BENDIX TU-FLO 600 AIR COMPRESSOR User manual

1
®
Bendix®TU-FLO®600 Air Compressor
SD-01-336
GENERAL
Thefunctionoftheaircompressoristobuildupandmaintain
theair pressurerequired tooperate airpowered devicesin
air brake or air auxiliary systems.
DESCRIPTION
TheTu-Flo®600 compressorisa twocylinderreciprocating
singlestage compressorwith arated displacementof 14.5
cfm at 1250 rpm.
TheTu-Flo®600compressorisconstructedwithacrankcase,
block, and head assembly. The crankcase assemblies, in
particular,areessentially thesameascorrespondingTu-Flo®
500compressors.The blockassemblyincludes theairinlet
cavity, automatic inlet valves and unloader valves. Vertical
mountingpads forgovernor mountingare includedat each
endoftheblock.The headassembly includesthedischarge
valves with discharge ports either on the side or top of the
block.
All Tu-Flo®600 compressors are liquid cooled, both head
and block, by coolant from the engine cooling system.
Various mounting and drive configurations are used as
requiredbydifferentvehicleand engine designs.SeeFig.1.
AllTu-Flo®600compressorsreceiveoilunderpressurefrom
the engine lubricating system for the lubrication of the
internal parts. Fig. 2 shows a cross section of a typical
Tu-Flo®600compressor andthe oilflow therein.
Oil is forced through the oil passage in the crankshaft to
eachconnectingrod journal.Oilis forcedoutat thejournals
andis thrownby centrifugal forceagainst thecylinder walls
and crankshaft main bearings, providing lubrication.
The wrist pins and wrist pin bushings are lubricated in two
ways depending on the type connecting rod used. Some
oldercompressors,andone currentdesignuseforgedsteel
rifle drilled rods, through which oil is forced to the wrist pin
bushings. Standard current design consists of a diecast
aluminum or forged steel rod with an “oil catch-funnel” at
the top of the rod and a short hole connecting to the wrist
pin bushing. See Fig. 3.
TU-FLO®600 AIR COMPRESSOR VERTICAL MOUNT TU-FLO®600 AIR COMPRESSOR FLANGE MOUNT

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FIGURE 2 - TU-FLO®600AIR COMPRESSOR SECTIONAL
VIEW
FIGURE 3 - TU-FLO®600AIR COMPRESSOR PISTON/PIN
DESIGN
FIGURE1 -FLANGE CONFIGURATIONS
WRIST
PIN
BUSHING
WRIST
PIN
OILPASSAGE
WRIST
PIN
BUSHING
PISTON WRIST
PIN LOCK WIRE
CAST IRON
PISTON
STEEL
CONNECTING
ROD
“CATCH FUNNEL”
TEFLON
PLUG
DIE
CAST
PISTON
DIECAST
CONNECTING
ROD
NAME PLATE
A name plate is attached to the crankcase of all
compressors. It shows the piece number, type and serial
number (Fig. 4). A name plate with a black background
denotes a new compressor, whereas a name plate with a
redbackgrounddesignates thatthecompressoris afactory
reconditionedunit.Allcompressorsareidentifiedbythepiece
number which is the number to be used when reference is
madetoa particularcompressor.Thetypeandserialnumber
issupplementary information.
OLD DESIGN NEWDESIGN

