Meritor Heavy-Duty P Series Maintenance Manual page 10

4 Prepare Parts for Assembly
WARNING
Do not operate the vehicle with the brake drum worn or
machined beyond the discard dimension indicated on the
drum. The brake system may not operate correctly. Damage to
components and serious personal injury can result.
CAUTION
Replace the brake drum if it is out-of-round. Do not turn or
rebore a brake drum, which decreases the strength and
capacity of the drum. Damage to components can result.
8. Use the following procedure to inspect the brake drums.
A. Check the brake drums for cracks, severe heat checking,
heat spotting, scoring, pitting and distortion. Replace
drums as required. Do not turn or rebore brake drums,
which decreases the strength and heat capacity of the
drum.
B. Measure the inside diameter of the drum in several
locations with a drum caliper or internal micrometer.
Figure 4.1.
If the diameter exceeds the specifications
supplied by the drum manufacturer: Replace the
drum.
Figure 4.1
Figure 4.1
9. Check the dust shields for wear and damage. Repair or replace
worn or damaged parts as necessary.
Slack Adjusters
1. If the slack adjuster has a quick connect clevis, check the gap
between the clevis and the collar.
If the gap exceeds 0.060-inch (1.52 mm): Replace the
clevis with a one-piece threaded clevis.
6 Meritor Maintenance Manual MM-0440 (Issued 09-04)
2.
You must disengage a pull pawl or remove a conventional pawl
before rotating the manual adjusting nut, or you will damage
the pawl teeth. A damaged pawl will not allow the slack
adjuster to automatically adjust brake clearance. Replace
damaged pawls before putting the vehicle in service.
NOTE: When you service an automatic slack adjuster with a
conventional pawl, replace the conventional pawl with a pull pawl.
3.
Figure 4.2
4000343a
You must turn the adjusting nut COUNTERCLOCKWISE when
you check gear torque on an automatic slack adjuster. If you
turn the adjusting nut incorrectly, you will damage the pawl
teeth. A damaged pawl will prevent the slack adjuster from
automatically adjusting the clearance between the linings and
drum. Damage to components can result.
4.
Check the clevis pins, clips and bushing in the slack adjuster
arm for wear and damage. Replace worn or damaged parts.
Check the bushing diameter to ensure it does not exceed
0.531-inch (13.5 mm).
If the bushing diameter exceeds 0.531-inch (13.5 mm):
Replace the bushing.
CAUTION
Disengage the pull pawl. Use a screwdriver or equivalent tool to
pry the pull pawl at least 1/32-inch (0.8 mm) to disengage the
teeth. Figure 4.2.
If the slack adjuster has a conventional pawl: Remove
the pawl. Figure 4.2.
PULL PAWL
CONVENTIONAL
PAWL
Figure 4.2
CAUTION
Check manual slack adjusters by rotating the adjustment nut of
the worm shaft to verify that the worm drive is free. Figure 4.3.
Replace the slack adjuster if the worm drive does not operate
correctly. Do NOT repair a manual slack adjuster.
PAWL
PRY UP
4000331b