AIR BRAKE SYSTEM TROUBLESHOOTING

TM 9-2320-285-24-1

12-47. AIR BRAKE SYSTEM TROUBLESHOOTING

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

RAPID PRESSURE DROP AFTER ENGINE IS SHUT DOWN (BRAKES RELEASED)

Step 1.

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

period.

a. If AIR PRESS gage reading drops less than 2 psi per minute, air system leakage is within limits.

b. If AIR PRESS gage reading drops more than 2 psi per minute, go to step 2 below.

Step 2.

Check for open drain cock on service air tank.

a. If drain cock is open, close it fully.

b. If drain cock is closed fully, go to step 3 below.

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 lines and fittings are not leaking air, notify direct support maintenance.

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

Step 1.

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

period.

a. If AIR PRESS gage reading drops more than 2 psi per minute, go to Malfunction 1, step 2,

above.

b. If AIR PRESS gage reading drops less than 2 psi per minute, go to step 2 below.

Step 2.

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

minute period.

a. If AIR PRESS gage reading drops less than 3 psi per minute, air system leakage is within limits.

b. If AIR PRESS gage reading drops more than 3 psi per minute. Go to step 3 below.

2-533