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3. INSPECT ADJUSTER MECHANISM
CAUTION: Follow all standard safety procedures
including, but not limited to, those on page 2 of this
service manual. See the vehicle manufacturer's
recommendations. When working on foundation
brakes, be sure that the vehicle is on level ground,
that the vehicle is parked by other means than the
foundation brakes, and that the wheels are chocked.
Aside from the normal maintenance schedule, this
Adjuster Check is also carried out when the Caliper
Movement Test (see Page 14) finds that the running
clearance is too small or too large.
The adjuster should then be checked as follows:
With the spring brake released (or caged), remove the
adjuster cap (37) using the tab, taking care not to move
the shear adapter (61). Note: One of two styles of adjuster
cover (stamped metal or plastic) may be used.
Although exploded view (Figure 25) shows the adjuster (23)
and shear adapter (61) separated, only turn the adjuster
with the shear adapter installed on the adjuster. Using a
box-end wrench or socket, turn the Shear Adapter (61)
counter-clockwise and listen for the sound of 2 or 3 clicks
as the mechanism increases the running clearance. Note:
Do not use an open-ended wrench as this may damage
the adapter.
CAUTION: Never turn the adjuster (23) without the
shear adapter (61) installed. The shear adapter is a
safety feature and is designed to prevent an excess
of torque being applied to the adjuster. The shear
adapter will fail (by breaking loose) if too much torque
is applied.
If the shear adapter fails, you may attempt a second time
with a new (unused) shear adapter. A second failure of the
shear adapter confirms that the adjustment mechanism is
seized and the caliper must be replaced.
With a box-end wrench (or socket) positioned so that it
can turn freely without coming into contact with parts of
the vehicle (See Figure 27) on the shear adapter, make
five to ten moderate applications of the brakes [at about
30 psi (2 Bar)]. For a normally functioning Bendix air disc
brake, the box-end wrench or socket should turn clockwise
in small increments. NOTE: As the number of applications
increases, the turning movement will decrease (as the
brake reaches its normal calibration point).
If the box-end wrench or socket does not: (a) turn at all,
or (b) turns only with the first application, or (c) turns
forward and backward with every application, the automatic
adjuster has failed and the caliper/carrier assembly must
be replaced.
FIGURE 24 - COVER REMOVAL
23 Adjuster
61 Adapter
37
Cap
Tab
FIGURE 25 - EXPLODED
VIEW OF ADJUSTER
AND ADAPTER
FIGURE 27 - ADJUSTMENT MECHANISM TEST
Bendix recommends installing a new adjuster cap (lightly
greased using white lithium-based grease) when returning
the air brake to service. Ensure that the tab is in the position
shown in Figure 26.
61
37
12
Inboard
Brake
Pad
12
Outboard
Brake Pad
37
Cap
Tab
FIGURE 26 - TAB
POSITION
15
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