BENDIX AH-1B AIR HYD INTENSIFIER User manual

1
®
Bendix®AH-1B™Air Hydraulic Intensifier
SD-11-1326
DESCRIPTION
The AH-1B™air hydraulic intensifier is a hydraulic brake,
power booster which utilizes compressed air for its power
assist. Its function is to convert air pressure to hydraulic
pressure for use in the brake system.
TheAH-1B™intensifier consists of three major component
groups; a specially designed type 30 air actuator is bolted
to a single piston master cylinder which incorporates an
integralbrakefluidreservoir.Abracketinstalledbetweenthe
actuatorandmastercylinderprovidesameansformounting.
A float actuated, low fluid level, on/off electrical switch is
incorporated in the reservoir filler cap assembly. A two
“prong” connector is provided to permit the installation of a
vehicle electrical cable assembly. Switch actuation occurs
when the reservoir fluid level drops below the “minimum”
levelmarkingonthe reservoir.
RESERVOIR
DIAPHRAGM
PUSH ROD
AIRINLET
PRESSURE
PLATE
CLAMPRING
NON-PRESS
PLATE RETURN
SPRING
BOOT
ELECTRICAL
CONNECTOR
FILLERCAP
ASSY.
INDICATOR
SWITCH
FLOAT
COMPENSATING
VALVE
HYD.
DELIVERY
PORT
RETURN
SPRING
PISTON
ACTUATOR
LIP
PISTON
SEAL
MOUNTING
BRACKET
O-RING
DRAINHOLE
FIGURE 1
RESERVOIR
CAP
ELECTRICAL FLUID
LEVELINDICATOR
CONNECTION BRAKEFLUID
RESERVOIR
AIR
INLET
PORT
ACTUATOR
MOUNTING
BRACKET
MASTER
CYLINDER
BRAKEFLUID
DELIVERYPORT

2
DIAPHRAGM
APPLIED
POSITION
FIGURE3 -CUTAWAYVIEWOFAPPLIEDPOSITION
HYDRAULICFLUID
BEINGDELIVERED
COMPENSATING
TILTVALVESEALED
PISTONAPPLIED
POSITION
RETURN
SPRING
COMPRESSED
AIRAPPLIED
POSITION
SPRINGBRAKE
ACTUATOR
FIGURE2 - TYPICALAH-1B™AIR HYDRAULICINTENSIFIER SYSTEM
BRAKE
VALVE
PUSH-PULLVALVE
RELAY
VALVE
RESERVOIR
AH-1B™AIR OVER
HYDRAULIC
INTENSIFIER
HYDRAULIC
DISCBRAKE
COMPRESSOR
AIRDRYER

3
FIGURE4 - CUTAWAY VIEW OF RELEASEDPOSITION
AIRINLET
NON-APPLIEDPOSITION
OPERATION
BrakesApplied
Duringa brakeapplication,modulated airpressure from the
foot operated air brake valve enters the actuator inlet port.
Airpressure actingupon theareaof theactuatordiaphragm
causes the diaphragm and push rod assembly to move
toward the master cylinder. The actuator push rod forces
the master cylinder piston to move within its bore. Initial
forward travel of the piston moves the actuating lip of the
piston away from the stem of the compensating (tilt) valve
allowingit to close due to spring force. (Refer to Figure 2&
3.) Closure of the compensating valve shuts off the fluid
passagebetweenthecylinderboreandfluidreservoirwhich
allows hydraulic pressure to build and the brakes to apply.
Theamount of hydraulic pressure generated is dependent
uponthe air pressure applied to the air actuator.
Brakes Released
Whenair pressure is exhausted from the actuatorthepush
rod returns to the released position due to spring force.
With the push rod load removed, fluid pressure combined
with return spring force causes the piston to return to the
brakes released position. The actuator lip of the piston
contacts the stem of the compensating valve and unseats
the valve as the piston returns. When the compensating
valve opens, the passage between the fluid reservoir and
master cylinder bore is also open. Any excess fluid
remaining at the end of the stroke due to “pumping” and/or
volumechangeduetotemperature fluctuationis transmitted
backtothefluid reservoiras thecompensatingvalveopens.
