TM 9-2330-294-14
Table 4-4. Troubleshooting Air System Continued
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
7. SLOW BRAKE APPLICATION - ALL SEMITRAILER BRAKES
Step 1. Check for damaged service air line.
Replace damaged air line (para 4-39).
Step 2. Disconnect service air line (fig. 4-27 or 4-28) at emergency relay valves that serves mal-
functioning brakes.
Depress and release towing vehicle brake pedal. Air should escape with brake application
and immediately stop flowing when pedal is released. Any other response indicates plugged
line.
Replace plugged air line (para 4-39).
Step 3. Visually inspect air line connecting emergency relay valves to reservoir for dents or breaks.
Cautiously loosen fitting a few threads at emergency relay valve. Air should escape;
no air indicates plugged line.
Replace damaged or plugged air line (para 4-39).
8. SLOW B R A K E R E L E A S E - A L L S E M I T R A I L E R B R A K E S
Step 1. See malfunction 7, step 1.
Replace damage air line (para 4-39).
Step 2. See malfunction 7, step 2.
Replace plugged air line (para 4-39).
9. SLOW BRAKE APPLICATION ON ONE OR THE OTHER SEMITRAILER TANDEM
Step 1. See malfunction 7, step 1.
Replace damagd air line (para 4-39).
Step 3. See malfunction 7, step 2.
Replace plugged air line (para 4-39).
Step 3. See malfunction 7, step 3.
Replace damaged or plugged air line (para 4-39).
step 4. Check for defective emergency relay valve (para 4-37f ).
Replace relay valve (para 4-42).
10. SLOW BRAKE RELEASE ON ONE OR THE OTHER SEMITRAILER TANDEM
Step 1. See malfunction 7, step 1.
Replace damage air line (para 4-39).
Step 2. See malfunction 7, step 2.
Replace plugged air line (para 4-39).
Step 3. See malfunction 9, step 4.
Replace relay valve (para 4-42).
11. SLOW BRAKE APPLICATION OR RELEASE ON ONE AXLE ONLY
Step 1. See malfunction 6, step 1.
Expose brakes to warmth. Clean parts of mud and dry all parts.
Step 2. See malfunction 4, step 2.
Replace damaged or plugged air line (para 4-39).
Step 3. See malfunction 6, step 6.
Replace brake air chamber (para 4-33).
12. GRABBING BRAKES
Step 1. Pull hub(s) and drum(s) (para 4-60) and visually inspect for grease on brake linings or
damage. Check brake drum for scoring or cracking.
Replace shoe and lining assembly (para 4-31). Replace grease seals on axle ends if
grease is found on linings (para 4-60). Replace drum (para 4-60).
Step 2. See malfunction 9, step 4.
Replace relay valve (para 4-42).
Step 3. Pull hub(s) and drum(s) (para 4-60) and inspect for loose or damaged wheel bearings.
Adjust or replace wheel bearings (para 4-60).
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