drive pin is centered on the adjusting
other foreign particles from the brake assembly
pin to prevent damaging the adjusting pin packings and
components by the use of low-pressure compressed air.
grips.
Wear safety eye protection during this operation.
Next, cut the lockwire on the locknut. Use the
Clean the external surfaces of the brake parts with
threaded bushing wrench, illustrated in view C, to
a cloth dampened with P-D-680 cleaning solvent.
remove the locknuts, bushings, spacers, and grips from
Replace any brake lining attaching buttons that are
the housing. Remove the spring retaining ring from
damaged. The housing, backplate, center carrier, and
within the piston, as shown in view D.
all bolts should be inspected for damage, cracks, or
With the linings still attached to the pistons,
leakage, as applicable. If the brake has hydraulic
support the pistons in a press. Use a 3-inch length of
leakage or if the housing, backplate, or center carrier is
7/8-inch steel tubing to force the guides to the bottom
damaged or cracked, the complete brake assembly
on the adjusting pins, as shown in view E. Hold the
should be replaced and turned in to supply for repair at
guides in the bottomed position and turn the threaded
the next higher level of maintenance.
14-30