Thepush rod is usedasthepiston stop in thefullyreleased
position. (Refer to Figure 4).
Fluid Level Indicator
Thereservoir fluidlevel isreducedas thebrakelinings wear
duetoanincreaseoffluidvolume required in the hydraulic
brakesystem.The float contained in the reservoir filter cap
assembly is suspended in the reservoir fluid and responds
to changes in the fluid level. As long as the reservoir fluid
level is adequate, a metal contact plate on top of the float
stem is held away from two electrical contacts. When the
reservoir fluid level drops below the “MINIMUM” fluid level
mark on the reservoir, the contact plate on the float stem
will move and complete the electrical circuit through the
switch.
DIAPHRAGM
NON-APPLIEDPOSITION
COMPENSATING TILT
VALVEUNSEALED
POSITION
HYDRAULIC
FLUID PORT
RETURN SPRING
NON-APPLIEDPOSITION
PISTON
NON-APPLIED
POSITION

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TECHNICAL SPECIFICATIONS
AH-1B™Air Hydraulic Intensifier Assembly
Power ratio - 20.2 to 1
Weight-approximately 2-1/2 pounds
Air Actuator
Effectiveareaofdiaphragmat2-1/8inchesofpushrodstroke
- approximately 28 sq.in.
Volume at 2-1/8 inches of push rod stroke - approximately
75 cubic inches.
Master Cylinder
Bore diameter - 1.38 inches
Maximum piston stroke - 2-1/8 inches
Maximum fluid displacement - 3.17 cubic inches
Fluid Reservoir
Volume - 33.5 cubic inch to “MAXIMUM” level mark with
capremoved.
PREVENTIVE MAINTENANCE
Every month, after 8,000 miles, or 300 operating hours;
1. Remove accumulated dirt and grime from the area
around the reservoir cover. With the ignition switch in
theon position, removethecover and hold inanupright
position and allow brake fluid in the tube of the cap to
drain back into the reservoir. Check to see if the low
fluid indicator bulb is operating (in cab of vehicle).
2. If thefluidlevel is low,fill to proper levelindicatedon the
side of the reservoir. CAUTION: Fill the reservoir with
type and grade of fluid recommended by the vehicle
manufacturer.
3. Check tightnessofthemountingnuts, air and hydraulic
fittings.
4. Make a visual inspection of air and hydraulic lines for
kinking, bending or fraying. Replace as necessary.
Every12months;100,000miles;or3,600operatinghours;
1. Perform the operating and leakage tests. Replace or
repair components or assemblies as indicated using
only genuine Bendix parts.
OPERATING AND LEAKAGE TESTS
1. Withvehicleairsystempressurebuilttogovernorcut-out,
makeandholdafullbrakeapplication.Holdforatleast
5 minutes. Using a soap solution, check for air leaks at
fittingsandairlines.Tightenand/orreplaceasnecessary.
Apply a soap solution around the actuator clamp ring.
Noleakageispermitted.Tightenorreplaceasnecessary.
Applya soapsolution totheactuator non-pressureplate
drainholes.Replace the actuator diaphragm if leakage
is detected.
2. Whileholdingthebrakevalve inthefully appliedposition,
check for hydraulic fluid leaks at all fitting connections
and at the hydraulic cylinders in the foundation brake.
Checkfor fluidleakageat the drainholesof theactuator
non-pressure plate. Repair or replace components as
necessary.
3. With the reservoir filter cap removed apply and fully
releasethebrakesseveraltimeswhileobservingthe fluid
inthe reservoir.CAUTION:WEARSAFETYGLASSES
ASFLUID MAYEXITTHERESERVOIR.
Aslightfluidturbulenceshould benoted atthebeginning
of the application and should immediately cease. If
prolongedturbulence isnoted,the mastercylindermust
berepaired orreplaced.
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURYOR DEATH:
When working on or around brake systems and
components, the following precautions should be
observed at all times:
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
When working around or under the vehicle, stop
the engine and remove the key from the ignition.
Always keep hands away from chambers as they
mayapply as system pressure drops. Always wear
safetyglasses.
