BENDIX TU-FLO 700 COMPRESSOR User manual

1
®
SD-01-335
Bendix®TU-FLO®700 Air Compressor
COMPRESSOR NAMEPLATE
SER
NO.
BW
NO.
MANUFACTURED BY
BENDIX
TU-FLO 700
Two methods are employed for cooling the Tu-Flo®700
compressor during operation. The cylinder head is
connected to the engine’scoolingsystem,whilethecylinder
hasexternalfinsforefficient aircooling.
AllTu-Flo®700compressorsutilize theengine’spressurized
oilsystem tolubricatetheinternalmovingparts.Anameplate
is attached to the crankcase to identify the compressor.
Thenameplatedisplaysa Bendix piece numberorinsome
cases an engine or vehicle manufacturer’s piece number,
alongwithaserialnumber.
DESCRIPTION
The function of the air compressor is to provide and main-
tain air under pressure to operate devices in the air brake
and/or auxiliary air systems
TheTu-Flo®700compressor isatwocylinder,singlestage,
reciprocatingcompressorwith arateddisplacementof 15.5
cubicfeetofairperminute at 1250 R.P.M.TheTu-Flo®700
compressor is constructed from three major assemblies,
the head, the cylinder block and the crankcase.
The head houses the discharge valving and is installed on
the upper portion of the cylinder block. The cylinder block
containsthecylinderbores andinletvalvesand is mounted
to the crankcase. The crankcase houses the crankshaft
andmainbearings.
Variousmountinganddrive configurations, required by the
numerous vehicle engine designs, are available. Two
governor mounting pads are located on either side of the
cylinderblockto provideconvenientgovernor mounting.
EXTERIOR BENDIX®TU-FLO®700AIR COMPRESSOR
(CROSSSECTION)
CRANKCASE
DISCHARGE
CAP NUT
PISTON
PISTON
RINGS
CRANKSHAFT
CONNECTING
ROD
DISCHARGE
VALVE
SPRING
INLET
VALVE
SPRING INLET
VALVE
DISCHARGE
VALVE
DISCHARGE
VALVE SEAT
UNLOADER
MECHANISM

2
OPERATION
The compressor is driven by the vehicle engine and is
operating continuously while the engine is running.Actual
compressionofairiscontrolledbythecompressorunloading
mechanism and the governor. The governor is generally
mountedonthecompressorandmaintainsthebrakesystem
air pressure to a preset maximum and minimum pressure
level.
INTAKE AND COMPRESSION OF AIR (LOADED)
During the down stroke of the piston, a slight vacuum is
createdbetweenthetonofthepistonandthehead,causing
theflatcircularinletvalve to move upandoffitsseat. (Note
the flat square discharge valve remains on its seat.)
Atmosphericairisdrawnthroughtheair strainerbytheopen
inlet valve and into the cylinder (see Fig. 2). As the piston
begins its upward stroke, the air that was drawn into the
cylinder on the down stroke is being compressed. Air
pressureontopof theinletvalveplusthe force ofitsspring,
returns the inlet valve to its seat. The piston continues the
upward stroke and compressed air then flows by the open
discharge valve, into the discharge line and on to the
reservoirs (see Fig. 3).As the piston reaches the top of its
stroke and starts down, the discharge valve spring and air
pressureinthe dischargelinereturns thedischargevalve to
itsseat.Thispreventsthecompressedairin the discharge
line from returning to the cylinder bore as the intake and
compression cycle is repeated.
NON-COMPRESSION OF AIR (UNLOADED)
Whenairpressureinthereservoirreachesthecut-outsetting
of the governor, the governor allows air to pass from the
reservoirintothecavitybeneath the unloader pistons. This
liftstheunloaderpistons and plungers. Theplungersmove
upandholdtheinletvalvesoff their seats (see Figure 4).
With the inlet valves held off their seats by the unloader
pistonsandplungers, airispumped backandforth between
the two cylinders. When air is used from the reservoir and
thepressuredropsto the cut-in setting of the governor, the
governor closes and exhausts the air from beneath the
unloader pistons. The unloader saddle spring forces the
saddle,pistonsandplungersdownandtheinletvalvesreturn
to their seats. Compression is then resumed.
COMPRESSOR & THE AIR BRAKE SYSTEM
GENERAL
The compressor is part of the total air brake system, more
specifically,thechargingportion of theairbrakesystem.As
acomponentintheoverall system its condition,dutycycle,
proper installation and operation will directly affect other
components in the system.
Powered by the vehicle engine, the air compressor builds
theair pressurefortheairbrakesystem.The aircompressor
istypicallycooledbythe engine coolant system, lubricated
by the engine oil supply and has its inlet connected to the
engine induction system.
As the atmospheric air is compressed, all the water vapor
originally in the air is carried along into the air system, as
well as a small amount of the lubricating oil as vapor. If an
air dryer is not used to remove these contaminants prior to
enteringtheairsystem,themajority,butnotall,willcondense
in the reservoirs. The quantity of contaminants that reach
the air system depends on several factors including
MACK
MACK
"FOXHEAD" CUMMINS
DETROIT
DIESEL
VARIOUS COMPRESSOR MOUNTINGS

3
installation,maintenanceandcontaminanthandlingdevices
inthesystem.Thesecontaminantsmusteitherbeeliminated
prior to entering the air system or after they enter.
DUTYCYCLE
The duty cycle is the ratio of time the compressor spends
buildingairtothetotalenginerunning time.Aircompressors
are designed to build air (run "loaded") up to 25% of the
time. Higher duty cycles cause conditions that affect air
brake charging system performance which may require
additional maintenance. Factors that add to the duty cycle
are: air suspension, additional air accessories, use of an
undersizedcompressor,frequentstops,excessive leakage
from fittings, connections, lines, chambers or valves, etc.
RefertoTableAintheTroubleshootingsectionfor aguideto
variousdutycyclesandtheconsiderationthat mustbegiven
tomaintenanceofothercomponents.
COMPRESSORINSTALLATION
While the original compressor installation is usually
completed by the vehicle manufacturer, conditions of
operation and maintenance may require additional
consideration.Thefollowing presents baseguidelines.
DISCHARGELINE
Thedischargelineallows theair, water-vaporandoil-vapor
mixture to cool between the compressor and air dryer or
reservoir.Thetypicalsize ofavehicle'sdischarge line, (see
column2 ofTableAintheTroubleshootingsection)assumes
a compressor with a normal (less than 25%) duty cycle,
operating in a temperate climate. See Bendix and/or other
airdryermanufacturer guidelines asneeded.
The discharge line must maintain a constant slope down
fromthecompressortotheair dryer inlet fitting orreservoir
toavoidlowpointswhereicemay formandblock theflow.If,
instead, ice blockages occur at the air dryer or reservoir
inlet,insulationmaybeaddedhere,oriftheinletfittingisa
typical 90 degree fitting, it may be changed to a straight or
45degreefitting.Shorterdischarge linelengthsorinsulation
may be required in cold climates.
While not all compressors and charging systems are
equippedwithadischarge line safetyvalvethiscomponent
isrecommended.Thedischargelinesafetyvalveisinstalled
in the cylinder head (Tu-Flo®550/750) or close to the
compressor discharge port and protects against over
pressurizingthecompressor intheevent ofadischargeline
freezeup.
FIGURE 1A - SYSTEM DRAWING
AirDryer
Reservoir Drain
Service Reservoir
(Supply Reservoir)
Compressor
Governor
(Governor plus Synchro valve
for the Bendix®DuraFlo™596
Compressor)
Discharge
Line Optional“Ping”Tank
OptionalBendix®PuraGuard®QC™
OilCoalescingFilter
The Air Brake Charging System supplies the
compressedairforthe brakingsystemaswellas otherair
accessories for the vehicle. The system usually consists
of an air compressor, governor, discharge line, air dryer,
andservice reservoir.
FIGURE 1B - DISCHARGE LINE SAFETY VALVE
HOLE
THREAD

