TM 9-2330-294-14
Table 4-4. Troubleshooting Air System Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
13. BRAKES OVERHEAT
Step 1. Check for insufficient lining to drum clearance (para 4-30b(3)).
Adjust brakes (para 4-30b (3)). If this fails inspect, repair or replace automatic adjuster
Step 2. Pull hub(s) and drum(s) (para 4-60) and visually inspect brake mechanism. Apply brake and
observe shoe movement. Shoes should expand and return smoothly.
Replace broken return spring (para 4-31). If shoe action is still not smooth and free
clean brake mechanism parts and reassemble.
14. UNEVEN BRAKES
Step 1. See malfunction 4, step 1.
Adjust brakes (para 4-30b). If this fails inspect, repair or replace automatic adjuster
Step 2. See malfunction 4, step 2.
Replace damaged or plugged air line (para 4-39).
Step 3. See malfunction 4, step 3.
Clean, repair or replace brake mechanism parts (para 4-30 through 4.35).
Step 4. See malfunction 9, step 4.
Replace relay valve (para 4-42)
15. HARD PULLING BRAKES
Step 1. See malfunction 4, step 1.
Adjust brakes ( para 4-30b). If this fails inspect, repair or replace automatic adjuster
Step 2. See malfunction 4, step 2.
Replace damaged or plugged air line (para 4-39).
Step 3. See malfunction 4, step 3.
Clean, repair or replace brake mechanism part (para 4-30 through 4-35).
Step 4. See malfunction 9, step 4.
Replace relay valve (para 4-42).
16. FAIL-SAFE NOT HOLDING
Step 1. Check to see if the power springs are released.
CAUTION
If springs are already fully released, the release bolt may be against its stop so do not use heavy
force if the bolt will not turn. Excessive force can strip the release bolt.
Turn release bolt counterclockwise until a stop is felt (para 4-30d).
Step 2. Check for excessive drum to lining clearance (para 4-30b ).
Adjust brakes (para 4-30b). If this fails inspect, repair, or replace plunger housing
assembly (para 4-35).
Step 3. Check for jammed brake actuators on wheel ends or mud or ice in mechanism.
Expose brakes to warmth. Clean parts of mud and dry all parts.
Step 4. Turn release bolt clockwise. Lack of resistance indicates broken spring or stripped bolt.
If bolt turns clockwise after 25 turns are made, bolt threads are stripped.
CAUTION
Do not force bolt. A stop is built into the fail-safe, and the bolt can be stripped if turned past this
stop .
Replace fail-safe (para 4-32).
17. NO BRAKES WILL RELEASE (SEMITRAILER COUPLED TO TOWING VEHICLE)
Check for defective emergency relay valve (para 4-37f ),
Replace relay valve (para 4-42).
18. BRAKES WILL NOT RELEASE ON SINGLE WHEEL
Step 1. Visually inspect air line in immediate area of locked wheel for dents or breaks. Manually
compress fail-safe; if wheels become free obstruction in air supply is indicated.
Replace damaged or plugged tubing (para 4-39).
Change 1
