TM9-2330-207-14
Table 4-3. Organizational Troubleshooting Table - Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
1. BRAKES WILL NOT RELEASE (cont).
Step 5. Check for closed shutoff valves on towing vehicle.
Open valves if closed.
If valves are open, proceed to step 6.
Step 6. Check for weak or broken brake shoe tension spring.
Replace spring if defective. See para. 4-40.
2. NO BRAKES OR WEAK BRAKES.
Step 1. Check for closed shutoff valves on towing vehicle.
Open valves.
If valves are open, proceed to step 2.
Step 2. Check intervehicular air hoses for proper connection to towing vehicle.
Connect hoses properly.
If hoses are properly connected, proceed to step 3.
Step 3. Check for open drain cock in semitrailer air reservoir.
Close drain cock.
If drain cock closed, proceed to step 4.
Step 4. Check air pressure gage on towing vehicle for low air pressure indication.
Check air lines/connectors for restrictions and/or leakage.
Tighten connections; remove any restrictions from hoses and repair or replace
as necessary.
If air pressure gage indicates normal, proceed to step 5.
Step 5. Check for defective emergency relay valve (para. 4-39g).
If emergency relay valve is defective, replace (para. 4-47).
If emergency relay valve is not defective, proceed to step 6.
Step 6. Check for air in hydraulic brake system (all models except M127).
Bleed hydraulic brake system (para. 4-39b).
If no air in hydraulic brake system, proceed to step 7.
Step 7. Check for leaks in hydraulic system (all models except M127) (para. 4-39d).
Locate leak and tighten or replace broken flexible line or hydraulic line.
If not leaking, proceed to step 8.
Step 8. Check for grease on brake lining.
Replace brakeshoe (para. 4-40) and oil seal (para. 4-32), if defective.
If brake lining shows no grease, proceed to step 9.