4
DISCHARGELINETEMPERATURE
When the temperature of the compressed air that enters
the air dryer is within the normal range, the air dryer can
removemostofthechargingsystemoil.If the temperature
ofthecompressedairisabovethenormalrange,oilasoil-
vapor is able to pass through the air dryer and into the air
system. Larger diameter discharge lines and/or longer
dischargelinelengthscanhelp reduce the temperature.
Theairdryer contains afilterthatcollects oildroplets,anda
desiccantbed thatremoves almostalloftheremainingwater
vapor. The compressed air is then passed to the air brake
service (supply) reservoir. The oil droplets and the water
collected are automatically purged when the governor
reaches its "cut-out" setting.
For vehicles with accessories that are sensitive to small
amounts of oil, we recommend installation of a Bendix®
PuraGuard®QC™oilcoalescingfilter,designedtominimize
the amount of oil present.
LUBRICATION
Since all Tu-Flo®700 compressors are connected to the
engine’s pressurized oil system, a continuous flow of oil is
providedtothecompressor,whichiseventually returned to
the engine. Oil is fed into the compressor in various ways,
forexample:through therearend cover, thedriveend ofthe
crankshaftorthrough thefrontflangeadapter.Anoil passage
in the crankshaft conducts pressurized oil to the precision
sleeve main bearings and to the connecting rod bearings.
Splash lubricationofthecylinderbores,connectingrodwrist
pin bushings, and the ball type main bearings, on some
models,is obtainedasoilisforcedoutaroundthecrankshaft
journalsbyengineoilpressure.
Checktheexterior of thecompressorforthe presence ofoil
seepageandrefer totheTROUBLESHOOTINGsection for
appropriatetestsandcorrective action.
OIL PASSING
All reciprocating compressors currently manufactured will
pass a minimal amount of oil. Air dryers will remove the
majority of oil prior to entrance into the air brake system.
ForparticularlyoilsensitivesystemstheBendix®PuraGuard®
QC™oil coalescing filter can be used in conjunction with a
Bendixairdryer.
If compressor oil passing is suspected, refer to the
TROUBLESHOOTING section and TABLE A for the
symptoms and corrective action to be taken. In addition,
Bendix has developed the "Bendix Air System Inspection
Cup"orBASICtesttohelpsubstantiatesuspectedexcessive
oilpassing.The stepstobefollowed whenusingtheBASIC
test are presented in APPENDIX A at the end of the
TROUBLESHOOTINGsection.
FIGURE 2 - INTAKE
INTAKE
STRAINER
STROKE
TO RESERVOIR
INLET VALVE
UNLOADER
PLUNGER
TO GOVERNOR
INTAKE
STRAINER
STROKE
TO RESERVOIR
TO GOVERNOR
PISTON
DISCHARGE
VALVE UNLOADER
PLUNGER
STROKE
INLET VALVE
TO RESERVOIR
UNLOADER
PLUNGER
INTAKE
STRAINER
TO GOVERNOR
PISTON
DISCHARGE
VALVE
DISCHARGE
VALVE
INLET VALVE
FIGURE 3 - COMPRESSION
FIGURE 4 - UNLOADING
PISTON

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DRY ELEMENT—PLEATED PAPER AIR
STRAINER
Every 20,000 miles or 800 operating hours:
Removethespringclips from either sideofmountingbaffle
andremovethecover.Replacethepleatedpaperfilterand
remount the cleaned cover making sure the filter is in
position. Be sure to replace the air strainer gasket if the
entire air strainer is removed from the compressor intake.
(Note:Some compressorsarefittedwithcompressorintake
adapterswhich allowthe compressorintaketobeconnected
to the engine air cleaner.) In this case, the compressor
receives a supply of clean air from the engine air cleaner.
Whentheengineairfilter ischanged,thecompressorintake
adaptershouldbechecked.If it is loose,removetheintake
adapter, clean the strainer plate, if applicable, and replace
theintakeadapter gasket,andreinstalltheadaptersecurely.
Check line connections both at the compressor intake
adapterand attheengineaircleaner.Inspecttheconnecting
line for ruptures and replace it if necessary.
COOLING
Airflowingthrough theenginecompartmentfrom theaction
oftheengine’sfan andthemovementofthe vehicleassists
incoolingthecrankcase. Coolant flowingfromtheengine’s
cooling system through connecting lines enters the
compressorandflowsthroughthe internal passages inthe
cylinder block and head and back to the engine. Proper
coolingisimportantinmaintainingdischargeairtemperatures
belowthe400°Frecommended maximum.
PREVENTIVE MAINTENANCE
Regularly scheduled maintenance is the single most
importantfactorinmaintainingtheairbrakechargingsystem.
RefertoTableAintheTroubleshootingsectionfor aguideto
variousconsiderationsthatmustbegiventothemaintenance
of the compressor and other related charging system
components.
Important Note: Review the warranty policy before
performing any intrusive maintenance procedures. An
extendedwarrantymaybevoided if intrusive maintenance
isperformedduringthis period.
Everymonth,300operatinghoursoraftereach10,000miles,
dependingontheoperating conditions,experienceandthe
typeofstrainerused,servicetheairstrainer.
POLYURETHANE SPONGE STRAINER
Every 5000 miles or 150 operating hours:
Remove and wash all of the parts. The strainer element
should be cleaned or replaced. If the element is cleaned, it
should be washed in a commercial solvent or a detergent
andwatersolution.Theelementshouldbesaturatedinclean
engine oil, then squeezed dry before replacing it in the
strainer. Be sure to replace the air strainer gasket if the
entireairstrainerisremoved from the compressor intake.
FIGURE 5 - POLYURETHANE SPONGE STRAINER
FIGURE 6 - PAPER AIR STRAINER DRY ELEMENT-
PLEATED
FIGURE 7 - COMPRESSOR INTAKE ADAPTER

