BENDIX R-12DC User manual

1
Figure 1 – Bendix®R-12DC®Relay Valve Exploded View
*Crack Pressure is the amount of control
pressure required by the valve to initiate
air delivery. For Crack pressures other
than 4 psi, a differential spring is used
in the assembly to produce the required
valve response.
(Models designed to have a 4 psi crack
pressure do not require a differential spring.)
Primary Control
Port 1/4 NPT
Secondary
Control Port
1/4 NPT
Cap Screw
Torx®
Screw
Differential Spring
(Controls Crack Pressure*)
(Not required for Most
Models. See Below.)
Vertical
Delivery
Ports
Supply Port
Horizontal Delivery
Ports
Differential Springs
BENDIX®R-12DC®RELAY VALVE MAJOR MAINTENANCE KIT
Kit Contents
Item No. Description Qty.
1 Valve Spring 1
2 Check Valve Guide 1
3 Check Valve 1
4 O-Ring 1
5 O-Ring 1
6 O-Ring 1
7 Inlet & Exhaust Valve 1
8 Valve Retainer 1
9 Spring 1
10 O-Ring 1
11 O-Ring 1
12 Exhaust Cover 1
13 Retaining Ring 1
14 Lubricant (Not Shown) 1 6
7
8
2
34
5
1
9
13
12
11
10
Valve
Cover
Double
Check
Cover
Relay Piston
Valve Body

REMOVAL AND INSTALLATION
REMOVAL
1. Block and hold the vehicle by means other than the air
brakes.
2. Drain the air brake system reservoirs.
3. If the entire Bendix®R-12DC®valve is to be removed,
identify the air lines to facilitate the installation. Prior
to disassembly, remove as much contamination as
possible from the exterior of the device taking care to
keep all contamination from entering the open ports.
4. Disconnect the air lines from the valve*.
5. Remove the valve from the reservoir or if remotely
mounted, remove the mounting bolts and then the
valve.
*It is generally not necessary to remove the entire valve
to service the inlet/exhaust valve. The inlet/exhaust valve
insert can be removed by removing the snap ring, exhaust
cover assembly, and then the inlet/exhaust valve.
Drain all reservoirs before attempting to remove the inlet
exhaust valve.
DISASSEMBLY
NOTE: Prior to disassembly, mark the location of the
mounting bracket to the cover and the cover to the body.
The valve body may be lightly clamped in a bench vise
during disassembly, however, over-clamping will result
in damage to the valve and result in leakage and/or
malfunction. If a vise is to be used, position the valve so
that the jaws bear on the supply ports on opposing sides
of the valve’s body. (See Figure 1).
1. Remove the four cap screws securing the mounting
bracket and cover to the body. Retain the cap screws
for reuse.
2. Discard the mounting bracket.
3. Remove and discard the sealing o-ring (5) from the
valve cover.
a. Remove the two Torx®screws securing the double
check cover to the valve cover.
b. Remove the double check cover from the valve
cover and remove and discard the valve spring
(1), check valve guide (2), check valve (3), and
o-ring (4).
4. Remove and discard the sealing o-ring (5) from the
cover, and mounting bracket.
2
GENERAL SAFETY GUIDELINES
WARNING! PLEASE READ AND
FOLLOW THESE INSTRUCTIONS
TO AVOID PERSONAL INJURY OR DEATH:
When working on or around a vehicle, the following
guidelines should be observed AT ALL TIMES:
▲Park the vehicle on a level surface, apply the parking
brakes and always block the wheels. Always wear personal
protection equipment.
▲Stop the engine and remove the 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.
▲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.
▲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 a Bendix®AD-IS®air dryer system, a Bendix®
DRM™dryer reservoir module, or a Bendix® AD-9si®air
dryer, be sure to drain the purge reservoir.
▲
Following the vehicle manufacturer’s recommended
procedures, deactivate the electrical system in a manner
that safely removes all electrical power from the vehicle
.
▲Never exceed manufacturer’s recommended pressures.
▲Never connect or disconnect a hose or line containing
pressure; it may whip and/or cause hazardous airborne
dust and dirt particles. Wear eye protection. Slowly open
connections with care, and verify that no pressure is
present. Never remove a component or plug unless you are
certain all system pressure has been depleted.
▲Use only genuine Bendix®brand replacement parts,
components and kits. Replacement hardware, tubing, hose,
fi ttings, wiring, etc. must be of equivalent size, type and
strength as original equipment and be designed specifi cally
for such applications and systems.
▲Components with stripped threads or damaged parts should
be replaced rather than repaired. Do not attempt repairs
requiring machining or welding unless specifi cally stated
and approved by the vehicle and component manufacturer.
▲Prior to returning the vehicle to service, make certain all
components and systems are restored to their proper
operating condition.
▲For vehicles with Automatic Traction Control (ATC), the ATC
function must be disabled (ATC indicator lamp should be
ON) prior to performing any vehicle maintenance where
one or more wheels on a drive axle are lifted off the ground
and moving.
▲The power MUST be temporarily disconnected from the
radar sensor whenever any tests USING A DYNAMOMETER
are conducted on a vehicle equipped with a Bendix®
Wingman®system.
▲You should consult the vehicle manufacturer's operating
and service manuals, and any related literature, in
conjunction with the Guidelines above.

