BENDIX M-40QR Mounting instructions

1
Supply Port
(Casting has
“1, SUP”)
Exhaust Port
(Body has
“3, EXH”)
Supply Port
(Casting has
“1, SUP”)
Exhaust Port
(Body has
“3, EXH”)
Electrical
Connector
Mounting Holes
(.33" Diameter
Through Body)
Alternate Push-to-
Connect Version,
Showing Optional
Packard Connector
Electrical
Connector
Delivery Port
(Casting has
“2, DEL”)
Bendix® M-40HF™
Modulator
(Height = 4.75”)
Bendix®M-40QR™
Modulator
(Height = 3.75”)
SD-13-4958
DESCRIPTION
The Bendix®M-40QR™(quick release) and M-40HF™(high
ow) pressure modulator valves (PMVs) are high-capacity,
on/off air valves that incorporate a pair of electrical
solenoids for control. See Figure 1. The solenoids provide
the electro-pneumatic interface between the vehicle’s
electronic control system and the air brake system. For
example, the PMV is used to control the braking function
of service actuators during antilock activity.
Bendix®M-40QR™& M-40HF™Pressure Modulator Valves
Figure 1 - M-40QR™& M-40HF™Pressure Modulator Valves
Bendix®M-32™
Modulator
Figure 2 - Previous Bendix®M-32™Modulators
OE and Service New Bendix®M-40QR™
and M-40HF™ modulator valves
manufactured after February 2014,
contain two parallel ribs on each side of
the Supply and Delivery ports as shown
here. These ribs identify these modulators
as a genuine Bendix®product. If the OE
or Service New valve was manufactured
after this date and does not contain these
ribs, it is not a genuine Bendix®product.
Bendix®M-32QR™
Modulator

2
The modulator consists of a die cast metal and plastic body
that houses one normally-open solenoid, one normally-
closed solenoid, and an inlet and exhaust diaphragm
valve. A three-pin weather-resistant electrical connector
is an integral part of the modulator solenoid assembly
and delivers the vehicle controller’s commands to the
modulator. Two mounting holes are provided for frame or
crossmember mounting of the valve.
The Bendix®M-40QR™modulator is the direct replacement
for the Bendix®M-32QR™modulator (See Figure 2). The
Bendix M-40QR modulator has a bias valve to provide an
internal quick-release function.
The supply, delivery, and exhaust ports on the Bendix M-40
modulators have embossed identication codes.
Port ID Air Hose
Connection Function
1, SUP Supply Air enters from a valve (typically
foot, relay, or quick release).
2, DEL Delivery Air is delivered to the service
actuators.
3, EXH Exhaust Air is vented to the atmosphere.
Figure 3 - Port Designation and Function
APPLICATIONS
Bendix M-40™modulators may be used for various purposes
on a vehicle, including ABS and stability interventions. In
applications using these PMVs, an external quick release
valve may also be required, depending on the system
design. Where the modulator is used for individual wheel
control applications, it is typically the last control valve
through which air passes on its way to the service brake
actuator. See Figure 4 for a typical system schematic.
PRESSURE MODULATOR VALVE (PMV) AND
TRACTION CONTROL VALVE (TCV) CHUFF TEST
A wiring harness connects the vehicle modulators to the
controller. The ABS controller is able to simultaneously,
and independently, control the individual modulators.
Bendix®Electronic Control Units (ECUs) perform a Bendix-
patented PMV and TCV Chuff Test. The Chuff Test is
an electrical and pneumatic PMV test that can assist
maintenance personnel in verifying proper PMV wiring and
installation. This test is performed only when the vehicle
is stationary (if the vehicle moves, the Chuff Test will not
be performed).
NOTE: If there are any active Diagnostic Trouble Codes
(DTCs), the stop lamp cross-check portion of the Chuff Test
will not be carried out until all DTCs are fully diagnosed and
corresponding repairs are successfully conducted. The
ESP/ATC dash indicator lamp ATC/ESP Lamp –a lamp that
indicates when stability functions, including traction control,
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,
fittings, wiring, etc. must be of equivalent size, type and
strength as original equipment and be designed specifically
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 specifically 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.