6
Every 6 months, 1800 operating hours or after each
50,000 miles:
Remove the discharge head fittings and inspect the
compressordischargeportanddischargelineforexcessive
carbondeposits.Ifexcessivebuildup is noted in either,the
discharge line must be cleaned or replaced and the
compressor checked more thoroughly, paying special
attention to the air induction system, oil supply and return
system, and proper cooling. If necessary, repair or replace
thecompressor.Checkforproper belt andpulleyalignment
andbelt tension.Adjustifnecessary,payingspecialattention
not to over tighten the belt tension. Check for noisy
compressor operation, which could indicate a worn drive
gear coupling or a loose pulley. Adjust and/or replace as
necessary. Check all compressor mounting bolts and
retightenevenlyif necessary.Checkfor leakageandproper
unloadermechanismoperation.Replace if defectiveinany
way.
Every 24 months, 7200 operating hours or after each
200,000 miles:
Perform a thorough inspection as indicated below and
dependinguponthe resultsofthis inspectionorexperience,
disassemble the compressor, clean and inspect all parts
thoroughly,repairorreplace allwornordamagedpartsusing
only genuine Bendix replacements or replace the
compressorwithagenuine Bendix remanufacturedunit.
Important:Shoulditbenecessarytodraintheenginecooling
systemtopreventdamage from freezing,thecylinderhead
of the compressor must also be drained.
GENERAL SERVICE CHECKS
INSPECTION
Itisoftheutmost importance that the compressorreceives
a clean supply of air. The air strainer must be properly
installedandkeptclean.Ifthecompressorintakeisconnected
to the engine air cleaner, supercharger, etc., these
connections must be properly installed and maintained.
Checkthecompressormountingstobesuretheyaresecure.
Checkthedriveforproperalignment, belt tension, etc.
Inspect the oil supply and return lines. Be sure these lines
areproperlyinstalled and thatthecompressor is gettingthe
proper supply of oil, and just as important, that the oil is
returningtotheengine. Checkthecoolantlinesto and from
the compressor and see that the cooling fins on the
crankcasearenotcloggedwith dirt, grease, etc.Checkthe
unloadermechanismfor properandpromptoperation.
OPERATING TESTS
Vehicles manufactured after the effective date of FMVSS
121,with theminimum requiredreservoirvolume,musthave
a compressor capable of raising air system pressure from
85-100 P.S.I. in 25 seconds or less. This test is performed
withthe engineoperatingatmaximumgovernedspeed.The
vehiclemanufacturermustcertify this performance onnew
vehicles with appropriate allowances for air systems with
greaterthanthe minimumrequiredreservoir volume.
AIR LEAKAGE TESTS
Leakage past the discharge valves can be detected by
removingthedischarge line,applyingshop airbackthrough
the discharge port and listening for escaping air. Also, the
dischargevalvesandthe unloader pistons canbechecked
forleakagebybuildinguptheairsystem until the governor
cutsout,thenstoppingthe engine.Withtheenginestopped,
listenforescapingair at the compressorintake.To pinpoint
leakage if noted, apply a small quantity of oil around the
unloader pistons. If there is no noticeable leakage at the
unloader pistons, the discharge valves may be leaking. If
the compressor does not function as described above, or
leakageisexcessive,itis recommended that itbereturned
to the nearest authorized Bendix Distributor for a factory
remanufactured compressor. If this is not possible, the
compressor can be repaired using genuine Bendix
replacementparts,inwhich case, the followinginformation
shouldprove helpful.
REMOVING AND DISASSEMBLY
REMOVING
These instructions are general and are intended to be a
guide,insomecasesadditionalpreparationsandprecautions
are necessary. Chock the wheels of the vehicle and drain
theairpressurefromallthe reservoirs in the system. Drain
the engine cooling system and the cylinder head of the
compressor. Disconnect all air, water and oil lines leading
to and from the compressor. Remove the drive gear(s) or
pulley from the compressor crankshaft using a gear puller.
Inspect the pulley or gear and associated parts for visible
wearordamage. Sincetheseparts areprecisionfitted,they
mustbereplacediftheyareworn or damaged.
DISASSEMBLY
GENERAL
Remove road dirt and grease from the exterior of the
compressorwitha cleaningsolvent.Before thecompressor
is disassembled, the following items should be marked to
showtheirrelationship whenthecompressoris assembled.
Mark both the front and rear end cover in relation to the
crankcase. Mark the drive end of the crankshaft in relation
tothefrontendcover and the crankcase.Markthecylinder
head in relation to the block and the block in relation to the
crankcase. Mark the base plate or base adapter in relation
to the crankcase.

7
Aconvenientmethod toindicatethe aboverelationshipisto
use a metal scribe to mark the parts with numbers or lines.
Do not use a marking method that can be wiped off or
obliterated during rebuilding, such as chalk. Remove all
compressor attachments such as governors, air strainers
or inlet fittings, discharge fittings and pipe plugs.
CYLINDER HEAD
Remove the six cylinder head cap screws (1) and tap the
head with a soft mallet to break the gasket seal. Remove
the inlet valve springs (2) and spring inserts (35) from the
head and inlet valves (3) from their guides in the block.
Remove inlet valve guides (4) from around the inlet valve
seats (34) on the block taking care not to damage seats.
Scrape off any gasket material (5) from the cylinder head
and block. Unscrew the discharge valve seats (6) from the
headandremovethedischargevalves (7) and springs (8).
Inspectthedischargevalveseats (2) for nicks, cracks,and
excessivewearandreplaceifnecessary.Thedischargevalve
cap/nutstops(9)shouldbe inspectedforwear andreplaced
ifexcessive peeninghas occurred.Todetermineifexcessive
peeninghasoccurred,measure the dischargevalvetravel.
Discharge valve travel must not exceed .046 inches. If
dischargevalvetravelisexcessive, replacethecapnut/stop
assembly,dischargevalve andspring.
Discard the inlet valves (3) and springs (2), the discharge
valves (7), springs (8) and the discharge valve seats (6) if
defective.
CRANKCASE BASE PLATE OR ADAPTER
Remove the cap screws securing the base plate or base
adapter. Tap with soft mallet to break the gasket seal (11).
Scrapeoffanygasket materialfromcrankcaseand plate or
adapter.
CONNECTING ROD ASSEMBLIES
(Note: Before removing the connecting rods, mark each
connectingrodand itscap.Each connectingrodis matched
to its own cap for proper bearing fit, and these parts must
notbeinterchanged.)Removetheconnecting rodbolts(13)
and bearing caps (14). Push the piston (15) with the
connectingrods(16) attached outthetop of thecylindersof
the cylinder block. Replace the bearing caps (14) on their
respective connecting rods. Remove the piston rings from
the pistons. If the pistons are to be removed from the
connectingrods,remove theteflonplugs (36)andpressthe
wrist pins (37) from the pistons and connecting rods.
FIGURE 8 - TU-FLO®700 AIR COMPRESSOR (THRU DRIVE) EXPLODED VIEW
34
35
36
28 REAR COVER
20
18
20
19
1819
6
78
9
1
5
23
4
CYLINDER BLOCK
16
17
CRANKSHAFT
14 13
26
FLANGE
ADAPTER
21
24
25
29 30
REAR COVER
GASKET
31
32
11
27 22
26
10
12
CYLINDER HEAD
37 33
23
34
35
15 36
37
CRANKCASE

