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 295 of 1015

TM 9-2320-272-24-1

Table 2-4. Compressed

Air

and Brake System Troubleshooting (Contd).

MALFUNCTION

TEST OR INSPECTION

CORRECTIVE ACTION

Test 3. Check air pressure at brake pedal valve supply port (5).

Step 1.

Stop engine and open all drainvalves (1), in sequence shown, until brake system air

pressure is vented.

Step 2.

Close drainvalves (1).

Step 3.

Disconnect secondary pressure gauge air line (6) from pedal valve supply port (5).

Step 4.

Connect test gauge to supply port (5) of pedal valve (4).

Step 5.

Direct assistant to start engine and allow air system to build to normal operating

pressure.

Step 6.

Check test gauge reading.

a.

If test gauge reads normal operating pressure, repair or replace clogged air line (6) to

secondary air pressure gauge (3) on instrument panel.

b.

If test gauge reads no pressure, low pressure, or pressure is building slowly, perform

test 4.

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