2. 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
shouldbe used toprevent 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 the use of those tools.
4. Following the vehicle manufacturer’s
recommendedprocedures, deactivatethe electrical
system in a manner that safely removes all
electrical power from the vehicle.
5. If the vehicle is equipped with an air over hydraulic
brake system or any auxiliary pressurized air
system, 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.
6. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
component or pipe plug unless you are certain all
system pressure has been depleted.
7. Never exceed manufacturer’s recommended
pressure.

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FIGURE 5 - EXPLODED VIEW
FIGURE 6
8. Never attempt to disassemble a component until
you have read and understand all recommended
procedures. Some components contain powerful
springs and injury can result if not properly
disassembled. Use only proper tools and observe
all precautions pertaining to use of those tools.
9. Use only genuine Bendix®replacement parts,
components and kits.
A. Use only components, devices and mounting
and attaching hardware specifically designed
for use in hydraulic brake systems.
B. All replacement hardware, tubing, hose,
fittings, etc. must be of equivalent size, type
and strength as the original equipment.
10. 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.
11. Prior to returning the vehicle to service, make
certainallcomponentsandsystemsarerestoredto
their proper operating condition.
NON-PRESS
PLATE RETURN
SPRING
SPRING
SEAT BOOT
BUSHING
ASSEMBLY
DIAPHRAGM
PRESSURE
PLATE
NUT (2)
CLAMPRING
RESERVOIRCAP
ASSEMBLY
MASTER
CYLINDERBODY
LOCKWASHER
(2) PHILLIPS
SCREW(2)
SEAL
1-1/4”RES.
RETAINING
NUT
RESERVOIR
COMPENSATING
(TILT)VALVE
ASSEMBLY
RESERVOIR
MTG. PAD
SPRING
PISTONASSY.
(W/SEAL)
O-RING
MOUNTING
BRACKET
GASKET
WASHER(2)
ACTUATOR
NUT (2)
O-RING

6
FIGURE 7
FIGURE 8
FIGURE 9
REMOVAL FROM VEHICLE
1. Disconnect the hydraulic line from the delivery port of
themaster cylinderand plugtheline.Allow thehydraulic
fluid from the master cylinder to drain into a suitable
container.Remove reservoircover tofacilitatedrainage.
2. Disconnect the air line from the air actuator and cover
the end of the air line.
3. Remove the electrical connection from the low level
indicatoron thereservoircover.
4. Removethehardwarethatsecuresthe mountingbracket
of theAH-1B™intensifier to the vehicle and remove the
completeunit.
INSTALLING ON VEHICLE
1. InstallthehardwarewhichsecurestheAH-1B™intensifier
mountingbrackettothe vehicle.Torqueallhardwareper
thevehicle manufacturer’srecommendations.
2. Reconnecttheairlinetotheactuator.Useasmallamount
ofthread sealant.
3. Reconnect the hydraulic line to the master cylinder.
4. Connecttheelectricalterminalfromthelowfluidindicator
ontotheterminalonthe cap of the reservoir.
5. Fillthe mastercylinderfluid reservoir usingthetype and
gradefluid specified bythevehicle manufacturer.
6. Bleed the hydraulic brakes following the vehicle
manufacturer’srecommendedprocedure.
7. Refill the master cylinder fluid reservoir to replace fluid
lostduring the bleeding procedure.
DISASSEMBLY
General
The following procedure is presented for reference only.
Disassembly of the AH-1B™intensifier should not be
attemptedwithout having the appropriatemaintenancekits
or replacement parts on hand as some parts may be
damagedduring disassembly.
1. Drainthe hydraulic fluidfromthe reservoir.
2. Remove the two Phillips screws and lockwashers from
the bottom of the reservoir located at the reservoir
mountingpadon the master cylinder next to theflange.
3. Remove the reservoir cap and retain. DO NOT
DISASSEMBLECAP.Usinga1-1/4" socketremovethe
retaining nut on the inside of the reservoir. Reservoir is
nowfree of themastercylinder.Removethe seal onthe
bottomof the reservoir and discard. (RefertoFigure6.)