8
Ifthepistonsareremovedfrom the rod, inspect the bronze
wrist pin bushing. Press out and replace the bushing if it is
excessivelyworn.(Seeinspectionofparts)Discardthepiston
rings(18-20)andtheconnectingrod journal bearings (17).
Discardthewristpinbushings (21) if they were removed.
CYLINDER BLOCK
Ifthecompressorisfittedwithan air strainer,inletelbowor
governorremove thesame.
Remove cap screws (23) securing cylinder block to the
crankcase;separatethecrankcaseandcylinderblock and
scrapeoffanygasketmaterial.
Remove the unloader spring (34), spring saddle (35), and
springseat(36) fromtheinletcavity ofthecrankcase,using
longnosepliers.With the useofshopairblow the unloader
plungers(37)andguides(33)outofthe cylinder block.
The inlet valve seats can be removed if worn or damaged
andarebeing replaced. Unloaderborebushingsshould be
inspected but not removed unless they are damaged. If
bushingsaretobereplaced,theycanberemovedbyrunning
a1/8"pipethreaded rod andpullingthebushing straight up
and out. Do not use "easy out" for removing the bushings.
CRANKCASE
Remove the key (22) or keys from the crankshaft and any
burrsonthecrankshaftwherethekeyorkeyswereremoved.
(Note: Throughdrivecompressorsmayhaveacrankshaft
keyatbothends.)Removethefourcapscrews(23)securing
frontordrive-endendcover or flange adapter. Remove the
endcover,takingcarenotto damagethecrankshaftoil seal
(27)or frontmainbearing(26),ifany.Removetheo-ring(24)
fromaroundthefrontendcover.Removethefourcapscrews
(30) securing the rear end cover and remove the rear end
covertakingcare nottodamagethe rearmainbearing(29),
ifany.Removetheo-ring (31) fromaroundtheendcover.If
the compressor has ball type main bearings, press the
crankshaftandballbearingsfrom thecrankcase,then press
theballbearingsfromthecrankshaft.
CLEANING OF PARTS
GENERAL
All parts should be cleaned in a good commercial grade
solventanddriedpriorto inspection.
CYLINDER HEAD
Removeallthe carbon depositsfromthedischarge cavities
and all the rust and scale from the cooling cavities of the
cylinder head body. Scrape all the foreign matter from the
body surfaces and use shop air pressure to blow the dirt
particles from all the cavities.
CYLINDER BLOCK
Clean the carbon and dirt from the inlet and unloader
passages. Use shop air pressure to blow the carbon and
dirtdepositsfromtheunloaderpassages.
OIL PASSAGES
Thoroughly clean all oil passages through the crankshaft,
crankcase, end covers, and base plate or base adapter.
Inspect the passages with a wire to be sure. Blow the
loosenedforeignmatteroutwith air pressure.
INSPECTION OF PARTS
CYLINDER HEAD BODY
Inspectthecylinder head forcracksordamage.Applyshop
air pressure to one of the coolant ports with all others
plugged,andcheck for leakagebyapplyinga soapsolution
to the exterior of the body. If leakage is detected, replace
thehead.
END COVERS
Check for cracks and external damage. If the crankshaft
main bearings are installed in the end cover, check for
excessivewear andflatspotsandreplacethem ifnecessary.
Ifthecompressorhasanoilsealintheendcover, it should
beremovedbypressingitout of the end cover.
CRANKCASE
Check all crankcase surfaces for cracks and damage. On
compressorswhereballbearingmainbearingsareusedthe
differencebetweentheO.D.of theouterraceandthe I.D.Of
the crankcase hole should be .0000 in. to .0015 in. loose.
Thisisto maintainthecorrectpress fit.Thecrankcasemust
be replaced if the fit is too loose.
Oncompressorsfittedwithprecision,sleevemainbearings,
the difference between the O.D. of the crankshaft journal
and the main bearing I.D. must not exceed .0065 in. If the
clearance is greater than .0065 in., the end cover or main
bearingmustbereplaced.
CYLINDER BLOCK
Check the unloader bore bushings to be sure they are not
worn, rusted, or damaged. If these bushings are to be
replaced, they can be removed by running a 1/8 in. pipe
thread tap into the bushing, and inserting a 1/8 in. pipe
threadedrodandpullingthebushingstraightup andout.Do
notusean easy-outforremoving thesebushings.Iftheinlet
valve seats are worn or damaged, so they cannot be
reclaimedby facing,theyshouldbereplaced.Cylinderbores
shouldbechecked with insidemicrometersorcalipers (see
Figure 9). Cylinder bores which are scored or out of round
by more than .001 in. or tapered more than .002 in. should

9
CRANKSHAFT
Checkthecrankshaftthreads,keyways,taperedends and
all machined and ground surfaces for wear, scores, or
damage.Standardcrankshaftjournalsare1.1250in.-1.1242
in. in diameter. If the crankshaft journals are excessively
scoredorwornor out ofroundandcannotbe reground, the
crankshaftmust bereplaced. Connectingrodbearinginserts
areavailablein.010 in., .020 in.and.030in.undersizes for
compressors with reground crankshafts. Main bearing
journalsmustbe maintainedsothe ballbearingsarea snug
fitor sothatnomorethan.0065in.clearanceexistsbetween
the precision sleeve main bearing and the main bearing
journalsonthecrankshaft. In crankshaftsfittedwithoilseal
rings,theoilsealringgrooveor grooves must not be worn.
Thering groovewallsmusthaveagoodfinish andtheymust
be square. Check to be sure the oil passages are open
throughthecrankshaft.
CONNECTING ROD BEARINGS
Usedbearinginsertsmustbereplaced.Connectingrodcaps
arenotinterchangeable. Thelockingslots oftheconnecting
rod and cap should be positioned adjacent to each other.
Clearance between the connecting journal and the
connecting rod bearing must not be less than .0003 in. or
morethan.0021in. after rebuilding.
bereboredorhonedoversize.Oversizedpistonsand piston
ringsareavailablein.010 in.,.020in.and.030 in.oversizes.
Cylinder bores must be smooth, straight, and round.
Clearancebetweenthe castironpistonsand cylinderbores
shouldbe between.002in.minimumand .004in.maximum.
FIGURE 9 - MEASURING CYLINDER BORES FIGURE 10 - CORRECT GROOVE CLEARANCE
.002"
.010"
END GAP
.000
.006
OIL RING
.002
.004
OIL RING
STANDARD
PISTON
RING
OIL RING
PISTON
RINGS
PISTON
RING
EXPANDER
RING
PISTONS
Check the pistons for scores, cracks, or enlarged ring
grooves; replace the pistons if any of these conditions are
found.Measureeach piston withamicrometerin relationto
thecylinderborediametertobesurethediametralclearance
is between .002 in. minimum and .004 in. maximum.
Checkthefitofthewrist pins to the pistonsandconnecting
rodbushings.Thewristpinshouldbealightpressfitinthe
piston. If the wrist pin is a loose fit, the piston and pin
assembly should be replaced. Check the fit of the wrist pin
in the connecting rod bushing by rocking the piston. This
clearanceshouldnot exceed.0007in. Replacethewristpin
bushingsifexcessiveclearanceis found.Wristpinbushings
should be reamed to between .5314 in. and .5317 in. after
beingpressedintotheconnectingrods.
Check the fit of the piston rings in the piston ring grooves.
Check the ring gap with the rings installed in the cylinder
bores. Refer to Figure 10 for correct gap and groove
clearances.