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FIGURE 5
FIGURE 6
DISCHARGE
VALVE
PISTON
STROKE
TO GOVERNOR
INTAKE
STRAINER
UNLOADER
PLUNGER
INLETVALVE
TO RESERVOIR
INTAKE
DISCHARGE
VALVE
PISTON
STROKE
TO GOVERNOR
INTAKE
STRAINER
UNLOADER
PLUNGER
INLETVALVE
TO RESERVOIR
COMPRESSION
FIGURE 7
DISCHARGE
VALVE
PISTON
STROKE
TO GOVERNOR
INTAKE
STRAINER
UNLOADER
PLUNGER
TO RESERVOIR
UNLOADING
INLETVALVE
FIGURE 4
OPERATION
GENERAL
All compressors run continuously while the engine is
running, but actual compression of air is controlled by a
governor which stops or starts the compression of air by
loadingor unloadingthe compressorin conjunctionwith its
unloading mechanism. This is done when the air pressure
in the system reaches the desired maximum or minimum
pressures.
INTAKEANDCOMPRESSION (LOADED)
Duringthedownstrokeofthepiston,aslightvacuumcreated
abovethe pistoncauses theinlet valveto move offits seat.
Atmosphericair isdrawnin throughthecompressor intake,
bythe openinlet valve,and on top of the piston (Fig.5). As
thepiston startsitsupward stroke,the air thatwas drawnin
onthedown strokeisbeing compressed.Now,airpressure
on top of the inlet valve plus the force of its spring, returns
the inlet valve to its seat. The piston continues the upward
strokeand compressesthe airsufficiently toovercome the
dischargevalvespring and unseatthedischargevalve. The
compressed air then flows past the open discharge valve,
into the discharge line and on to the reservoirs (Fig. 6).
Asthe pistonreaches the top of itsstroke andstarts down,
thedischargevalve springreturnsthe dischargevalveto its
seat. This prevents the compressed air in the discharge
line from returning to the cylinder bore as the intake and
compression cycle is repeated.
NON-COMPRESSION(UNLOADED)
When the air pressure in the reservoir reaches the high
pressure setting of the governor, the governor opens,
allowingair to passfrom thereservoirthrough thegovernor
and into the cavity beneath the unloader pistons. This lifts
the unloader pistons and plungers. The plungers move up
and hold the inlet valves off their seats (Fig. 7).
With the inlet valves held off their seats by the unloader
pistons and plungers, air is merely pumped back and forth
between the two cylinders. When air is used from the
reservoirand thepressure dropsto low pressure setting of
thegovernor,thegovernor closesand in doingso exhausts
the air from beneath the unloader pistons. The unloader
saddlespringforces thesaddle,pistonsand plungersdown
and the inlet valves return to their seats. Compression is
thenresumed.

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COMPRESSOR & THE AIR BRAKE SYSTEM
GENERAL
The compressor is part of the total air brake system, more
specifically,the chargingportionof theairbrake system.As
acomponent inthe overallsystem its condition,duty cycle,
proper installation and operation will directly affect other
components in the system.
Powered by the vehicle engine, the air compressor builds
theairpressurefortheairbrakesystem.Theair compressor
istypically cooledby theengine coolantsystem, 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
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
buildingairtothe totalengine running 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, excessiveleakage
from fittings, connections, lines, chambers or valves, etc.
RefertoTableAin theTroubleshootingsectionfor aguideto
variousdutycyclesandtheconsiderationthatmustbe given
tomaintenance ofother components.
COMPRESSORINSTALLATION
While the original compressor installation is usually
completed by the vehicle manufacturer, conditions of
operation and maintenance may require additional
consideration.The following presentsbase guidelines.
DISCHARGELINE
Thedischarge line allowsthe air,water-vapor andoil-vapor
mixture to cool between the compressor and air dryer or
reservoir.The typical sizeof a vehicle'sdischarge line, (see
column2ofTableAintheTroubleshootingsection) assumes
a compressor with a normal (less than 25%) duty cycle,
operating in a temperate climate. See Bendix and/or other
airdryer manufacturer guidelinesas needed.
The discharge line must maintain a constant slope down
fromthe compressorto theair dryerinlet fittingor reservoir
toavoidlowpointswhereicemay formandblocktheflow. If,
instead, ice blockages occur at the air dryer or reservoir
inlet,insulation may beadded here,or if theinlet fittingis a
typical 90 degree fitting, it may be changed to a straight or
45degreefitting.Shorterdischargeline lengths orinsulation
may be required in cold climates.
While not all compressors and charging systems are
equippedwith adischargeline safetyvalvethis component
isrecommended.Thedischargelinesafetyvalve is installed
in the cylinder head or close to the compressor discharge
portand protects againstover pressurizing thecompressor
inthe eventof adischarge line freezeup.
FIGURE 8A - 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™
OilCoalescing Filter
The Air Brake Charging System supplies the
compressedair for thebraking systemaswell asotherair
accessories for the vehicle. The system usually consists
of an air compressor, governor, discharge line, air dryer,
andservicereservoir.