3
C
S
roll stability program, or yaw control are operating– will also
be illuminated when there are active ABS, ATC, or ESP
DTCs. (See the Glossary on page 8 for more information
on these terms.)
See Figure 5. When ignition power is applied, each
modulator solenoid is briey energized. If the air system
is fully charged –and the service brake pedal is depressed
during ignition – the modulator creates a single, sharp
audible “chuff” of air pressure. Bendix ECUs will perform
a PMV Chuff Test on all installed modulators in the order
shown in Figure 5. The pattern will then repeat itself.
Service &
Spring Brake
Chamber
Antilock
Controller
Slack Adjuster
Wheel Speed
Sensor
Wheel Speed
Sensor
Wheel Speed
Sensor
Yaw Rate
Sensor
Steering
Angle Sensor
Service
Brake
Chamber
Brake
Valve
Glad Hands
Spring
Brake
Chamber
Service Brake
Chamber
SL-4™Stop Light Switch
TP-5™Tractor
Protection Valve
TCS -9000™
Trailer
Control
Valve
Pressure
Modulator
Valve
Pressure
Modulator
Valve Pressure Modulator Valve
Pressure
Modulator
Valve
Pressure Modulator Valve
Antilock Relay Valve
Antilock
Traction
Relay
Valve
Air Disc
Brake
For Illustration Purposes Only, Both
Air Disc Brakes And Foundation
Drum Brakes Are Shown At Either
Side Of The Axles.
Air Disc
Brakes
Foundation
Drum Brakes
Foundation Drum
Brakes
Trailer
(Supply)
Trailer
(Control)
Secondary
Brake
Circuit
Secondary
Brake Circuit
Primary
Brake
Circuit
Primary
Brake Circuit
Figure 4 - Typical System Diagram (4S-4M System Shown)
1. Steer Axle Right PMV
2. Steer Axle Left PMV
3. Drive Axle Right PMV
4. Drive Axle Left PMV
5. Additional Axle Right PMV
6. Additional Axle Left PMV
7. Trailer PMV
Driver
Right Steer
Left Steer
Right
Additional
Left
Additional
Right Drive
Left Drive
7
1
2
3
4
5
6
Figure 5 - Typical Vehicle Orientation and Chuff
Sequence

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ANTILOCK OPERATION
GENERAL
See Figure 6.
The rst four rows of this table show normal vehicle braking
where the PMV does not intervene. In the case of a
rapid, non-antilock release of the brakes (e.g. if the driver
releases the brakes after a severe brake application), the
Bendix®M-40QR™ PMV assists the quick release of the
brakes by being the point at which the air is exhausted.
The nal four rows of the table show the actions taken
during an antilock braking event.
If equipped with a Bendix®EC-60™(or later) advanced
controller, following the completion of the second round
of PMV & TCV Chuff Tests, the controller (if congured to
do so) will perform a test to cross-check the trailer PMV
operation with the vehicle stop lamps. If the trailer
PMV circuit is mis-wired (including the steer axle TCV),
the PMV will exhaust a large amount of air, or none at all.
OPERATION
Mode Modulator
Type
Hold
Solenoid
State
Exhaust
Solenoid
State
Description
Normal Braking
Normal,
Non-Antilock,
Brake Application
HF and QR De-energized De-energized
Air pressure supplied to the modulator exits
the modulator delivery port and ows to the
service brake chambers.
Non-Antilock
Hold HF and QR De-energized De-energized
When the desired air pressure is attained in
the service brake chambers, the air pressure
in the system levels off.
Normal,
Non-Antilock,
Relatively “slow”
Brake Release
HF and QR De-energized De-energized
Air from the brake chambers moves back
through the modulator in the reverse
direction as it owed during application.
Simultaneously, a small amount of air will
generally be expelled from the modulator
exhaust port.
Rapid,
Non-Antilock,
Exhaust
(e.g., the driver
releases the
brakes after a
severe brake
application)
QR De-energized De-energized
The internal bias piston blocks air from the
brake chamber from moving back through the
modulator. Instead, all the air is exhausted
out the modulator exhaust port.
HF De-energized De-energized
Air from the brake chambers moves back
through the modulator in the reverse
direction as it owed during application.
Simultaneously, air will be expelled from the
modulator exhaust port.
Antilock Braking
Antilock Apply HF and QR De-energized De-energized
Air pressure supplied to the modulator exits
the modulator delivery port and ows to the
service brake chambers.
Antilock Exhaust HF and QR Energized Energized Air from the brake chambers exhausts
through the modulator exhaust port.
Antilock Hold HF and QR Energized De-energized
The modulator prevents supply air from
passing through the modulator and, at the
same time, prevents air from the brake
chambers from exhausting.
Antilock
"Reapply" HF and QR De-energized De-energized
The modulator re-applies air to the brakes in
the same manner it did during a non-antilock
event.
Figure 6 - Bendix®M-40QR™& M-40HF™Modulators: Operational Modes