10
REPAIRS
DISCHARGE VALVES, VALVE STOPSAND
SEATS
Ifthe dischargevalve seatsmerelyshowsignsofslightwear,
they can be dressed by using a lapping stone, grinding
compoundand grindingtool. Installthenewdischargevalve
springs and valves. Screw in the discharge valve seats.
Dischargevalvetravelshouldbebetween.030in.to.046in.
Totestforleakagebythedischargevalves,apply100pounds
ofairpressurethroughthecylinderheaddischargeportand
apply a soap solution to the discharge valves and seats.A
slightleakageintheformofsoapbubbles is permissible. If
excessive leakage is found, leave the air pressure applied
andwiththeuseofafiberorhardwooddowelanda hammer,
tap the discharge valves off their seats several times. This
will help the valves to seat and should reduce the leakage.
With the air pressure still applied at the discharge port of
the cylinder head, check for leakage around the discharge
valve cap nut on the top of the cylinder head casting. No
leakageispermitted.
INLET VALVESAND SEATS
Inletvalvesandspringsshouldbereplaced,iftheinletvalve
seats show signs of slight nicks or scratches. They can be
redressedwitha finepieceofemery clothorby lappingwith
alappingstone, grindingcompoundandgrinding tool. Ifthe
seats are damaged to the extent that they cannot be
reclaimed,theymustbereplaced.Thedimension from the
top of the cylinder block to the inlet valve seat should not
exceed .113 in. nor be less than .101 in.
ASSEMBLY
General Note: All torques specified in this manual are
assembly torques and can be expected to fall off after
assembly is accomplished. Do not retorque after initial
assemblytorquesfall.
To convert inch pounds of torque to foot pounds of torque,
divideinchpoundsby12.
inch pounds ÷ 12 = foot pounds
To convert foot pounds of torque to inch pounds of torque,
multiply foot pounds by 12.
foot pounds x 12 = inch pounds
INSTALLING THE CRANKSHAFT
Pressnewsleeve bearingsinthe endcoverandcrankcase.
Ensure that the slot in the bearings line up with the oil
passagesin theendcoverorcrankcase.Ifyouhaveamodel
with no oil passage present in the crankcase, press the
sleeve bearing into the crankcase with the slot located 90
degreesfromvertical.
Install the front thrust washer with the tang inserted in the
slot toward the flange. Insert the crankshaft and the rear
thrustwasherwiththetangtowardtherearofthecompressor.
Placetheoilseal ring onthebossof the rear endcoverand
installtheendcovermakingsure not to pinch thesealring.
Ensure the tang of the thrust washer is inserted in the slot
oftheendcover.Fastenthe endcoverto thecrankcasewith
the four cover cap screws. Torque the cap screws to 175-
225 inch pounds in a cross pattern. Note: For cast iron
flange adapters, torque the four 7/16 in. cap screws to 38-
45 foot pounds. For die cast aluminum end covers, torque
the four 7/16 in. cap screws to 25-30 foot pounds. All end
coversusing5/16in.capscrewsorstudandnutsaretorqued
to15-18foot pounds. Forthroughdrivecompressors witha
cast iron end cover, torque the four 7/16 in. cap screws to
25-30footpounds.
PISTONS AND CONNECTING RODS
If new wrist pin bushings are to be used, they should be
pressed into the connecting rods so that the oil hole in the
bushinglinesupwiththeonein the rod. The new bushings
shouldthenbereamedor honed to provide between.0001
in. (.00254 mm) and .0006 in. (.01524 mm) clearance on
the wrist pin. Position the connecting rod in the piston and
press in the wrist pin.
Pistons installed in compressors manufactured prior to
November,1976,will havethewristpinsecuredinthe piston
byalock wire extendingthroughmatching holes inwristpin
and piston boss, anchored in a hole in the side wall of the
piston.Iftheoriginalpistonsareused the wrist pin must be
pressedinsotheholeinthewrist pin aligns with that of the
FIGURE 11 FIGURE 12
DISCHARGE VALVE,
VALVESTOP
AND SEAT INLET VALVE
AND SEAT
6
87
2
3
4
10

11
piston and secure same by inserting the new lockwire
throughtheholeinpiston and wrist pinandlockthewire by
snapping the short 90 section into the lockwire hole in the
bottom of the piston.
CompressorsbuiltafterNovember, 1976,willhave thewrist
pin secured by Teflon buttons in either end of the wrist pin,
allowing the wrist pin to float. The Teflon buttons pc. no.
292392 may be used with either new or old wrist pins. The
laterdesignpistonshavetworingsabovethewrist pin and
one below. Install the piston rings in the correct location
with the ring pipmarks up. Stagger the position of the ring
gaps. Prelubricate the piston, piston rings, wrist pins and
connectingrod.
CYLINDER BLOCK
Aligngasket(12), crankcase andcylinderblockand secure
withcap screws (23). Torque to 15-19 foot pounds.
UNLOADER
A new unloader kit should used when rebuilding. (Figure
13).(PieceNumber279615).Theunloaderpistonsinthekit
are prelubricated with a special lubricant piece number
239379andneednoadditionallubrication.Installtheunloader
pistons (28) in their bores being careful not to cut the
o-rings. Position the unloader plungers (37) in their guides
(38)andslip them inandoverthe topsofthepistons.Install
theunloader springseat (36)in thecylinderblockinletcavity;
a small hole is drilled in the cylinder block for this purpose.
Positionthesaddle(35)between theunloaderpistonguides
(38), so its forks are centered on the guides. Install the
unloader spring (34), making sure it seats over the spring
seats both in the block and on the saddle. Position and
installtheinletvalveguides(38),then droptheinletvalvesin
theirguides.Theinletvalvesshouldbe a loose sliding fit in
theguides.
36
34
38
35
28
FIGURE 13 - UNLOADER MECHANISM
37
CYLINDER HEAD
Installtheinletvalvesprings inthecylinderheadby applying
a turning motion to the spring after it is in the head. The
turning motion should dig the spring wire into the spring
seat in the bottom of the spring bore in the head. Should
thisprocedurefail after repeatedattempts,use a verysmall
quantity of grease to hold them in place, just enough to
keep the springs from falling out. Place the cylinder head
gasket on the cylinder block. Carefully align the cylinder
head assembly on the block and install the cap screws,
tighteningthemevenlytoa torque of 15-19footpounds.
BASE PLATE OR BASEADAPTER
Position the base plate or base adapter gasket on the
crankcase and install the base plate or base adapter as
marked before disassembly. Tighten the six cap screws
securingthecastironbaseadapterevenlytoatorqueof38-
45 foot pounds, and 12-16 foot pounds for base plate or
aluminumcover.
TESTING REBUILT COMPRESSOR
In order to properly test a compressor under operating
conditions, a test rack for correct mounting, cooling,
lubricating,anddrivingthecompressoris necessary. Such
testsarenotcompulsoryiftheunithasbeencarefullyrebuilt
byanexperiencedperson.Acompressor efficiencyorbuild-
up test can be run which is not too difficult. An engine
lubricated compressor must be connected to an oil supply
line of at least 15 P.S.I. pressure during the test and an oil
returnlinemustbe installedtokeepthecrankcase drained.
Connecttothecompressor discharge port, areservoirwith
a volume of 1500 cubic inches, including the volume of
connecting line. With the compressor operating at 2100
R.P.M.,thetimerequiredtoraisethereservoir(s)pressure
from 85 P.S.I. to 100 P.S.I. should not exceed 7 seconds.
During this test, the compressor should be checked for
gasket leakage and noisy operation, as well as unloader
operationandleakage.
INSPECTION OF REBUILT UNIT
Check to be sure that covers, plugs, or masking tape are
used to protect all ports if compressor is not to be installed
immediately. Fit the end of all crankshafts with keys, nuts,
andcotter pinsas requiredandthenprotecttheendsagainst
damagebywrapping withmaskingtape orfrictiontape. The
open bottom of a vertical engine lubricated compressors
should be protected against the entrance of dirt during
handlingorstorage,byinstallingatemporarycover overthe
base.

