BENDIX AH-4 AIR HYD INTENSIFIER User manual

1
®
Bendix®AH-4™Air Hydraulic Intensifier
SD-11-1357
DESCRIPTION
TheAH-4™isanair-over-hydraulicintensifier available with
pressure ratios of 13.5 to 1, 17 to 1 and 23.5 to 1. The air
chamber is a rotochamber, either type 30, 36 or 50. The
mastercylinder design is identical inall units;however, the
master cylinder is available with seals for hydraulic brake
fluid,orformineraloil.Themastercylinderdisplaces6cubic
inches with the type 36 or type 50 actuator and 4.6 cubic
inches with the type 30.
The type 30 unit is designed for dusty operation, as in off-
highway, with the non-pressure cavity protected by a tight
fittingheadand a filterforbreathing non-pressure air.
The master cylinder may have a remote or direct mounted
reservoir.Fig.1showsa23.5to1unitwithintegral reservoir.
OPERATION
TheAH-4™intensifieris normally used to provide hydraulic
pressure to hydraulic disc brakes on an air braked vehicle.
It may be used in any application where it is desired to
“intensify” available air pressure to a higher hydraulic
pressure.100 psi airpressure introduced tothe center port
at the rear of the rotochamber will produce approximately
1,350psihydraulic pressure atthemaster cylinder delivery
port with a type 30 rotochamber, 1,700 psi with a type 36
rotochamber, and approximately 2,350 psi with a type 50
rotochamber.
PREVENTIVE MAINTENANCE
Important: Review the warranty policy before performing
anyintrusivemaintenanceprocedures.Anextendedwarranty
maybevoidedif intrusive maintenance isperformedduring
thisperiod.
Becausenotwovehiclesoperateunderidenticalconditions,
maintenanceintervalswillvary.Experienceisavaluableguide
indeterminingthe best maintenanceinterval for avehicle.
Every Month, After 8,000 Miles, or 300 Operating Hours
1. Remove the cover and gasket from the brake fluid
reservoir, takingextreme care to firstremoveall dirt and
foreignmaterial so that no foreign material is permitted
to get into the hydraulic fluid. If the fluid lever is low,
properfluidshouldbeadded.CAUTION-Thecoverand
gasket will each indicate whether hydraulic brake fluid
or mineral oil should be added. The gasket for brake
fluid is black and the gasket for mineral oil is green.
2. Checkthestroke warning switch bygraspingthe switch
extension rod underneath the rubber boot and pulling
firmly. With the ignition turned on, the warning light in
the cab should light. NOTE: If the warning light comes
on during a service application, the vehicle should be
broughtinfor service immediately.
3. Check tightness of mounting nuts, air and hydraulic
fittings.
Every12Months,100,000Miles, or3,600OperatingHours
1. Disassemble and clean all parts.
2. Install new rotochamber diaphragm, reservoir gasket,
sealsor anyparts worn or damaged.
OPERATINGAND LEAKAGE TESTS
Operating Test
1. Withtheairsystembuiltuptogovernorcut-outpressure,
makeand hold a full brake application. Holdfor atleast
5 minutes. Check the rear of the rotochamber and the
rotochamberhead vents forair leakage by coating with
a soap solution.
2. While still holding the brake application, check for
hydraulic fluid leaks at all fitting connections and at the
disc brake calipers.