4. Remove the compensating valve assembly from the
master cylinder by placing a crescent wrench across
theflatsand turning counterclockwise. If only changing
the reservoir, do not remove the compensating valve
assembly as it cannot be replaced unless the master
cylinderisdisassembled.The compensatingvalve must
be replaced as an assembly (Figure 7).

7
FIGURE 10
5. Noteand marktheorientationoftheactuatorand master
cylinder to the mounting bracket. Remove the two nuts
and washers from the mounting studs of the actuator
(use a 15/16" socket wrench). Separate the master
cylinder and actuator from the mounting bracket and
retain the actuator for later disassembly. CAUTION:
Piston under spring load and retained by the push rod
only when compensating tilt valve assembly has been
removed.(Refer toFigure 8.)
6. Removethe o-ringfrom theflange ofthe mastercylinder
andthegasketbetweenthebracketandactuator.
7. Removethe piston assembly andspringfromthebody
of the master cylinder. (Refer to Figure 9.)
ActuatorDisassembly
8. Mark the relationship of the clamp ring, pressure and
non-pressureplates.Removethetwonutsandboltsfrom
theclampringoftheactuator(usea1/2" socketwrench).
Grasptheears of the clamping ring and spread slightly
until ring will come off and pressure plate and
non-pressure plates separate. CAUTION: Parts are
spring loaded. Use a press or clamp to retain the push
rodandreturn spring during disassembly.
9. Removethe springseat, spring, andbootfrom the push
rod and separate the diaphragm from the push rod.
(NOTE: Do not separate the diaphragm from the push
rod.)If the diaphragm is to be replaced,anewpush rod
and diaphragm assembly will be required.
CLEANING & INSPECTION
1. Wash all master cylinder parts retained during
disassemblyin cleanDOT3 or 4brakefluid. CAUTION:
DO NOT use any solvent other than clean brake fluid
for cleaning or flushing master cylinder parts. The use
of unapproved solvents with a trace of mineral oil will
damagerubberparts.
2. Remove allsediment orforeign materialfrom thebottom
of the fluid reservoir. If the reservoir is equipped with
filters, make certain they are thoroughly cleaned. If the
filtersare thoroughlyplugged and/orcannotbe cleaned,
the entire brake system should be flushed. If the filter
cannotbecleaned, it may be removed after the system
is flushed.
3. Inspect the condition of the piston. Measure the major
diameter(aroundthe top edge of the o-ring groove and
pistonactuatorlip)ofeachpistoninseveralplacesaround
its circumference. The difference between the largest
and smallest measurement on each of the diameters
measured should not exceed .005 inches (.13mm). If
thediameterofthepistonvariesmorethanthemaximum,
themastercylindershouldbereplacedorrepairedusing
a maintenance kit.
4. Examinethemastercylinderboreaftercleaning.Ifpitting,
scratchingorvisiblewear patternsare noted,the master
cylindershouldbereplaced.Dirt, gumand stainedareas
notremovedduringcleaningcanbepolishedwithcrocus
cloth.DONOTUSEEMERYCLOTHORSANDPAPER.
Master cylinder bores may be honed provided that the
diameterisnotincreasedsubstantially.Honingtoremove
scratches and pitting will most likely increase the bore
diameter beyond the sealing ability of piston seals. To
makecertaintheborediameterhasnotbeenexcessively
increased, measure the piston clearance in the master
cylinder bore. Using a feeler gauge make certain the
clearancedoes notexceed.010 inches (.25mm). Make
certainthatnoburrsorsharpedgesremaininthecylinder
bore.Thoroughly clean and rinse the mastercylinderin
brakefluid after polishing orhoning.
5. Inspectthe actuationpushrodreturnspring forcorrosion
andpitting and replace if necessary.
6. Inspect the actuator diaphragm for wear and abrading.
(It is recommended that the diaphragm be replaced
whenever a complete disassembly of the AH-1B™
intensifiertakesplace.)
7. The push rod boot should be replaced each time a
completedisassembly is undertaken.
ASSEMBLY
ActuatorAssembly
1. Install the boot onto the push rod assembly. The small
I.D. of the boot must be forced over the larger O.D. on
the shaft of the push rod. Place the spring over the
push rod and boot and place the spring seat onto the
spring. Force large flange end of the boot through the
center hole of the spring seat.