12
COMPRESSOR TROUBLESHOOTING
IMPORTANT:Thetroubleshootingcontainedinthis section
considers the compressor as an integrated component of
theoverallairbrakechargingsystem and assumes that an
airdryerisin use. Thetroubleshootingpresentedwillcover
notonlythecompressoritself,butalsootherchargingsystem
devices as they relate to the compressor.
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
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. Useonlythepropertoolsandobserve
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™airdryersystemoradryerreservoirmodule,
be sure to drain the purge reservoir.
5. Following the vehicle manufacturer’s
recommendedprocedures,deactivatetheelectrical
systeminamannerthatsafelyremovesallelectrical
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
bedesignedspecificallyforsuchapplicationsand
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
notattemptrepairsrequiringmachiningorwelding
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.
11. ForvehicleswithAntilock TractionControl (ATC),
the ATC function must be disabled (ATC indicator
lampshouldbeON)priortoperforminganyvehicle
maintenance where one or more wheels on a
drive axle are lifted off the ground and moving.
TABULATED DATA
Numberofcylinders ............................ 2
Bore size ............................................ 2.75 in.
Stroke ................................................. 1.81 in.
Piston displacement at 1250 RPM ...... 15.5 cu. ft.
MaximumrecommendedRPM
(naturallyaspirated)............................. 3000
Minimum coolant flow at maximum
RPM ................................................... 2.5 gal./min.
Recommendedminimum
discharge line size .............................. 5/8 in. OD
CopperTube
Recommendedminimumoil
return line size .................................... 5/8in.ODTubing
Recommendedminimumoil
supply line size ................................... 1/4in. OD Tubing
Recommendedminimumunloader
line size .............................................. 1/4 in.ODTubing
Recommendedminimumcoolant
line size .............................................. 1/2 in.ODTubing
Recommendedmaximuminlet
airtemperature.................................... 250°F
Recommendedmaximum
dischargeairtemperature.................... 400°F
Minimumpressurerequired
tounload ............................................. 60PSI

*This guide is only for vehicles that use desiccant air dryers.
The guide consists of an introduction to air brake charging system
components, a table showing recommended vehicle maintenance
schedules, and a troubleshooting symptom and remedy section with tests
to diagnose most charging system problems.
Advanced Troubleshooting Guide
for Air Brake Compressors*
This troubleshooting guide obsoletes and supersedes all previous published
troubleshooting information relative to Bendix air compressors.
Air brake charging system:
Slow build (9.0) . . . . . . . . . . . . . . . . . 21 - 22
Doesn’t build air (10.0) . . . . . . . . . . . . . . . 23
Air dryer:
Doesn’t purge (14.0) . . . . . . . . . . . . . . . . . 24
Safety valve releases air (12.0). . . . . . . . . 24
Compressor:
Constantly cycles (15.0) . . . . . . . . . . . . . . 24
Leaks air (16.0) . . . . . . . . . . . . . . . . . . . . . 25
Safety valve releases air (11.0). . . . . . . . . 23
Noisy (18.0) . . . . . . . . . . . . . . . . . . . . . . . . 25
Reservoir:
Safety valve releases air (13.0). . . . . . . . . 24
INDEX
Air Coolant
Engine
Oil
Compressor leaks coolant (17.0) . . . . . . . . . . 25
Oil consumption (6.0) . . . . . . . . . . . . . . . . . . . 21
Oil Test Card results (1.0) . . . . . . . . . . . . . . . . 16
Oil is present:
On the outside of the compressor (2.0). . . 17
At the air dryer purge/exhaust
or surrounding area (3.0) . . . . . . . . . . . 17
In the supply reservoir (4.0). . . . . . . . 18 - 20
At the valves (5.0) . . . . . . . . . . . . . . . . . . . 20
At air dryer cartridge (7.0) . . . . . . . . . . . . . 21
In the ping tank or compressor
discharge aftercooler (8.0) . . . . . . . . . . 21
Symptom Page Number
(1) Oil Leakage at Head Gasket . . .26
(2) System Leakage . . . . . . . . . . . .26
(3) Compressor Discharge and
Air Dryer Inlet Temperature . . . .26
(4) Governor Malfunction . . . . . . . .27
(5) Governor Control Line . . . . . . . .27
(6) Compressor Unloader . . . . . . . .27
BASIC Test Information . . . . . . 28-30
Test Procedures
Maintenance Schedule and
Usage Guidelines (Table A) . . 15
Symptom Page Number
Maintenance & Usage Guidelines
13

14
Introduction to the Air Brake Charging System
Powered by the vehicle engine, the air compressor
builds the air pressure for the air brake system. The
aircompressoristypically cooled by theenginecoolant
system and lubricated by the engine oil supply.
The compressor's unloader mechanism and governor
(along with a synchro valve for the Bendix®DuraFlo™
596 air compressor) control the brake system air
pressure between a preset maximum and minimum
pressurelevelbymonitoring the pressureintheservice
(or“supply”)reservoir. Whentheairpressure becomes
greater than that of the preset “cut-out”, the governor
controls the unloader mechanism of the compressor
to stop the compressor from building air and also
causes the air dryer to purge. As the service reservoir
airpressuredropstothe“cut-in” settingofthegovernor,
the governor returns the compressor back to building
air and the air dryer to air drying mode.
As the atmospheric air is compressed, all the water
vapor originally in the air is carried along into the air
system, as well as a small amount of the lubricating oil
as vapor.
The duty cycle is the ratio of time the compressor
spends building air to the total engine running time.
Aircompressorsaredesigned to buildair(run“loaded”)
up to 25% of the time. Higher duty cycles cause
conditions that affect air brake charging system
performance which may require additional
maintenance. Factors that add to the duty cycle are:
air suspension, additional air accessories, use of an
undersized compressor, frequent stops, excessive
leakage from fittings, connections, lines, chambers or
valves, etc.
The discharge line allows the air, water-vapor and
oil-vapor mixture to cool between the compressor and
air dryer. The typical size of a vehicle's discharge line,
(see column 2 of Table A on page 15) assumes a
compressor with a normal (less than 25%) duty cycle,
operating in a temperate climate. See Bendix and/or
other air dryer manufacturer guidelines as needed.
Whenthe temperatureof thecompressed airthatenters
the air dryer is within the normal range, the air dryer can
remove most of the charging system oil. If the
temperature of the compressed air is above the normal
range, oil as oil-vapor is able to pass through the air
dryerandinto theairsystem. Larger diameterdischarge
linesand/orlongerdischargelinelengthscanhelpreduce
the temperature.
The discharge line must maintain a constant slope
down from the compressor to the air dryer inlet fitting
to avoid low points where ice may form and block the
flow. If, instead, ice blockages occur at the air dryer
inlet, insulation may be added here, or if the inlet fitting
is a typical 90 degree fitting, it may be changed to a
straight or 45 degree fitting. For more information on
how to help prevent discharge line freeze-ups, see
Bendix Bulletins TCH-08-21 and TCH-08-22 (see
pages 31-33). Shorter discharge line lengths or
insulation may be required in cold climates.
The air dryer contains a filter that collects oil droplets,
and a desiccant bed that removes almost all of the
remaining water vapor. The compressed air is then
passed to the air brake service (supply) reservoir. The
oil droplets and the water collected are automatically
purgedwhenthegovernorreachesits “cut-out” setting.
Forvehicleswithaccessories that aresensitivetosmall
amounts of oil, we recommended installation of a
Bendix®PuraGuard®system filter, designedtominimize
the amount of oil present.
Air Dryer
Reservoir Drain
Service Reservoir
(Supply Reservoir)
Compressor
Governor
(Governor plus Synchro valve
for the Bendix®DuraFlo™596™
Compressor)
Discharge
Line Optional “Ping” Tank
Optional Bendix®PuraGuard®
System Filter or PuraGuard®
QC™Oil Coalescing Filter
The Air Brake Charging System supplies the
compressed air for the braking system as well as other
air accessories for the vehicle. The system usually
consists of an air compressor, governor, discharge line,
air dryer, and service reservoir.

