TM-9-2320-272-24-1

TRUCK, 5-TON, 6X6, M939, M939A1, AND M939A2 SERIES TRUCKS (DIESEL)

TECHNICAL MANUAL; UNIT, DIRECT SUPPORT, AND GENERAL SUPPORT MAINTENANCE MANUAL; VOLUME 1 OF 4

JUNE 1998

TM-9-2320-272-24-1 - Page 267 of 1015

TM 9-2320-272-24-1

Table 2-4. Compressed Air and Brake System Troubleshooting.

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

PARKING BRAKE

1. PARKING BRAKE DOES NOT HOLD VEHICLE ON GRADE

Test 1. Check parking brake adjustment.

a. Release spring brakes (TM 9-2320-272-10).

b.

Turn knob (1) on parking brake lever (2) clockwise to increase braking action.

c.

If adjustment does not correct malfunction, perform test 2.

Test 2. Inspect parking brake cable (3) for binding or breaks.

a.

Replace cable (3) if binding or broken (para. 3-175).

b.

If cable (3) is not damaged, perform test 3.

Test 3. Inspect parking brakeshoes (6) for wear.

a.

Push brakeshoe lever (4) clockwise by hand and measure brakeshoe lever travel.

b.

If travel is more than 2 in. (5) mm), replace parking brakeshoes (6) (para. 3-176).

Test 4. Inspect for broken or faulty actuating plate (7).

a.

Move brakeshoe lever (4) back and forth. Observe operation of brakeshoe lever (4),

spring (5), and actuating plate (7).

b. If actuating mechanism is defective, notify DS maintenance.

c.

If actuating mechanism is serviceable, perform malfunction 19.

END OF TESTING!

2. PARKING BRAKE DRAGS, AS INDICATED BY SMOKING OR BURNING SMELL

Ensure parking brake lever (2) is not partially engaged.

a. Fully release parking brake.

b.

If parking brake still drags, perform malfunction 1, tests 1, 2, and 4.

END OF TESTING!

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