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DISCHARGELINE TEMPERATURE
When the temperature of the compressed air that enters
the air dryer is within the normal range, the air dryer can
removemost ofthe chargingsystem oil. If the temperature
ofthe compressed air is abovethe normalrange, oil as oil-
vapor is able to pass through the air dryer and into the air
system. Larger diameter discharge lines and/or longer
dischargeline lengthscan helpreduce thetemperature.
Theair dryer containsa filter thatcollects oil droplets,and a
desiccantbedthatremovesalmostalloftheremainingwater
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™oilcoalescing filter,designed tominimize
the amount of oil present.
AIR CLEANER MAINTENANCE
POLYURETHANESPONGE STRAINER (FIG. 9)
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
engineoilthensqueezeddrybeforereplacingitinthestrainer.
Be sure to replace the air strainer gasket if the entire air
straineris removedfrom thecompressor intake.
DRY ELEMENT - PLEATED PAPER AIR STRAINER
(FIG. 10)
Removethe springclips from eitherside ofmounting baffle
andremove thecover.Replace the pleatedpaperfilter and
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:Somecompressorsarefittedwithcompressorintake
adapters(Fig. 11) whichallow thecompressor intaketo be
connectedto theengine aircleaner.
In this case, the compressor receives a supply of clean air
from the engine air cleaner. When the engine air filter is
changed,thecompressor intakeadaptershouldbechecked.
If it is loose, remove the intake adapter, clean the strainer
plate, if applicable, and replace the intake adapter gasket,
and reinstall the adapter securely. Check line connections
bothat the compressorintake adapterandat theengineair
cleaner.Inspect the connectinglineforrupturesand replace
it if necessary.
FIGURE 9 - SPONGE TYPE STRAINER
FIGURE 10 - DRY ELEMENT STRAINER
FIGURE 8B - DISCHARGE LINE SAFETY VALVE
HOLE
THREAD

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AIR LEAKAGE TESTS
Leakage past the discharge valves can be detected by
removingthedischargeline, applyingshopairback through
the discharge port and listening for escaping air. Also, the
dischargevalves andthe unloader pistonscan bechecked
forleakage bybuilding up the air systemuntil thegovernor
cutsout,thenstoppingthe engine. Withtheenginestopped,
carefully listen for escaping air at the intake. To pin-point
leakage if noted, squirt oil around the unloader pistons. If
there is no noticeable leakage at the unloader pistons, the
dischargevalves maybe leaking.
Ifthe compressordoes notfunctionas describedabove, or
leakageis excessive,it isrecommendedthat itbe returned
to the nearest Bendix authorized distributor for a factory
rebuiltcompressorunder therepairexchange plan.Ifthis is
notpossible, thecompressor canbe repairedwith genuine
Bendix partsinwhich case thefollowinginformation should
provehelpful.
REMOVING AND INSTALLING
REMOVING
Theseinstructionsaregeneralandinsomecases additional
precautionsmust betaken.
Drain air brake system.
Drainenginecoolingsystem,compressorcylinderhead and
block.
Disconnect all air lines, water and oil lines to and from
compressor.
Removecompressor mountingbolts andcompressor from
engine.
Use a gear-puller to remove the gear or pulley from
compressorcrankshaft.
INSTALLATION
Clean oil supply line. Before connecting this line to the
compressor run the engine briefly to be sure oil is flowing
freelythrough thesupply line.
Clean the oil return line or return passages through the
brackets; these passages must be unrestricted so oil can
return to the engine.
Prelubricate compressor cylinder walls, piston rings, and
bearingswithcleanengineoilbeforeassemblingcompressor.
Always use a new mounting gasket and be sure oil hole in
gasket and compressor is properly aligned with oil supply
line.
Inspect pulley or gear and associated parts for wear or
damage.Theymust be aneatfiton compressorcrankshaft.
Replace pulley or gear if worn or damaged.
Installpulleyorgear on compressorcrankshaftmakingsure
it properly contacts the shaft and does not ride the key.
Tighten crankshaftnut to65-70 ft. lbs.andinstallcotter pin.
Besure theaircleaner isclean and properlyinstalled. Ifthe
compressor intake is connected to either the engine air
cleaner or supercharger, these connections must be tight
withno leakage.
Clean or replace any damaged or dirty air or water lines
which may be corroded, before connecting them to the
compressor. Use a new discharge fitting gasket.
Align compressor drive and adjust proper belt tension.
Tighten mounting boltssecurelyand evenly.
After installation run compressor and check for air, oil, or
water leaks at compressor connections. Also, check for
noisy operation.
DISASSEMBLY
GENERAL
Clean compressor exterior of road dirt and grease using a
good cleaning solvent. Before compressor is completely
disassembledthefollowingitemsshouldbemarked toshow
theirrelationship whenthe compressoris assembled:
The cylinder block in relation to crankcase, end covers’
relation to crankcase, position of crankshaft in relation to
crankcase, the cylinder head’s relation to the block.
Aconvenient methodto indicatethe aboverelationships is
to 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 cylinder head cap screws and tap the head
withasoft mallettobreak thegasketseal. Removetheinlet
valvespringsfromtheheadandinletvalvesfromtheirguides
in the block. Remove inlet valve guides from around the
inlet valve seats on the block taking care not to damage
seats. Scrape off any gasket material from the cylinder
head and block. Unscrew the discharge cap nuts from the
headandremovethe dischargevalvesandsprings.Inspect
the discharge valve seats for nicks, cracks, and excessive
wear and remove and replace if necessary.
FIGURE 11 - INLETADAPTER