15
Compressor with up to 25% duty cycle
Footnotes:
1 With increased air demand the air dryer cartridge needs to be replaced more often.
2 Use the drain valves to slowly drain all reservoirs to zero psi.
3 Allow the oil/water mixture to fully settle before measuring oil quantity.
4 Tocounterabovenormaltemperaturesat the air dryerinlet,(andresultantoil-vapor passing
upstream in the air system) replace the discharge line with one of a larger diameter and/
or longer length. This helps reduce the air's temperature. If sufficient cooling occurs, the
oil-vaporcondensesand can beremovedbytheairdryer. Dischargelineupgradesarenot
coveredunderwarranty. Note:Tohelppreventdischargeline freeze-ups,shorterdischarge
linelengths orinsulationmay berequiredin coldclimates. (SeeBendixBulletinsTCH-08-21
and TCH-08-22, included inAppendix B, for more information.)
5 For certain vehicles/applications, where turbo-charged inlet air is used, a smaller size
compressor may be permissible.
Recom- Recom- Acceptable
Typical Discharge mended mended Reservoir
Compressors Line Air Dryer Reservoir Oil Contents3
No. of Spec'd Cartridge Drain at Regular
Axles Replacement1Schedule2Drain Interval
High Air Use
Low Air Use
e.g. Double/triple trailer, open
highway coach/RV, (most)
pick-up & delivery, yard or
terminal jockey, off-highway,
construction, loggers, concrete
mixer, dump truck, fire truck.
e.g. Line haul single trailer
w/o air suspension, air over
hydraulic brakes.
e.g. Line haul single trailer
with air suspension,
school bus.
e.g. City transit bus, refuse,
bulk unloaders, low boys,
urban region coach, central
tire inflation.
5
or
less
5
or
less
8
or
less
12
or
less
Table A: Maintenance Schedule and Usage Guidelines
Recom-
mended
Every
Month -
Max of
every 90
days
Every
Month
Every 3
Years
Every 2
Years
Every
Year
I.D.
Vehicle Used for:
Column 1 Column 2 Column 3 Column 4 Column 5
Regularly scheduled maintenance is the single most important factor in maintaining the air brake charging system.
Note: Compressor and/or air dryer
upgradesare recommended incases
where duty cycle is greater than the
normal range (for the examples
above).
For Bendix®Tu-Flo®550 and 750
compressors, unloader service is
recommended every 250,000 miles.
Length
6 ft.
1/2 in.
9 ft.1/2 in.
12 ft.
1/2 in.
5/8 in. 12 ft.
BASIC test
acceptable
range:
5 oil units
per month.
See
appendix
A.
For oil carry-over
control4 suggested
upgrades:
3/4 in. 15 ft.
For oil carry-over
control4 suggested
upgrades:
5/8 in. 15 ft.
For oil carry-over
control4 suggested
upgrades:
5/8 in. 9 ft.
For oil carry-over
control4 suggested
upgrades:
5/8 in. 12 ft.
Compressor with less than 15% duty
cycle
Compressor with up to 25% duty cycle
Compressor with up to 25% duty cycle
Bendix®BA-921™air compressor
Bendix®Tu-Flo®550 air compressor
Bendix®Tu-Flo®750 air compressor
Bendix®BA-922™, or DuraFlo™596air compressor
BASIC test
acceptable
range:
3 oil units
per month.
See
appendix
A.
For the
BASIC
Test Kit:
Order
Bendix
P/N
5013711

16
ü
Air Brake Charging System Troubleshooting
How to use this guide:
1.0 Oil Test Card
Results Not a valid test. Discontinue using this test.
Do not use this card test to diagnose
compressor "oil passing" issues. They are
subjective and error prone. Use only the
BendixAirSystemInspectionCup (BASIC)test
and the methods described in this guide for
advanced troubleshooting.
The Bendix®BASIC test should be the
definitive method for judging excessive oil
fouling/oil passing. (See Appendix A, on
page 28 for a flowchart and expanded
explanation of the checklist used when
conducting the BASIC test.)
Symptom: What it may indicate: What you should do:
Find the symptom(s) that you see, then move to the right to
find the possible causes (“What it may indicate”) and
remedies (“What you should do”).
Review the warranty policy before performing any intrusive
compressor maintenance. Unloader or cylinder head gasket
replacement and resealing of the bottom cover plate are
usually permitted under warranty. Follow all standard safety
procedures when performing any maintenance.
Look for:
Normal - Charging system is working within
normal range.
Check - Charging system needs further
investigation.
û
Bendix®
BASIC Test
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 shouldbe shut offandthe ignition
keyshould be removed. Wherecircumstancesrequirethat
the engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from contact
withmoving,rotating,leaking, heated or electrically charged
components.
3. Donot 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.
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 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.Neverremove a componentorplug
unless you are certain all system pressure has been
depleted.
8. Useonly genuine Bendix®replacement parts,components
andkits.Replacementhardware, 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 certain all
components and systems are restored to their proper
operating condition.
11. For vehicles withAntilock Traction Control (ATC), theATC
function must be disabled (ATC indicator lamp should be
ON) prior to performing any vehicle maintenance where
oneor more wheels onadriveaxle are lifted offthe ground
and moving.

Symptom: What it may indicate: What you should do:
17
2.2 Oil leaking
from compressor: (a)Excessive leak at head gasket.
(b)Leak at bottom cover plate.
(c)Leak at internal rear flange gasket.
(d)Leak through crankcase.
(e)(If unable to tell source of leak.)
ðGo to Test 1 on page 26.
ðReseal bottom cover plate using RTV
silicone sealant.
ðReplace compressor.
ðReplace compressor.
ðClean compressor and check periodically.
Air brake charging system functioning
normally.
ðAir dryers remove water and oil from the
air brake charging system.
Check that regular maintenance is being
performed. Return the vehicle to service.
An optional kit (Bendix piece number
5011327 for the Bendix®AD-IS™orAD-IP™
air dryers, or 5003838 for the Bendix®
AD-9™air dryer) is available to redirect the
air dryer exhaust.
3.0 Oil at air dryer
purge/exhaust or
surrounding area
(c)
2.0 Oil on the
Outside of the
Compressor
Find the source and repair. Return the vehicle
to service.
ðRepair or replace as necessary. If the
mounting bolt torques are low, replace the
gasket.
ðReplace the fitting gasket. Inspect inlet
hose and replace as necessary.
ðReplace gasket or fitting as necessary to
ensure good seal.
ðInspect and repair as necessary.
Engine and/or other accessories
leaking onto compressor.
(a)Leak at the front or rear (fuel
pump, etc.) mounting flange.
(b)Leak at air inlet fitting.
(c)Leak at air discharge fitting.
(d)Loose/broken oil line fittings.
2.1 Oil leaking at
compressor / engine
connections:
(a)
ð
ð
Head
gasket
and rear
flange
gasket
locations.
(c)

