5
OPERATION & LEAKAGE CHECKS
GENERAL
A change in vehicle braking characteristics or a low pres-
sure warning may indicate a malfunction in one or the other
brake circuit, and although the vehicle air brake system
may continue to function, the vehicle should not be oper-
ated until the necessary repairs have been made and both
braking circuits, including the pneumatic and mechanical
devices are operating normally. If the brake valve does
not function as described above or leakage is excessive,
it is recommended that it be replaced with a new or remanu-
factured unit available at Bendix outlets. Always check the
vehicle brake system for proper operation after performing
brake work and before returning the vehicle to service.
OPERATING CHECK
Check the delivery pressure of both No. 1 and No. 2 circuits
using test gauges known to be accurate.
Note: The treadle or pedal will not be in a “normal” released
position until the air brake system is pressurized. The pedal
or treadle will rise to its normal release position as the brake
system is pressurized from 0 psi.
Depress the treadle to several positions between the fully
released and fully applied positions and check the delivered
pressure on the test gauges to see that it varies equally and
proportionately with the movement of the brake pedal.
After a full application is released, the reading on the test
gauges should fall off to zero promptly. It should be noted
that the No. 1 circuit delivery pressure will be about 4 psi
greater than the No. 2 circuit delivery pressure with both
supply reservoirs at the same pressure. This in normal for
this valve.
LEAKAGE CHECK
Make and hold a pressure application of 20 psi.
Coat the exhaust port and body of the brake valve with a
soap solution.
Leakage permitted is a 1" bubble in 3 seconds in both the
applied and released positions.
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.
8.
Use only genuine Bendix
®
replacement parts,
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically for such applications and
systems.
9.
Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.
10. Prior to returning the vehicle to service, make cer-
tain all components and systems are restored to
their proper operating condition.
VEHICLE PREPARATION
1. Park the vehicle on a level surface and block the wheels
and/or hold the vehicle by means other than the air
brakes.
2. Drain the air pressure from all vehicle reservoirs.
VALVE REMOVAL
1. Identify and mark or label all air lines and their respec-
tive connections on the brake valve to facilitate ease of
installation. Disconnect all air lines.
2. Mark the relationship of the valve body to the mounting
plate then remove the valve from its mounting on the
vehicle.
