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®
Bendix® PP-DC™ Park Control Valve
EXHAUST
SUPPLY 12
SUPPLY 11
SD-03-3619
SUPPLY 11
DELIVERY
21
EXHAUST
COVER
BUTTON
FIGURE 1 - PP-DC™ P ARK CONTROL VAL VE
DESCRIPTION
The Bendix® PP-DC™ park control valve is a push-pull,
manually operable on/off valve. It is dash board-mounted
and provides in-cab control of truck or bus parking brakes.
The valve is pressure sensitive – it automatically moves from
the applied to the exhaust position if total system pressure
drops below 20 to 30 psi. Also, manually pulling the button
will apply the parking brakes.
The PP-DC™ valve body is made of non-metallic, noncorrosive material, and the cover is available in two mounting
variations (see Figure 1). The valve is designed to accept
1/4" P.T. fittings or push-to-connect fittings that use SAE
J844D non-metallic air brake tubing.
Ports:
Port Embossed I.D.
Primary Reservoir Supply Supply 11
Secondary Reservoir Supply Supply 12
Delivery Delivery 21
Exhaust Exhaust 3
Operating pressure: 150 psi max.
Operating temperature: -40° to 200°F
Basic valve weight: Approximately .8 lbs.
BUTTON
OPERATION
GENERAL
The PP-DC™ valve receives its supply of air from the primary
service reservoir or the secondary service reservoir, whichever
is at the higher pressure. When the button is pushed in, the
valve delivers air to the spring brake chambers (usually
through a spring brake valve such as the Bendix® SR-1
valve and a relay or quick release valve). The air releases
the spring brakes for normal vehicle operation.
T o apply the parking brakes, the button is pulled out, which
exhausts the PP-DC™ valve delivery and releases air from
the spring brake chambers.
If total system pressure drops below 20 to 30 psi, the valve
will automatically “pop out,” which removes the hold-off air
in the chambers and applies the spring brakes.
P ARKING BRAKES RELEASED
T o release the parking brakes, the push-pull button is pushed
in. The PP-DC™ valve plunger moves, closing the exhaust
port with the exhaust seal and allowing the plunger o-ring to
move past the guide spool. Supply air then travels out the
delivery port to release the brakes.
Note that Figure 3 shows the primary service reservoir
supplying the PP-DC™ valve. The double check valve
diaphragm has sealed the secondary reservoir supply port
and allows air to pass from the primary reservoir into the
PP-DC™ valve.
™
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™
PP-DC
VALVE
SUPPLY (PRIMARY
RESERVOIR)
SUPPLY (SECONDARY
RESERVOIR)
DEL.
SR-1™ SPRING
BRAKE VALVE
EXH.
ANTI-CMPD.
LINE
FIGURE 2 - TYPICAL 4 X 2 TRUCK SCHEMATIC WITH PP-DC™ PARK CONTROL V ALVE
If primary service reservoir pressure drops below secondary
service reservoir pressure, the double check valve reacts as
shown in Figure 4. It seals the primary service reservoir
supply port and supplies the PP-DC™ valve with air from the
secondary service reservoir. As is shown, the push-pull button
remains in and the spring brakes remain released.
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
P ARKING BRAKES APPLIED
Figure 5 shows the PP-DC™ valve in the parking-brakesapplied position. This will occur if the driver manually pulls
out the push-pull button or if total system pressure drops to
below 20 to 30 psi.
When the button “pops out,” the exhaust seal moves to
open the exhaust port to atmosphere, allowing delivery line
pressure to exhaust. The plunger o-ring moves to seal off
supply pressure. Spring brake hold-off air is exhausted
through the spring brake relay valve.
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
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
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.
SERVICE
RELAY VALVE
QR-1C
VALVE
™
®
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SECONDARY
SERVICE RESERVOIR
SUPPLY
BUTTON
PLUNGER O-RING
PLUNGER
GUIDE SPOOL
DELIVERY
EXHAUST
SEAL
PRIMARY SERVICE
RESERVOIR
EXHAUST
FIGURE 3 - SPRING BRAKES RELEASED (PRIMARY RESERVOIR SUPPL Y)
PLUNGER O-RING
SECONDARY
SERVICE RESERVOIR
BUTTON
PLUNGER
GUIDE SPOOL
DELIVERY
SUPPLY
PRIMARY SERVICE
RESERVOIR
FIGURE 4 - SPRING BRAKES RELEASED (SECONDARY RESERVOIR SUPPLY)
EXHAUST
SEAL
EXHAUST
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SECONDARY
SERVICE RESERVOIR
SUPPLY
PLUNGER O-RING
BUTTON
PLUNGER
GUIDE SPOOL
DELIVERY
EXHAUST
SEAL
PRIMARY SERVICE
RESERVOIR
FIGURE 5 - P ARKING BRAKES APPLIED
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
certain all components and systems are restored
to their proper operating condition.
1 1 . For vehicles with Antilock Traction Control (A TC),
the ATC function must be disabled (A TC 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.
PREVENTIVE MAINTENANCE
Important: Review the Bendix Warranty Policy before
performing any intrusive maintenance procedures. A warranty
may be voided if intrusive maintenance is performed during
the warranty period.
No two vehicles operate under identical conditions, as a
result, maintenance intervals may vary. Experience is a
valuable guide in determining the best maintenance interval
for air brake system components. At a minimum, the
PP-DC™ valve should be inspected every 6 months or 1500
operating hours, whichever comes first, for proper operation.
Should the PP-DC™ valve not meet the elements of the
operational tests noted in this document, further investigation
and service of the valve may be required.
EXHAUST
SERVICE CHECKS
1. Remove any accumulated contaminants. Visually
inspect the valve’s exterior for excessive wear or physical
damage. Repair/replace as necessary .
