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1

®

SD-03-3410

DESCRIPTION

The VM-3

 

is a control manifold serving as a manifold unit

for air passages between cab and engine compartment and
housing a double check valve and PR-4

 pressure protection

valve.

OPERATION

1. The double check valve receives supply air from the rear

(primary) supply system, through port No. 3 on Fig. 1,
and front (secondary) supply system, through port No.
1 on Fig. 1, and delivers whichever is higher in pressure
to the spring brake system and through another port to
the trailer supply through the dash mounted PP-7

 tractor

protection control valve.

2. The PR-4

 pressure protection valve receives supply air

from the front (secondary) supply port and supplies
protected air to three ports, one on the engine side and
two on the cab side. The PR-4

 valve will deliver air to

these ports only after the front supply system has built
up to at least 60 psi.

3. Supply air for the trailer control hand valve is taken from

a port inside the cab supplied from the rear (primary) air
supply.

The location and function of the various ports are shown in
Fig. 1 for the engine side of the VM-3

 manifold and in Fig.

2 for the cab side. The chart shown on Fig. 1 explains the
purpose and function of each port on the engine side and
the chart shown on Fig. 2 the cab side.

WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO  AVOID
PERSONAL INJURY OR DEATH:

When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the

parking brakes, and always block the wheels.
Always wear safety glasses.

2. Stop the engine and remove ignition key when

working under or around the vehicle.  When
working in the engine compartment, the engine
should be shut off and the ignition key should be

removed. Where circumstances require that the
engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.

3. Do not attempt to install, remove, disassemble or

assemble a component until you have read and
thoroughly understand the recommended
procedures.  Use only the proper tools and observe
all precautions pertaining to use of those tools.

4. If the work is being performed on the vehicle’s air

brake system, or any auxiliary pressurized air
systems, make certain to drain the air pressure from
all reservoirs before beginning ANY work on the
vehicle.  If the vehicle is equipped with an AD-IS

air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir.

5. Following the vehicle manufacturer’s

recommended procedures, deactivate the electrical
system in a manner that safely removes all
electrical power from the vehicle.

6. Never exceed manufacturer’s recommended

pressures.

7. Never connect or disconnect a hose or line

containing pressure; it may whip. Never remove a
component or plug unless you are certain all
system pressure has been depleted.

Bendix

®

 VM-3

 Firewall Manifold

FIGURE 1 - 

ENGINE SIDE

NO.1

NO.4

NO.2

NO.3

NO.9

NO.8

NO.7

NO.6

NO.5

Summary of Contents for VM-3 FIREWALL MANIFOLD

Page 1: ...utions should be observed at all times 1 Park the vehicle on a level surface apply the parking brakes and always block the wheels Always wear safety glasses 2 Stop the engine and remove ignition key when working under or around the vehicle When working in the engine compartment the engine should be shut off and the ignition key should be removed Where circumstances require that the engine be in op...

Page 2: ...2 in cab Suggested use supplies secondary reservoir air to the balance port of the SR 1 spring brake control valve Port Ident on No Casting Function 1 Frt Gauge Connects to gauge for No 2 circuit Blue reservoir 2 Prk Sup Supplies air from double check valve Red to park control valve 3 Rear Gauge Connects to gauge for No 1 circuit Green reservoir 4 Hand Brake Supplies air from No 2 circuit reservoi...

Page 3: ...estigation and service of the valve may be required SERVICE CHECKS OPERATINGAND LEAKAGE CHECKS 1 Start engine and charge both sides of dual system 2 Stopengine drainthefrontbrakereservoiranddisconnect tube fitting at port No 1 in Fig 1 identified as Frt Sup Blue Excessive leakage would indicate a faulty double check valve 3 Restore and recharge both systems Drain the rear brake reservoir and disco...

Page 4: ...ove the PR 4 valve piston assembly Do not attempt to remove the retaining ring and stem from the piston ASSEMBLY Before assembly lubricate all o rings bores and mating surfaces with BW 650M lubricant pc no 291126 Dow Corning 55M Replace any worn or deteriorated o rings and shuttle item 2 in Fig 5 if necessary Install shuttle in guide in body and install cap nut After cleaning and lubricating assem...

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