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OUTER DIAPHRAGM
CLAMP
FIGURE 1
DIAPHRAGM
GUIDE
STROKEWARNINGSWITCH
FILTER
1
76
8
4
2
3
5
3. Observethe stroke warning light. Ifthe mastercylinder
piston seal leaks, the master cylinder, under sustained
pressure,willslowlystrokeuntilthestrokewarningswitch
isactivated.
REMOVAL FROM VEHICLE
1. Disconnect the hydraulic line from the delivery port of
themastercylinder and allow thehydraulicfluid to drain
into a suitable receptacle. The drainage may be
expeditedbyremovingthe reservoir cover andgasket.
2. Disconnect the air line from the rotochamber, the fluid
supply line from the master cylinder (in the case of
remote mounted reservoirs), and the electrical
connectionsfromthe stroke warningswitch mounted in
theheadof the rotochamber.
3. Removethenutsfromthestudswhich holdthemounting
brackets and remove the AH-4™intensifier from the
vehicle.
INSTALLING ON VEHICLE
1. RemounttheAH-4™intensifier,reconnecttheairdelivery
line to the rotochamber and the electrical connections
to the stroke warning switch.
2. Inthecaseofremotemounted reservoir, reconnect the
reservoirto the mastercylinder.
3. Beforeaddinghydraulicfluid,cycletheAH-4™intensifier
very carefully by making a very light brake application.
Therotochambershouldextendtofullstrokeandoperate
the stroke warning switch, causing the warning light to
come on in the cab. This will test the stroke warning
system. Release the application and reset the stroke
warningswitch.
4. Remove plugs, reconnect the fluid lines and bleed the
master cylinder. The master cylinder itself may be bled
bygravitybyfillingthereservoirandopeningthebleeder
fittingoppositethedischargeport.Whenclearfluidflows
from the bleeder fitting, it may be closed. If the rest of
the system needs bleeding, it may be done by opening
the appropriate bleed fitting and cycling the AH-4™
intensifier. Hydraulic brake fluid equivalent to DOT 3
specifications should always be used. Some AH-4™
intensifier units are designed to be used with mineral
oil, in which case, the reservoir cover will clearly so
designate.Rubberpartsforusewithmineraloilarecolor
coded.Reservoirgasket diaphragm is green,sealsand
o-ringsarebrown.
TERMINALPERSAE
18582- PLACES PUSH TO RESET
2.45
PUSHPLATE
PUSH ROD
INNER
DIAPHRAGM
CLAMP
DIAPHRAGM

3
FIGURE 2
3.19MAX
.60
.74
3.12 REF
STROKE
8
9
11
10
DISASSEMBLY
RotochamberfromMasterCylinder FIGURE 1
1. Remove four cap screws (1), and remove the master
cylinder from the rotochamber.
Rotochamber
1. Remove theGapscrews(2)whichholdtherotochamber
headinthe shell and removethehead (6), return spring
(7), and spring guide (8).
2. Remove the nuts (3) from the body which secure the
outer clamp (4) to the body. On some units, one of the
mounting brackets is also retained by three of these
nuts.
3. Place body, openend downon bench and tap the ends
ofthestuds(5)withabrassdrift,leadorplastichammer.
The studs should be tapped on one side of the air inlet
and then the other alternately, to free the outer clamp.
4. Grasp the push rod and, by pulling and wiggling the
entire assembly consisting of push rod and plate,
diaphragm guide, diaphragm, inner and outer clamps
should ease out of the body.
5. Removetheouterclamp.
6. Remove nuts from inside of diaphragm guide.
7. Disassemble the inner diaphragm clamp, diaphragm,
push plate rod assembly, and diaphragm guide.
8. Removethestrokewarningswitchfromthe rotochamber
headandbenchtestforelectricalintegrity.IfOK,replace
inhead.
DISASSEMBLY
Master Cylinder FIGURE 2
1. Clean exterior of master cylinder and drain any
remainingfluid,Inthecaseofremotemountedreservoir,
drain and clean the reservoir.
2. Secure master cylinder in a vise. Depress piston (1)
Fig. 2, at least 1/2 in. and hold. This may be done with
a simple tool as shown in Figs. 3 and 4. Remove the
four self-threading bolts (9) securing the adapter block
or the reservoir to the master cylinder. Remove the
adapter block or reservoir and the compensating valve
(3) and spring (11).
CAUTION The compensating valve must be removed
before any attempt is made to remove the hydraulic
piston assembly (see Fig. 5).
3. Removeretainingring(8) and stopwasher(7).
4. Remove piston holding tool and remove piston (1) and
spring (4).
5. Removecapnut(10)fromadapterblock.Removeo-ring
(2) from cap nut and compensating valve seal (5) from
adapter block or reservoir.
7
6
5
43
2
1

