27
MAINTENANCE
CAUTION
Overtightening the bolts can cause permanent
distortion of the clamp ring. Do Not exceed a
torque of 130 inch lbs. (14.7 Nm.)
Brake Chamber Removal
Disconnect the air line and the push rod yoke. Re-
move the nuts from the mounting studs. Remove the
air chamber.
Brake Chamber Disassembly
1. Clean the exterior of the brake chamber.
2. Put a mark on the parts so they can be reassembled
in the same relative positions.
3. Pull out the push rod and clamp the push rod in
the extended position with vise grip pliers.
NOTE: Tape the grips to prevent damage to the
push rod.
4. Remove the bolts from the clamp ring.
5. Spread the clamp ring and remove it.
CAUTION
Use care not to bend the clamp ring out of
shape.
6. Remove the pressure plate and diaphragm.
7. Remove the locknut and the yoke from the
push rod.
8. Release the grip on the push rod.
9. Remove the push rod and the spring.
Cleaning and Inspection of Parts
Clean the metal parts in a solvent. Inspect all the
parts for damage, wear or deterioration and replace
defective parts.
Brake Chamber Assembly
1. Stand the push rod assembly on a flat surface.
2. Put the return spring in position.
3. Place the non-pressure plate over the push rod.
4. Push the non-pressure plate down against the flat
surface. Hold it in place with vise grip pliers clamped
to the push rod.
NOTE: Tape the grips to prevent damage to the
push rod.
5. Place the clamp ring over the non-pressure plate
clamping surface.
6. Position the diaphragm in the pressure plate. As-
semble it with the non-pressure plate by working the
clamp ring over the pressure plate. Align all the marks
made during disassembly.
7. Draw the clamp lugs together. Start the clamp bolts
and nuts. Tighten the nuts to a maximum torque of 130
inch lbs. (14.7 Nm.).
CAUTION
Overtightening the bolts can cause permanent
distortion of the clamp ring.
Trailer ABS
Meritor WABCO ABS is an electronic system that
monitors and controls wheel speed during braking. The
system works with standard air brake systems.
ABS monitors wheel speed at all times and controls
braking during wheel lock situations. The system im-
proves vehicle stability and control by reducing wheel
lock during braking.
The ECU receives and processes signals from the
wheel speed sensors. When the ECU detects a wheel
lockup, the unit activates the appropriate modulator
valve, and the air pressure is controlled.
In the event of a malfunction in the system,, the
ABS in the affected wheel(s) is disabled; that wheel
still has normal brakes. The other wheels keep the
ABS function.
An ABS warning light lets drivers know the status
of the system.
For a complete description of diagnostic and main-
tenance procedures refer to Meritor WABCO Mainte-
nance Manual no. 33.
Installation
Place the brake chamber in the mounting bracket
and tighten the nuts on the studs. The drain hole must
be placed in the down position. Install the yoke and
the locknut on the push rod. Connect the push rod to
the slack adjuster with the yoke pin. Adjust the brakes.
Check the angle formed by the slack adjuster and the
push rod with the brakes applied. This angle must not
be less than 90
0
with the brakes adjusted. Turn the
yoke to obtain this angle. The angle must be the same
for all slack adjusters to obtain equal braking force at
all wheels.