8
FIGURE 11
2. Place the push rod and diaphragm assembly into the
pressure plate and place non-pressure plate onto the
push rod. Check to assure that the spring is in proper
position(each endcontainedand centered inthespring
guides).
3. Orientthe pressureandnon-pressure plates asmarked
and compress the spring by pushing down on the
non-pressureplate.Retain witha clamporlightpressure
from a press. Be sure the ferrule on the pressure plate
is properly oriented and the edges of the non-pressure
plate, diaphragm, and pressure plate are equally
distributedaround the entire circumference.
4. Install clamping ring and retain with the two bolts and
nuts.Torque to 130-150 inch pounds. IMPORTANT: Be
surethebeadsofthepressureplateandthenon-pressure
plateare containedby the clamping ringafull360°. Tap
around the circumference of the clamp ring to assure it
isseatedevenly all around.
5. Install a new gasket on the mounting studs of the
nonpressure plate of the assembled actuator and put
theassembly aside.
Master Cylinder Assembly
6. Installnewo-ringsonthemastercylindermountingflange
and the master cylinder piston.
7. Carefully insert the spring and piston into the master
cylinder body. Making certain not to damage the seal
and o-ring. The lip seal and o-ring must enter the body
last. Depress and hold the piston by inserting a dull
object into the recess in the end of the piston. Piston
actuatorlipshouldbecompletelypastthe compensating
TRTvalveassembly port to allow for proper installation
of the compensating valve assembly. Install the
compensatingvalveassembly into the threaded port of
the top of the master cylinder. Be sure compensating
valve is installed between the two larger diameters on
the piston. Torque to 30-40 foot pounds. NOTE: The
compensating valve assembly should retain the piston
assembly in the master cylinder if installed correctly.
(See Figure 10.)
8. Install a new seal on the bottom of the reservoir and
place both on the master cylinder. Be sure reservoir is
oriented so that holes for the Phillips screws line up
with the holes on the master cylinder. Install the two
Phillips screws and lockwashers and tighten snugly.
9. Installthe reservoirretainingnut ontothecompensating
valvethrough the reservoir coveropening.Use a 1-1/4"
socket and torque to 13-16 foot pounds.
10. Installthe reservoirfiller capassembly onthereservoir.
11. Clamp the mounting bracketsecurelyinavise,making
sure it is oriented so that the unit may be assembled,
and lining up the marks made prior to disassembly.
12. Install thenewgasket(6) overthe mountingstudsofthe
brakechamber. Makesurethegasket is flat againstthe
top of the brake chamber.
13. Placethebrakechamber ontothe mountingbracketwith
thepushrod extending through the center hole and the
mountingboltsextending through the outer holes.
14. Install the master cylinder/reservoir assembly onto the
brake chamber mounting studs and retain with nuts(4)
andwashers(5).Torque to100-115foot pounds.NOTE:
The end of the push rod must enter the recess of the
master cylinder piston.
Bench Bleeding
Before installing the AH-1B™intensifier assembly on the
vehicle the master cylinder should be bench bled. Follow
the vehicle manufacturer’s recommendations in lieu of the
following.
1. Plug outlet port and secure cylinder in a vise with front
end tilted slightly downward. NOTE: Bleeder tubes or
Bendixbleedingkit #74013 may also be used following
the kit instructions enclosed. (Refer to Figure 11.)
2. Fill reservoir with brake fluid. Refer to vehicle
manufacturer’s manual for fluid requirements.
3. Apply and release air pressure to the actuator several
times.
4. Re-position themastercylinder in the visewiththefront
end tilted slightly up. Again, apply and release air
pressureseveral times.NOTE: Whenusingthis method
ofbenchbleeding,themastercylinderwillnotbecapable
of being stroked once all the air is removed.
5. InstalltheAH-1B™intensifier onthevehicle andperform
the “Operating and Leakage Tests” prior to placing the
vehiclein service.
BW1599 © 2004 Bendix Commercial Vehicle Systems LLC All rights reserved. 4/2004 Printed in U.S.A.