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Thedischarge valvecapnuts shouldbe inspectedfor wear
and replaced if excessive peening has occurred. To
determineif excessivepeening has occurred,measure the
discharge valve travel. Discharge valve travel must not
exceed .046 inches (1.168 mm).
CRANKCASE BASE PLATE ORADAPTER
Remove the cap screws securing the base plate or base
adapter.Tapwithsoftmallettobreakthegasketseal.Scrape
offany gasketmaterialfromcrankcaseandplate or adapter.
CONNECTIONRODASSEMBLIES
NOTE: Before removing the connecting rods, mark each
connectingrod andits cap. Eachconnecting rodis
matched to its own cap for proper bearing fit, and
these parts must not be interchanged.
Straighten the prongs of the connecting rod bolt lock strap
and remove the bolts and bearing caps. Push the piston
withtheconnecting rodsattachedout the topofthe cylinder
block. Replace the bearing caps on their respective
connectingrods. Removethepiston ringsfromthe pistons.
If the pistons are to be removed from the connecting rods,
remove the wrist pin lock wires and press the wrist pins
fromthe pistonsand connectingrods. If thewrist pinshave
teflon plugs, remove plugs, then press out the wrist pins.
FIGURE 12 - TU-FLO®600AIR COMPRESSOR CYLINDER
HEAD
Ifthe pistonsare removedfrom therod, inspectthe bronze
wrist pin bushing. Press out and replace the bushing if it is
excessively worn. (See inspection of parts.) Discard the
pistonringsandtheconnecting rod journalbearings.Discard
thewrist pinbushings ifthey were removed (Fig. 13).
CRANKCASE(FIG. 14)
Removeend coverwith oilseal, removeend covergasket.
Replace oil seal after cleaning end cover.
Remove cap screws that hold opposite end cover to
crankcase; remove end cover and its gasket. Some
compressors have crankcases that have a shoulder for
positioning the crankshaft. In these cases, the crankshaft
mustbe removed throughone particular end.
Pressthe crankshaftand ballbearings fromthe crankcase
thenpressballbearings from crankshaft.Manycompressors
will have sleeve type bearings in the crankcase or in the
endcover. If the clearance betweencrankshaftjournal and
bearing exceeds .0065 in. (.165 mm) the sleeve bearing
shouldbe replaced withappropriate undersize.
BLOCK (FIG. 15)
If compressor is fitted with an air strainer, inlet elbow or
governor, removesame.
Remove cap screws securing cylinder block to crankcase;
separatecrankcaseandcylinderblockandscrapeoffgasket.
Removeunloaderspring,springsaddleandspringseatfrom
cylinder block (Fig. 15).
Removeunloader guidesand plungersand with the use of
shopairblowunloaderpistonsoutofcylinderblockunloader
pistonbores.
Removeinletvalveguides;inletvalveseatscanberemoved,
but only if they are worn or damaged and are being
replaced.Unloader borebushings shouldbe inspected but
notremoved unlesstheyare damaged.
PREVENTATIVE MAINTENANCE
Regularly scheduled maintenance is the single most
importantfactorinmaintainingtheairbrakechargingsystem.
RefertoTableAintheTroubleshootingsectionfora guide to
variousconsiderationsthatmustbegiventothemaintenance
of the compressor and other related charging system
components.
CLEANING AND INSPECTION OF PARTS
CLEANING
All parts should be cleaned thoroughly in mineral spirits
before inspection.