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ANTILOCK APPLY MODE
If a service brake application is made and the antilock
system detects an impending wheel lockup, the antilock
controller will make a controlled brake application using
the modulator.
In order to control the brake application, the coils of the two
solenoid valves contained in the modulator are energized,
or de-energized, in a pre-programmed sequence by the
antilock controller. When a solenoid coil is energized,
and – depending on whether the exhaust or hold solenoid
is energized – it either opens or closes, thereby causing
the exhaust or reapplication of air pressure to the brake
actuator. The solenoids in the modulator are controlled
independently by the Electronic Control Unit (ECU).
ANTILOCK EXHAUST MODE
When wheel lock is detected or imminent, the antilock
controller energizes the supply and exhaust solenoids in
the modulator.
Further delivery of air to the brake chamber is prevented,
and air is allowed to exhaust through the exhaust port.
ANTILOCK HOLD MODE
The antilock controller will place the modulator in the hold
position when information from the wheel speed sensors
shows that the correct wheel speed (braking force) has
been attained. The antilock controller will also place
the modulator in the hold position – prior to entering the
reapply mode – when it detects recovery from a locked
wheel condition.
In this mode of operation, the exhaust passage is sealed,
holding the air pressure in the brake chamber at that level.
At the same time, no application air is permitted to ow to
the brake chamber.
The modulator can enter both the antilock exhaust or
reapply mode from the antilock hold mode depending on
the needs of the antilock controller.
ANTILOCK “REAPPLY” MODE
If the antilock controller senses that wheel speed has
increased sufciently enough to allow re-application of
braking pressure, without further wheel lock-up, it permits
the supply air to re-apply air to the brakes in the same
manner it did during a non-antilock event.
PREVENTIVE MAINTENANCE
GENERAL
Read and follow the General Safety Guidelines on
page 2 of this document.
Perform the tests and inspections presented at the
prescribed intervals. If the modulator fails to function as
described, or if the leakage is excessive, replace it with a
new Bendix® brand unit, available at any authorized parts
outlet.
EVERY MONTH, 10,000 MILES, OR
350 OPERATING HOURS
1. Remove any accumulated contaminates and visually
inspect the exterior for excessive corrosion and physical
damage.
2. Inspect all air hoses and wire harnesses connected to
the modulator for signs of wear or physical damage.
Replace as necessary.
3. Test air line ttings for leakage and tighten or replace
as necessary.
4. Perform the routine OPERATION & LEAKAGE TESTS
described below.
OPERATION & LEAKAGE TESTS
OPERATION TEST
This test uses the Chuff Test (described on page 3).
To properly test the function of the modulator will require
two (2) service technicians.
1. Park the vehicle on a level surface and block or chock
the wheels. Release the parking brakes and build the
air system to governor cut-out.
2. Turn the engine ignition key to the OFF position then
make and hold a full brake application.
3. With the brake application held and one (1) service
technician posted at one (1) of the modulators, turn
the vehicle ignition key to the ON position. One or
two short bursts of air pressure should be noted at the
modulator exhaust. Repeat the test for each modulator
on the vehicle. If at least a single burst of exhaust is
not noted or the exhaust of air is prolonged and not
short, sharp, and well dened, perform the Electrical
Tests.

6
LEAKAGE TEST
1. Park the vehicle on a level surface and block or chock
the wheels. Release the parking brakes and build the
air system to full pressure.
2. Turn the engine OFF and make 4 or 5 brake applications
and note that the service brakes apply and release
promptly.
3. Build system pressure to governor cut-out and turn the
engine OFF.
Twist-Lock
Connector
(Bayonet
Connector)
Optional Adapter
Figure 7 - Exterior Views and Electrical Connections
12
3
1
23
12
3
1
23
12
3
1
23
12
3
1
23
12
3
1
23
43
41
2
42
3
1
Packard
Terminal
Name
Function
41 Source
42 Hold
43 Exhaust
Bayonet
Terminal
Name
Function
1 Exhaust
2 Source
3 Hold
Bendix® M-40HF™
Modulator
Bendix®M-40QR™
Modulator
Twist-Lock Connector
(Bayonet Connector)
Packard Electric
Connector
(280 Series)
4. After determining the pressure loss with the brakes
released (2 psi/minute allowed), make and hold a
full service brake application. Allow the pressure to
stabilize for one minute.
5. Begin timing pressure loss for two minutes while
watching the dash gauges for a pressure drop. The
leakage rate for the service reservoirs should not ex-
ceed four (4) psi within two minutes for a single vehicle,
six (6) psi within two minutes for a tractor/trailer, and
eight (8) psi within two minutes for a tractor with two
trailers.
6. If either circuit exceeds the leakage values above, apply
a soap solution to the exhaust port of the modulators
and any other components in the respective circuit,
then apply the service brakes.
7. The leakage at the exhaust port of most Bendix
components, including the M-40™modulators, should not
exceed a one-inch bubble in three seconds. If leakage
at the modulator is determined to exceed the maximum
limits, replace the modulator.
ELECTRICAL TESTS
1. Before testing the solenoid assembly of a suspect
modulator, its location on the vehicle should be
conrmed using the troubleshooting procedure for the
specic antilock controller in use. (See the Service Data
Sheet available on the document library on bendix.com.)
2. Proceed to the modulator in question and inspect its
wiring connector. Disconnect the connector and test the
resistance between the pins on the modulator. Refer
to Figure 7.
A. HOLD to SOURCE (41-42):
12V systems: Read 4.8 to 5.6 Ohms.
24V systems: Read 13.9 to 16.3 Ohms.
B. EXHAUST to SOURCE (41-43):
12V systems: Read 4.8 to 5.6 Ohms.
24V systems: Read 13.9 to 16.3 Ohms.
C. Individually test the resistance of each pin to
vehicle ground and note there is NO continuity.
If the resistance readings are as shown, the wire
harness leading to the modulator may require repair or
replacement. Before attempting repair or replacement
of the wire harness, refer to the test procedures
specied for the antilock controller in use for possible
further testing that may be required to substantiate the
wire harness problem. If the resistance values are not
as stated, replace the modulator.