4
FIGURE 3
FIGURE 4
FIGURE 5
ASSEMBLY
Rotochamber
1. Position the diaphragm on end in the inner diaphragm
clamp (Fig. 1). The smaller diameter end of the
diaphragmshould be against the diaphragmclamp.
2. Place and install the diaphragm guide within the
diaphragm and over the inner diaphragm clamp studs.
3. Install the push plate push rod assembly within the
diaphragm guide and over the inner diaphragm clamp
studs.
4. Install nuts on the inner diaphragm clamp studs and
tighten securely (55-70 inch pounds)
5. Place the assembly consisting of the push rod, push
plate, diaphragm guide, diaphragm, and inner clamp
inside of the outer clamp.
6. Roll the free end of the diaphragm back and over the
end of the outer diaphragm clamp.
7. Lubricate the inside wall of the body and the rolled
surface of the diaphragm with BW652M Type 2.
8. Slide the above assembly into the body.The endof the
diaphragmshould fitsnugly against the shoulder in the
body.Positiontheouterdiaphragmclampstudsthrough
theholes at the end of the body, installnutsandtighten
securely. Torque to 100-125 inch pounds.
9. Installspring guide, and install springover push rod.
10.Install cover over push rod and into body.Attach cover
to body with cap screws, tightening securely. Torque to
110-150 inch pounds.
ASSEMBLY
Master Cylinder
1. Washthe cap nut,adapter block, and cylinder castings
with alcohol or mineral spirits and dry thoroughly.
2. Carefullyclean the filterscreen. (6)
ContinuedonPage 5.
3/8 X 18 BOLT
3-1/8
4-5/8
6
4-5/8
C.R.S.

5
FIGURE 7
FIGURE 6
FIGURE 8
FIGURE 9
3. Installthe new o-ring(2) on the cap nutafter lubricating
with the fluid to be used in the master cylinder or Dow
Corning55-M pneumatic grease.Thread the cap nut in
the adapter block and torque to 300 inch pounds.
4. Coat the new compensating seal (5) with fluid or Dow
Corning 55-M pneumatic grease and install in mating
grooves in bottom of adapter block or reservoir.
5. Coat bore inmastercylinder with fluidto be used,place
spring (4) in piston assembly (1 ) and slide both into
bore of master cylinder (fig. 6).
6. Placethestopwasher (7) and retainingring(8) over the
center post of the retaining tool, depress the piston (1)
(see Fig. 7). Make certain the retaining ring is properly
seatedinitscorrespondinggrooveinthemaster cylinder
casting (see Fig. 8). CAUTION - Keep retaining tool
in place until step 8 is completed!!
7. Withpiston still depressed,install compensating spring
(11) and compensatingvalve (3). Set adapter block(or
reservoir) in place. The master cylinder casting should
preferably be held in a horizontal position for this
operation.Start the fourself-threadingbolts (9) by hand
to prevent cross threading and torque to 150- 200 inch
pounds.Careshouldbetaken that the compensating
valve is properly located before the adapter block
or reservoir is located and snugged down (Fig. 9).
The piston may now be released by removing the
retainingtool.
8. A simple check may be made to determine that the
compensating valve is properly installed. Apply air
pressure on the discharge port of the master cylinder.
With the piston released, air should back flow through
the compensating valve and out the adapter fitting or
reservoir. Depress thepistonatleast1/4in.Airpressure
shouldnow be trappedin the mastercylinder and there
should be no evidence of back flow out the adapter
block or reservoir.
CAUTION-50psiairpressurewillcreateapproximately
100 pounds of additional reactive force on the piston.
The piston retaining tool should, therefore, be used for
thistest.
9. Installthe master cylinderon the rotochamberwith four
3/8 in. cap screws torqued to 300 inch pounds.

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WARNING! PLEASE READAND 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
enginebeinoperation,EXTREMECAUTIONshould
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. Useonlytheproper 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,makecertaintodrain the air pressurefrom
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
recommendedprocedures,deactivatetheelectrical
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
certainallcomponentsandsystemsarerestoredto
their proper operating condition.
BW1455 © 2004 Bendix Commercial Vehicle Systems LLC. All rights reserved. 4/2004 Printed in U.S.A.