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FIGURE 13 - TU-FLO®600AIR COMPRESSOR CYLINDER BLOCKASSEMBLY
FIGURE 14 -TU-FLO®600AIR COMPRESSOR CRANK CASEASSEMBLY

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CYLINDERHEADASSEMBLY
Removeall carbondepositsfrom dischargecavitiesand all
rust and scale from cooling cavities of cylinder head body.
Scrape all foreign matter from body surfaces and use air
pressure to blow dirt particles from all cavities.
Discharge valves can be dressed by lapping them on a
piece of fine crocus cloth on a flat surface, provided they
arenot excessivelyworn.
CYLINDERBLOCK
Clean carbon and dirt from inlet and unloader passages.
Use air pressure to blow carbon and dirt deposits from
unloaderpassages.
Inlet valves, as in the case of discharge valves, not worn
excessively can be cleaned by lapping them on a piece of
fine crocus cloth on a flat surface.
LUBRICATION
Checkthe exterior ofthe compressor forthe presence ofoil
seepageandrefer totheTROUBLESHOOTING section for
appropriatetests andcorrective 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
Bendixair dryer.
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 whenusingthe BASIC
test are presented in APPENDIX A at the end of the
TROUBLESHOOTINGsection.
OILPASSAGE
Clean thoroughly all oil passages through crankshaft,
connecting rods, crankcase, end covers and base plate. If
necessary, inspect passages with a wire and blow foreign
matter out with air pressure.
INSPECTION OF PARTS
CYLINDER HEAD BODY
Inspect cylinder head body for cracks or damage.
WATER-COOLED TYPE
Use air pressure to test water jackets of cylinder head and
blockfor leakage. Replaceunit if leakageis found.
DISCHARGE VALVESAND SEATS
Ifdischargevalvesare wornandgroovedwheretheycontact
the seats, they should be replaced. If the discharge valve
seatsarewornexcessivelysothatthereisnolongerenough
metal left to reclaim them by lapping, the seats should be
replaced.
DISCHARGE VALVE SPRINGAND CAP NUTS
Replace all used discharge valve springs and cap nuts if
cap nuts cannot be reclaimed.
CRANKCASEAND ENDCOVERS
Check for cracks or broken lugs in crankcase and end
covers. Also, check oil passages to make sure they are
open and clean.
Ifan oilseal ringis usedin theend cover,check fitof ringin
ring groove. There should be .008 in. (.203 mm) to .015 in.
(.381mm)clearanceatthe gap whenplacedintheendbore
ofthe crankshaft.Ifthe oilring iswornthin orisdamaged, it
should be replaced. Inspect oil ring groove in end cover; if
groove is worn excessively, replace end cover or machine
groovefor nextoversize oil sealring. Ifthe crankshaftmain
bearingsare installed intheend cover,checkfor excessive
wear and flat spots; replace if necessary.
FIGURE 15 -TU-FLO®600AIR COMPRESSOR BLOCK ASSY