5. Remove the relay piston from the valve body and retain
for reuse.
6. Remove and discard the o-ring (6) from the relay
piston.
7. Depress and hold the exhaust cover (12) and remove
and discard the retaining ring (13) from the valve body.
8. Slowly release the holding force on the exhaust cover
assembly (12) to relax the spring.
9. Remove and discard the following parts:
a. Exhaust cover assembly (12)
b. O-rings (10 & 11)
c. Spring (9)
d. Inlet & exhaust valve (7)
e. Valve retainer (8)
CLEANING AND INSPECTION
1. Wash all metal parts in mineral spirits and dry them
thoroughly.
(NOTE: When servicing the Bendix®R-12DC®valve,
all springs and all rubber parts should be replaced.)
2. Inspect all metal parts for deterioration and wear, as
evidenced by scratches, scoring, and corrosion.
3. Inspect the exhaust valve seat on the relay piston for
nicks and scratches which could cause excessive
leakage.
4. Inspect the inlet valve seat in the body for scratches
and nicks, which could cause excessive leakage.
5. Inspect the check valve seat in the R-12DC valve cover
and make sure all internal air passages in this area are
open, clean, and free of nicks and scratches.
6. Replace all parts not considered serviceable during
these inspections and all springs and rubber parts. Use
only genuine Bendix®replacement parts, available from
any authorized Bendix parts outlet.
ASSEMBLY
NOTE: All torques specied in this manual are assembly
torques and can be expected to fall off slightly after
assembly. Do not re-torque after initial assembly torque
fall. For assembly, hand wrenches are recommended.
Prior to assembly, lubricate all o-rings, o-ring bores and any
sliding surface with the lubricant (14) provided.
Wash all remaining parts in mineral spirits and dry
thoroughly. Lightly lubricate all o-rings, o-ring grooves,
body bores and sliding surfaces.
1. Install the o-rings (10 & 11) in the exhaust cover (12).
2. Install the o-ring (6) on the relay piston.
3. Install the sealing o-ring (5) on the valve cover.
4. Install the valve retainer (8) on the inlet and exhaust
valve (7) and insert both in the valve body.
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5. Install the spring (9) in the valve body.
6. Install the exhaust cover assembly (12) in the valve
body. Depress and hold the exhaust cover assembly
in the valve body.
7. Install the retaining ring (13) in the body. Make certain
the retaining ring is completely seated in the groove in
the body.
8. Install the relay piston in the valve body.
9. Install the o-ring (4) on the double check cover. Install
the spring (1), check valve guide (2) and check valve
(3) in the cover. Install the cover and torque the Torx®
head screws to 80–100 in-lbs.
10. Referring to the marks made during disassembly, install
the cover.
11. Install the mounting bracket (not shown) on the cover.
12. Install the four cap screws in the cover and torque to
80–100 in-lbs.
INSTALLATION
1. Clean the air lines.
2. Inspect all lines and/or hoses for damage and replace
as necessary.
3. Install the valve and tighten the mounting bolts.
4. Connect the air lines to the valve (plug any unused
ports).
5. Test the valve as outlined in Operational and Leakage
Test.
OPERATIONAL AND LEAKAGE TEST
1. Chock the wheels, fully charge the air brake system,
and adjust the brakes.
2. Make several brake applications and check for prompt
application and release at each wheel.
3. Check for inlet valve and o-ring leakage. Make this
check with the service brakes released. Coat the
exhaust port and the area around the retaining ring with
a soap solution; a one inch bubble in three seconds
leakage is permitted.
4. Check for exhaust valve leakage. Make this check with
the service brakes fully applied. Coat the outside of the
valve where the cover joins the body to check for seal
ring leakage; no leakage is permitted.
If the valves do not function as described above, or if
leakage is excessive, it is recommended that the valves
be replaced with new or remanufactured units or repaired
with genuine Bendix®parts, available at any authorized
Bendix parts outlet.

4S-1258 Rev. 004 © 2019 Bendix Commercial Vehicle Systems LLC, a member of the Knorr-Bremse Group • 03/19 • All Rights Reserved.
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