18
4.0 Oil in Supply or
Service Reservoir
(air dryer installed)
(If a maintained Bendix®
PuraGuard®system filter
or Bendix®PuraGuard®
QC™oil coalescing filter
is installed, call
1-800-AIR-BRAKE
(1-800-247-2725) and
speak to a Tech Team
member.)
(a)If air brake charging system
maintenance has not been
performed.
Thatis,reservoir(s)have not been
drained per the schedule in Table
Aonpage15,Column 4 and/or the
air dryer maintenance has not
been performed as in Column 3.
(b)If the vehicle maintenance has
been performed as recom-
mended in Table A on page 15,
someoilinthe reservoirsisnormal.
ðDrainallairtanksand check vehicle atnext
service interval using the Bendix®BASIC
test. See Table A on page 15, column 3
and4,forrecommendedserviceschedule.
ðDrain all air tanks into Bendix®BASIC test
cup (Bendix Air System Inspection Cup).
If less than one unit of reservoir contents
is found, the vehicle can be returned to
service. Note: If more than one oil unit
of water (or a cloudy emulsion mixture)
is present, change the vehicle's air
dryer, check for air system leakage (Test
2, on page 26), stop inspection and
check again at the next service interval.
See the BASIC test kit for full details.
If less than one "oil unit" of water (or water/
cloudy emulsion mixture) is present, use
the BASIC cup chart on the label of the
cup to determine if the amount of oil found
is within the acceptable level.
ðIf within the normal range, return the
vehicle to service. For vehicles with
accessories that are sensitive to small
amounts of oil, consider a Bendix®
PuraGuard®QC™oil coalescing filter.
ðIf outside the normal range go to
Symptom 4.0(c).
Also see the Table A on page 15, column
3 for recommended air dryer cartridge
replacement schedule.
Maintenance
(a)
ðGo to Test 2 on page 26.
ðSee Table A, column 1, on page 15 for
recommended compressor sizes.
ðIf the compressor is "too small" for
the vehicle's role (for example, where a
vehicle's use has changed or service
conditions exceed the original vehicle or
engine OE spec's) then upgrade the
compressor. Note: Thecosts incurred(e.g.
installing a larger capacity compressor,
etc.) are not covered under original
compressor warranty.
ðIf the compressor is correct for the
vehicle, go to Symptom 4.0 (e).
Duty cycle too high
Symptom: What it may indicate: What you should do:
See Table A, on page 15,
for maintenance
schedule information.
Drain all air tanks (reservoirs)
into the Bendix®BASIC test
cup. (Bendix kit P/N 5013711).
The duty cycle is the ratio of time the compressor spends
building air to total engine running time. Air compressors
are designed to build air (to "run loaded") up to 25% of the
time. Higher duty cycles cause conditions that affect air
brake charging system performance which may require
additional maintenance. Factors that add to the duty cycle
are: air suspension, additional air accessories, use of an
undersized compressor, frequent stops, excessive leakage
from fittings, connections, lines, chambers or valves, etc.
(c)Air brake system leakage.
(d)Compressormaybeundersized for
the application.

Symptom: What it may indicate: What you should do:
19
(e)Air compressor discharge and/or
airdryerinlettemperaturetoo high.
(f) Insufficient coolant flow.
(g)Restricted discharge line.
ðCheck temperature as outlined in Test 3
on page 26. If temperatures are normal
go to 4.0(h).
ðInspectcoolantline.Replaceasnecessary
(I.D. is 1/2").
ðInspect the coolant lines for kinks and
restrictions and fittings for restrictions.
Replace as necessary.
ðVerify coolant lines go from engine block
tocompressorandback to the waterpump.
Repair as necessary.
ðIf discharge line is restricted or more than
1/16" carbon build up is found, replace the
discharge line. SeeTable A, column 2, on
page 15 for recommended size. Replace
as necessary.
ðThe discharge line must maintain a
constant slope down fromthecompressor
to the air dryer inlet fitting to avoid low
points where ice may form and block the
flow. If, instead, ice blockages occur at the
air dryer inlet, insulation may be added
here, or if the inlet fitting is a typical 90
degree fitting, it may be changed to a
straight or 45 degree fitting. For more
informationonhowtohelppreventdischarge
line freeze-ups, see Bendix Bulletins
TCH-08-21 and TCH-08-22 (Appendix B).
Shorter discharge line lengths or insulation
may be required in cold climates.
Temperature
Other
ðCheck compressor air inlet line for
restrictions, brittleness, soft or sagging
hoseconditions etc. Repair as necessary.
Inlet line size is 3/4 ID. Maximum
restriction requirement for compressors is
25 inches of water.
ðCheck the engine air filter and service if
necessary (if possible, check the air filter
usage indicator).
(h)Restricted air inlet (not enough air
to compressor).
(g)
(h)
4.0 Oil in Supply
or Service
Reservoir*
(air dryer installed)
(continued)
(f)
(e)
(g)
Kinked discharge line shown.
Partly
collapsed
inlet line
shown.
Testing the temperature
at the discharge fitting. Inspecting the coolant hoses.
*If a maintained Bendix®PuraGuard®system filter or Bendix®PuraGuard®QC™oil coalescing
filter is installed, call 1-800-AIR-BRAKE (1-800-247-2725) and speak to a Tech Team
member.

Symptom: What it may indicate: What you should do:
20
(i) Poorly filtered inlet air (poor air
quality to compressor).
(j) Governor malfunction or setting.
(k)Compressor malfunction.
4.0 Oil in Supply
or Service
Reservoir*
(air dryer installed)
(continued)
ðCheck for leaking, damaged or defective
compressor air inlet components (e.g.
inductionline,fittings,gaskets,filterbodies,
etc.). Repair inlet components as needed.
Note: Dirt ingestion will damage
compressor and is not covered under
warranty.
ðGo to Test 4 on page 27.
ðIf you found excessive oil present in the
service reservoir in step 4.0 (b) above and
you did not find any issues in steps 4.0 (c)
through 4.0 (j) above, the compressor may
be passing oil.
Replace compressor. If still under
warranty, follow normal warranty process.
Note: After replacing a compressor,
residual oil may take a considerable period
of time to be flushed from the air brake
system.
Other (cont.)
Inspect the
engine air
cleaner.
** SAE J2024 outlinestestsall airbrake systempneumatic
componentsneedto beableto pass,including minimum
levels of tolerance to contamination.
5.0 Oil present at
valves (e.g. at
exhaust, or seen
during servicing).
Air brake system valves are required
to tolerate a light coating of oil. ðA small amount of oil does not affect SAE
J2024** compliant valves.
ðCheck that regular maintenance is being
performed and that the amount of oil in the
air tanks (reservoirs) is within the
acceptable range shown on the Bendix®
BASICtestcup(seealsocolumn5ofTable
A on page 15). Return the vehicle to
service.
For oil-sensitive systems, see page 14.
Genuine
Bendix
valves are
all SAE
J2024
compliant.
*If a maintained Bendix®PuraGuard®system filter or Bendix®PuraGuard®QC™oil coalescing
filter is installed, call 1-800-AIR-BRAKE (1-800-247-2725) and speak to a Tech Team
member.
Crankcase Flooding
Consider installing a compressor bottom drain kit
(where available) in cases of chronic oil passing
where all other operating conditions have been
investigated. Bendix compressors are designed to
have a 'dry' sump and the presence of excess oil in
the crankcase can lead to oil carryover.