TM 9-2330-294-14
Table 4-4. Troubleshooting Air System -- Continued
TEST OR INSPECTION
CORRECTIVE ACTION
2. NO BRAKE RESPONSE ON FRONT TANDEM ONLY, OR
ON REAR TANDEM ONLY-Continued
Step 3. Check for defective emergency relay valve on axle without brakes (para 4-37f).
3. NO BRAKES ON ONE TRAILER AXLE ONLY
Visually inspect air line between emergency relay valve and brake chambers on affected axle
for dents or breaks. Cautiously loosen line fitting near one brake chamber while brakes are
applied and listen for escaping air; no air indicates plugged line.
4. NO BRAKE RESPONSE AT ONE WHEEL ONLY
Step 1. Check for excessive drum to lining clearance (pare 4-30b).
Adjust brakes (para 4-30b). If this fails inspect, repair or replace plunger
Step 2. Visually inspect air line between emergency relay valve and brake chambers for breaks or
dents. Cautiously loosen line fitting near one brake chamber while brakes are applied and
listen for escaping air; no air indicates plugged line.
Step 3. Check air chamber for punctured diaphragm (para 4-32a). Manually compress fail-safe
(para 4-30d) and remove, inspect
and clean
air chamber and wedge assembly. Pull hub and
drum (para 4-60) and visually inspect mechanism. Assure brake shoe return springs
are properly engaged. Inspect and service plungers.
Clean, repair or replace brake mechanism parts (para 4-30 through 4-35).
5. ALL TRAILER BRAKES WEAK
Step 1. Check for ice or mud in brake mechanism. Pu1l hub(s) and drum(s) (para 4-60) and visually
inspect brake parts.
Expose brakes to warmth. Clean parts of mud and dry all parts.
Step 2. Pull hub(s) and drum(s) (para 4-60) and visually inspect for worn out brake lining (para 4-
31).
Step 3. Check for excessive lining to drum clearance (para 4-30b).
Adjust brakes (para 4-30b). If this fails inspect, repair or replace plunger housing
6. WEAK BRAKES AT ONE OR MORE WHEEL LOCATIONS, BUT NOT ALL
Step 1. Check for ice or mud in brake mechanism. Pull hub(s) and drum(s) (para 4-60) and visually
inspect brake parts.
Expose brakes to warmth. Clean parts of mud and dry all parts.
Step 2. Pull hub(s) and drum(s) (para 4-60) and visually inspect for worn out brake lining (para 4-
31).
Step 3. Check for excessive lining to drum clearance (para 4-30b).
Adjust brakes (para 4-30b). If this fails inspect, repair or replace plunger housing
Step 4. Pull hub(s) and drum(s) (para 4-60) and visually inspect for grease on brake lining.
Step 5. Pull hub(s) and drum(s) (para 4-60). Activate brakes and observe shoe and plunger
movement. One or both wedge assemblies on wheel(s) could be jammed.
Depressureize air system. Compress fail-safe(s) manually (para 4-30d). Remove air
chambers (para 4-33) and remove, inspect, clean or replace plunger housing assembly
Step 6. Check to see if one or both brake air chambers are leaking. Air leak should be audible if
very large. Apply and hold brake; leakage in area of brake chambers, other than initial
venting of air caused by movement of diaphragm, is not permissible.
4-10