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 1016 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

c.

Disconnect delivery line from left rear-rear rear spring and service brake chamber adapter

fitting (Volume 3, WP

0435). Refer to point to point schematics.

d.

Disconnect pressure gauge and tee from vehicle and return air line to original condition.

e.

Move tee to between disconnected service brake chamber and delivery line.

f.

Verify pressure gauge is connected to tee.

g.

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

NOTE

Air pressure to service brake chambers must compare with reading on primary air

pressure gauge. Air pressure to spring and service brake chambers must compare with

reading on secondary air pressure gauge.

h.

Assistant fully applies and holds service brakes while comparing pressure gauge reading to instrument

panel secondary air pressure gauge reading.

i.

Pressure gauge should read 90 to 130 psi.

j.

Both readings should be similar.

CONDITION/INDICATION

IS THERE PROPER AIR PRESSURE AT THE LEFT REAR-REAR REAR SPRING AND SERVICE BRAKE

CHAMBER?

DECISION

NO - Go to Step (27).

YES - Go to Step (29).

TM 9-2320-272-23-1

0120

0120-27