MERITOR-TP-9853

MERITOR WEDGE BRAKES

MAINTENANCE MANUAL NO. 4R

FEBRUARY 1995
MERITOR-TP-9853

  MERITOR-TP-9853 - Page 27 of 32

Section 6
Diagnostics
23
Section 6
Diagnostics
Table B:
Troubleshooting
Condition
Possible Causes
Correction
Brakes do not
apply.
1. Plugged or damaged air lines/valves.
2. Plungers seized in housing.
3. Push rod not connected to wedge.
4. Brakes not adjusted correctly.
1. Repair or replace air lines or
valves.
2. Inspect seals, lubricant and
plungers. Service as necessary.
3. Inspect and correct as needed.
4. Adjust brakes correctly.
Brakes do not
have enough
torque during
application.
1. Automatic adjusters not working.
2. Linings worn below minimum thickness,
damaged or missing.
3. Incorrect lining friction rating.
4. Air/spring chamber not threaded
completely into plunger housing.
5. Plungers seized in housing.
6. Grease or oil on linings.
7. Damaged diaphragm in air chamber.
8. Leaks in the air system.
9. Worn components.
1. Refer to “Automatic adjusters not
working.” on next page.
2. Replace linings.
3. Replace with correct lining.
4. Install chamber correctly.
5. Inspect seals, lubricant and
plungers. Service as necessary.
6. Clean or replace linings. Check
wheel seals for leaks.
7. Repair or replace air chamber.
8. Repair leaks.
9. Replace components.
One shoe lining
wears faster
than the other.
(RDA models
only.)
NOTE: The
leading shoe
lining normally
wears faster on
RSA models.
1. Wedge not correctly installed in air
chamber.
2. Brake shoes installed backwards.
3. Weak/damaged shoe return springs.
4. Wedge and roller assembly not correctly
installed in plunger ramp.
5. Lining friction ratings do not match.
6. One wedge roller is out of cage.
7. Grease or dirt on linings.
8. Loose, worn or missing shoe retaining
hardware.
9. Lightweight or out-of-round drums.
10. Automatic adjuster not operating
correctly.
11. Brakes are dragging.
12. Unequal pressure in air chambers.
13. Loose wheel bearings.
1. Install wedge and air chamber
correctly.
2. Install shoes correctly.
3. Replace return springs.
4. Install correctly.
5. Use matched linings.
6. Repair or replace wedge assembly.
7. Clean or replace linings. Check
wheel seal for leaks.
8. Repair or replace retaining
hardware.
9. Replace drums.
10. Refer to “Automatic adjusters not
working.” on next page.
11. Refer to “Brakes drag.” on next
page.
12. Determine cause and repair or
replace as needed.
13. Adjust wheel bearings correctly.


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