RAPID PRESSURE DROP AFTER ENGINE IS SHUT DOWN (BRAKES APPLIED) (Cont)

TM 9-2320-285-24-1

2-47.

AIR BRAKE SYSTEM TROUBLESHOOTING (CONT)

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

2. RAPID PRESSURE DROP AFTER ENGINE IS SHUT DOWN (BRAKES APPLIED) (Cont)

Step 3.

Check air brake system lines and fittings for air leaks.

a. If line is leaking air, replace (para 2-51a). If fitting is leaking air, tighten. If fitting leaks after

tightening, replace (para 2-51a).

b. If air leaks are not seen, notify direct support maintenance.

3. PRESSURE BUILDS UP SLOWLY

Step 1.

Open drain cock on service air tank to relieve system pressure to zero; then close drain cock.

Note and record time; then start engine and operate at 1200 rpm.

Note and record time when AIR PRESS gage indicates 90 psi.

a. If elapsed time is 5 minutes or less, no further action required.

b. If elapsed time is more than 5 minutes, go to step 2 below.

Step 2.

Stop engine, open engine hood, and check fan and air compressor belts for proper tension.

Depress belts midway between fan pulley and crankshaft pulley.

Belts should deflect 1/2 inch with moderate thumb pressure.

a. If belts do not deflect 1/2 inch, adjust tension (para 2-15d).

b. If belts deflect approximately 1/2 inch, go to step 3 below.

Step 3.

With engine off and brake pedal released, record drop in AIR PRESS gage reading during 1-minute

period.

a. If reading drops more than 2 psi per minute, refer to Malfunction 1, step 2, above.

b. If reading drops less than 2 psi per minute, notify direct support maintenance.

4. PRESSURE WON'T BUILD UP TO NORMAL

Troubleshoot AIR PRESS gage (para 2-83).

a. If AIR PRESS gage is defective, replace (para 2-87b).

b. If AIR PRESS gage is okay, go to Malfunction 3, step 1, above.

2-534