7
Figure 9 - Bendix M-40QR & M-40HF Modulators DIN Symbol
MODULATOR REMOVAL
1. Locate the modulator that will be replaced and clean
the exterior.
2. Identify and mark or label all air hoses and their
respective connections on the valve to facilitate ease
of installation.
3. Disconnect both air lines and the electrical connector.
4. Remove the modulator from the vehicle.
5. Remove any air hose ttings present. These ttings
will be re-used in the replacement modulator.
MODULATOR INSTALLATION
1. Install all previously-removed air hose ttings, making
certain thread-sealing material does not enter the
valve.
2. Install the assembled valve on the vehicle.
3. Reconnect both air lines to the valve using the
identication marks made during step 5 of Modulator
Removal.
4. Reconnect the electrical harness to the modulator.
5. After installing the valve, test all air ttings for excessive
leakage and tighten as needed.
TECHNICAL INFORMATION
Mode Modulator Type
Port
Options
Supply Port (from brake, relay, or
quick release valve): 1/2" NPT
Delivery Port (brake actuator):
• 1/2" NPT
• Push-to-connect for 1/2" tubing
Solenoid
Voltage
12 Volts DC Nominal, optional 24 Volt
available
Weight 1.35 pounds
Maximum
Operating
Pressure
150 psi gauge
Operating
Temperature
Range
-40°F (40°C) to 185°F.
[A short-term operating temperature
of 230°F (110°C) for up to 10% of the
valve’s lifetime is acceptable.]
Pressure
Differential 1 psi maximum (supply to delivery)
Mounting
Hole Sizes 0.33" diameter through body
Figure 8 - Bendix®M-40QR™& M-40HF™Modulators
Packard
Terminal
Name
Bayonet
Terminal
Name
Function
41 2 Source
42 3 Hold
43 1 Exhaust
Valve
Port Function
1 Supply
2 Delivery
3 Exhaust
Bendix®
M-40HF™
Modulator
Bendix®
M-40QR™
Modulator

8
SD-13-4958 Rev. 001 © 2018 Bendix Commercial Vehicle Systems LLC, a member of the Knorr-Bremse Group • 10/18 • All Rights Reserved
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GLOSSARY
See the Service Data Sheet for the vehicle’s Electronic
Control Unit for more information.
ABS - Antilock Brake System.
ABS Event - Impending wheel lock situation that causes the
ABS controller to activate the modulator valve(s).
ABS Indicator Lamp - An amber lamp which indicates the
operating status of an antilock system. When the indicator lamp
is on, ABS is disabled and the vehicle reverts to normal brake
operation.
ATC - Automatic Traction Control. An additional ABS function
in which engine torque is controlled and brakes are applied
differentially to enhance vehicle traction.
ATC / ESP Lamp - A lamp that indicates when stability functions,
including traction control, roll stability program, or yaw control
are operating.
ECU - Electronic Control Unit.
ESC / ESP®- Electronic Stability Program. Full stability system,
offering both roll and yaw stability to help provide loss of control
and rollover mitigation.
Diagnostic Trouble Code (DTC) - A condition that interferes with
the generation or transmission of response or control signals in
the vehicle's ABS system that could lead to the functionality of
the ABS system becoming inoperable in whole or in part.
J1939 - A high speed data link used for communications between
the ABS ECU engine, transmission, and retarders.
PMV - Pressure Modulator Valve. An air valve which is used to
vent or block air to the brake chambers to limit or reduce brake
torque.
QR - Quick Release. Quick release valves allow faster release
of air from the brake chamber after a brake application.
RSP - Roll Stability Program. An all-axle ABS solution that helps
reduce vehicle speed by applying all vehicle brakes as needed,
reducing the tendency to roll over.
SAS - Steering Angle Sensor.
TCV - Traction Control Valve.
YC - Yaw Control. Helps stabilize rotational dynamics of vehicle.
YRS - Yaw Rate Sensor.