Bendix Commercial Vehicle Systems A2LS HYD DRUM BRAKES W/PARKING 2/08 - Manual (Page 10)

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FIGURE 20 - EXPANDER WEDGE
Note: Normal wear pressure marks should not be mistaken
for scoring. Some discoloration of the piston diameter
may be apparent; this is a normal result of brake
actuation over a long period of operation and should
be ignored.
4. Adjuster Shaft Assembly. Check for damaged threads.
Check the helix for burrs, corrosion, or missing teeth.
Check that the adjustment shaft turns easily in the piston
for the full length of the threads. Smooth with a fine
emery cloth or clean as required.
5. Manual Override. Check the teeth of the manual override
for wear or damage.
6. Housings. Examine the cylinder bores for signs of
corrosion, ridges, or score marks.
Note: Provided the cylinder bore surfaces are in perfect
condition, new seals, and if necessary, new pistons
may be used to rebuild the existing housings. If there
is any doubt as to the condition of the cylinders, new
wheel cylinder and expander units must be installed.
7. Backing Plate (dirtshield). Clean the backing plate with
a damp cloth and wire brush to remove any dirt or
corrosion from the surface of the backing plate.
IMPORTANT! PLEASE READ:
Do not use an air hose to blow dust out of the backing
plate (dirtshield). Never inhale dust from asbestos
brake lining. Asbestos dust, when inhaled, can be
dangerous to your health. Use a vacuum with a filter
to remove dust carefully from the backing plate and
drum.
8. Brake Drum. Inspect the drum for scores and cracks.
Refer to the vehicle service manual for inspection and
resurfacing procedures. Wipe drum clean with a cloth
dampened in Bendix Metal Clene. Do not contaminate
the braking surface of the drum with grease or brake
fluid.
REASSEMBLY
ASSEMBLE EXPANDER UNIT
Each Bendix drum brake repair kit contains a tube of
synthetic based grease that is recommended for all internal
expander parts (abutment tappet, roller tappet, piston, and
the wedge and roller assembly). This packaged grease, or
an approved substitute synthetic based grease, must be
used, and an adequate amount must be applied. Refer to
Figure 18 for identification of those parts being lubricated
with either the synthetic based grease or DOT 4 brake fluid
during assembly.
Use all of the parts supplied in the Bendix repair kit to replace
the old parts removed from the cylinders.
1. Clamp the expander housing in a bench vise with padded
jaws.
2. Thoroughly smear the wedge, cage, wedge seal and
roller assembly with the greased supplied. Fit the wedge
seal and retaining ring assembly as close to the cage
as possible.
3. Insert the wedge assembly into the expander housing
and retain with a new circlip.
4. Turn the expander housing in the vise to enable the
abutment tappet to be installed. Fit the dust boot to the
abutment tappet. Grease the inside of the dust boot and
the outside diameter and ramp face of the abutment
tappet with the grease supplied.
5. Insert the abutment tappet assembly into the housing
bore until it engages with the wedge cage and roller,
Figure 19. Install the dust boot to the end of the housing.
6. Smear the o-ring with the grease supplied and fit onto
the roller tappet/piston. Lubricate the piston seal with
new DOT 4 brake fluid and install the seal as shown in
Figure 20, with the lip of the seal facing outward toward
the pressure side. Liberally grease the ramp face and
INPUT TAPPET/PISTON
SEAL POSITION
O-RING
ROLLER TAPPET/
PISTON
ABUTMENT TAPPET
FIGURE 19 - EXPANDER TAPPET LOCATION
TAPPETS LOCATED OVER WEDGE,
CAGE & ROLLER ASSY.
STOP PIN