2. Inspect all air lines connected to the valve for signs of
wear or physical damage. Repair/replace as necessary .
3. T est air line fittings for excessive leakage. Repair/replace
as necessary .
LEAKAGE AND OPERATIONAL TESTS
To perform the following tests, connect two separate 120
psi air sources to the PP-DC™ valve supply ports. Tee an
accurate test gauge into the supply lines, and provide for a
means to control supply line pressure. Connect a small
volume with a gauge to the delivery port.
LEAKAGE TEST
1. Supply the valve with 120 psi from the primary reservoir
supply port. With the button out, coat the exhaust port
and the plunger stem with a soap solution. Leakage
should not exceed a 1" bubble in 5 seconds. There
should be no leakage from the secondary reservoir supply
port.
2. With the button out, supply the valve with 120 psi from
the secondary reservoir supply port. There should be no
leakage from the primary reservoir supply port.
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SCREW
BUTTON
COVER
GUIDE
SPOOL
1
2
PLUNGER
STEM
PLUNGER
CHECK VALVE SEAT
7
BODY
3
8
9
INDEX TABS
4
5
6
FIGURE 6 - EXPLODED VIEW
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3. With the button in, coat the exhaust port and the plunger
stem with a soap solution. Leakage at both areas should
not exceed a 1" bubble in 3 seconds.
OPERA TIONAL TEST
1. With the button out, supply either supply port with 120
psi of air. Then push the button in. Air pressure should
rise in the delivery volume equivalent to supply pressure.
2. Pull the button out. Delivery pressure should exhaust to
0 psi.
3. Build each supply source to 120 psi. Decrease supply
pressure at the secondary service reservoir supply port
at a rate of 10 psi per second. Primary supply pressure
and delivery pressure should not drop below 100 psi.
Repeat the test for decreasing primary service reservoir
pressure.
4. Build each supply source to 120 psi. Then decrease
both supply pressures to below 20 to 30 psi. The button
should automatically “pop” out when pressure drops
within that range.
If the PP-DC
™
valve fails to function as described, or if
leakage is excessive, repair the valve or replace it at the
nearest authorized Bendix Commercial Vehicle Systems
parts outlet.
REMOVAL
1. Identify and mark or label all air lines and their
connections on the valve.
2. Remove the PP-DC™ valve from the vehicle and save the
mounting hardware.
INST ALLATION
1. Install the PP-DC™ valve in its location on the dashboard.
Using the mounting hardware saved in “REMOVAL,”
secure the valve to the vehicle.
2. Reconnect all air lines to the valve using the identification
made in “REMOV AL.”
3. Perform “OPERATIONAL AND LEAKAGE TESTS” before
placing the vehicle back in service.
DISASSEMBL Y
The following disassembly and assembly procedures are
for reference only . Always have the appropriate maintenance
kit on hand and use its instructions in lieu of those presented
here. Refer to Figure 6 throughout the procedure.
1. Turn the button counterclockwise to remove it from the
plunger stem.
2. Remove the four screws that secure the cover to the
body, and remove the cover.
3. Pull the plunger stem to remove the plunger and the
guide spool from the body .
4. Remove plunger spring(6) and discard.
5. If necessary, use a screwdriver to carefully remove the
check valve seat from the body . Be sure not to damage
the check valve seat or the body .
6. Remove and discard check valve seat o-rings(7) and (8).
7. Turn the body upside down and gently tap it on a flat
surface to remove check valve(9). Discard the check
valve.
8. Remove the guide spool from the plunger . Remove and
discard o-ring(1) from the guide spool.
9. Remove and discard o-rings(2), (3) and (5) from the
plunger. Also remove and discard exhaust seal(4).
CLEANING & INSPECTION
1. Wash all metal parts in mineral spirits and thoroughly
dry.
2. Inspect all re-usable parts for excessive wear or damage.
Inspect the body for gouges or deep scuffing. Replace
key numbers 1-9 (and any parts not determined usable)
with genuine Bendix replacements.
ASSEMBL Y
Before assembly , lubricate all o-rings, o-ring grooves, rubbing
surfaces and bores with Bendix silicone lubricant (Pc. No.
291 126) or equivalent.
1. Place check valve(9) into its seat in the body with its flat
surface facing upward. If necessary , reach into the body
to make sure the valve is seated evenly in the bore.
2. Install o-rings(7) and (8) on the check valve seat and
install the check valve seat into the body . Make sure the
seat is fully seated-its surface should be even with the
body’s surface.
3. Install plunger spring(6) into the body . Make sure it stands
upright and is seated properly in the body bore. (It should
surround the protrusion or “lip” at the bottom of the body
bore.)
4. Install o-rings(2), (3), (5) and exhaust seal(4) onto the
plunger. Then inst all the plunger into the body. Line up
the plunger’s index tabs with the spaces in the body
bore for ease of installation.
5. Install o-ring(1) onto the guide spool. Then install the
guide spool over the plunger and into the body . Press
the guide spool into place firmly .
6. Place the cover onto the body and secure with its four
screws. Torque to 35 in. lbs.
7. Thread the button clockwise onto the plunger stem. It
should take approximately 3 full button revolutions to
install it on the plunger . The protrusions on the side of
the plunger should line up with the button grooves. Push
on the button a number of times to make sure the plunger
moves freely throughout its range of motion.
NOTE: BEFORE PLACING THE VEHICLE BACK INTO
SERVICE, PERFORM THE “LEAKAGE AND
OPERA TIONAL TESTS” IN THIS MANUAL.
BW1739 © 2007 Bendix Commercial Vehicle Systems LLC. All rights reserved. 6/2007 Printed in U.S.A.
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