TM-9-2320-272-23-1

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

TECHNICAL MANUAL; FIELD MAINTENANCE MANUAL; VOLUME 1 OF 5

SEPTEMBER 2012

TM-9-2320-272-23-1 - Page 1030 of 1313

INSUFFICIENT BRAKES (VEHICLE STOPPING DISTANCE TOO LONG, NO APPARENT AIR SYSTEM

FAILURE WITH GAUGES AT NORMAL OPERATING PRESSURE, WARNING BUZZER NOT SOUNDING) -

Continued

e.

Remove plug from service brake pedal valve primary air system delivery port. Refer to point to point

schematics.

f.

Connect pressure gauge to primary air system delivery port.

g.

Assistant starts engine and runs to build air supply to normal operating pressure.

h.

Assistant fully applies and holds service brakes.

i.

Monitor air pressure on pressure gauge.

j.

Pressure gauge should read 90 to 130 psi.

CONDITION/INDICATION

IS PROPER AIR PRESSURE AT SERVICE BRAKE PEDAL VALVE PRIMARY AIR SYSTEM DELIVERY

PORT?

DECISION

NO - Replace defective service brake pedal valve (Volume 3, WP

0429), M936 (Volume 3, WP

0430). Go to

Step (30) to verify problem is solved.

YES - Repair or replace blocked air line to double check valve #1 (Volume 5, WP

0805). Go to Step (30) to

verify problem is solved.

TM 9-2320-272-23-1

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