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CYLINDERBLOCK
Check for cracks or broken lugs on cylinder block. Also
checkunloaderbore bushingstobe suretheyare 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
inside the bushing, then inserting a 1/8 in. pipe threaded
rodand pulling the bushing straightup andout. Do not use
an easy-out for removing these bushings.
INLET VALVESAND SEATS
If inlet valves are grooved or worn where they contact the
seat, they should be replaced. If the inlet valve seats are
worn or damaged so they cannot be reclaimed by facing,
they should be replaced.
CYLINDER BORES
Cylinder bores which are scored or out of round by more
than.002 in.(.051 mm)or taperedmore than.003 in.(.076
mm)shouldbereboredor honed oversize.Oversizepistons
areavailablein.010 in.,.020in.,and.030 in.oversizes(Fig.
16).
Cylinder bores must be smooth, straight, and round.
Clearance between cast iron pistons and cylinder bores
should be between .002 in. (.051 mm) minimum and .004
in. (.102 mm) maximum (Fig. 16).
PISTONS
AnyofthreedifferentpistondesignsmaybefoundinTu-Flo®
600compressors asfollows: threering castiron, threering
aluminum or five ring cast iron. If either of the three ring
designsarefound,itisrecommendedthattheunitbeupdated
to the current five ring design. Piece numbers of five ring
piston, wrist pin maintenance kits and piston ring sets are
shown in Fig. 17.
Ifthecompressorhasfiveringpistonswhicharetobereused,
theyshould bechecked forscores, cracksor enlargedring
grooves;replacepistonsifanyoftheseconditionsarefound.
Measure each piston with a micrometer in relation to the
cylinderbore diameterto besure theclearance isbetween
.002 in. (.051 mm) minimum and .004 in. (.102 mm)
maximum.
Checkfit ofwristpins inpistons.Wrist pinclearance should
be from .0000 in. to .0006 in. (.015 mm). Check fit of wrist
pin in connecting rod bushing. This clearance should not
exceed .0007 in. (.018 mm). Replace wrist pin bushings if
excessiveclearance is found.Wrist pin bushingsshould be
reamedafter being pressedinto connectingrods. Replace
usedwrist pinlockwires. Compressorsmanufactured after
December, 1977, will have Teflon plugs in each end of the
wrist pins instead of the lockwire. The Teflon plugs (piece
number 292392) may be used instead of the lockwires on
all compressors (see Fig. 3).
PISTON RINGS
Check fit of piston rings in piston ring grooves. Check ring
gapwithrings installedincylinderbores. RefertoFig.18 for
correctgapand grooveclearance.
All rings must be located in their proper ring grooves as
shown.The ringscan beidentified bythe widthand should
beinstalledwith the bevelorthepip mark(ifany)toward the
top of the piston as shown.
FIGURE 16 - CHECKING CYLINDER BORE
FIGURE 17
5Ring Wrist Ring *Piston Pin
Size Piston Pin Set Maint. Kit
Standard 292529 292530 282525 289891
.010”
Oversize 292547 292530 282526 289892
.020”
Oversize 292548 292530 282527 289893
.030”
Oversize 292549 292530 282528 289894
* Includes 1 piston, 1 wrist pin, and 2 pin buttons.

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CRANKSHAFT
Check crankshaft screw threads, keyways, tapered ends
and all machined and ground surfaces for wear, scores, or
damage. Crankshaft journals which are out of round more
than .001 in. (.025 mm) must be reground. Bearing inserts
areavailable in.010 in.(.254 mm),.020 in.(.508 mm), and
.030 in. (.762 mm) undersizes for reground crankshafts.
Mainbearing journals mustbe maintained sobearings are
snug fit. The oil seal ring groove or grooves in crankshafts
fitted with oil seal rings must not be worn. The ring groove
walls must have a good finish and they must be square.
Check to be sure the oil passages are open and clean
throughthe crankshaft.
CONNECTING ROD BEARINGS
Check connecting rod bearings on crankshaft journals for
proper fit. Used bearing inserts should be replaced.
Connecting rod caps are not interchangeable. The locking
slots of the connecting rod and cap should be positioned
adjacentto eachother.
Clearance between the connecting rod journal and the
connectingrodbearingmust not belessthan.0003in.(.008
mm)or morethan .0021in. (.053mm) after rebuilding.
MAINBEARINGS
Check for wear or flat spots; if found, bearings should be
replaced. If type with sleeve bearing, this bearing should
bechecked forscores and wearand replacedif necessary.
UNLOADERMECHANISM
Usedunloadermechanism shouldbereplaced byunloader
kits (piece number 279615).
Thenewunloader pistonsshouldbe alooseslidingfit inthe
unloaderpiston bores ofthe cylinderblock.
REPAIRS
DISCHARGEVALVESAND SEATS
If discharge valve seats merely show signs of slight wear,
they can be dressed by using a lapping stone, grinding
compound and grinding tool. Install new valve springs and
re-dressedor newdischarge valves.
To test for leakage past the discharge valves, apply about
100 pounds of air pressure through the cylinder head
dischargeportand applysoapsuds atthedischargevalves
andseats.Leakagewhichwillpermittheformationofbubbles
is permissible.
Ifexcessiveleakageisfound,leavethe air pressureapplied,
andwith the useof afibreor hardwooddowel and hammer,
tap the discharge valves off their seats several times. This
willhelp thevalves toseat and shouldreduce anyleakage.
With the air pressure still applied at the discharge port of
thecylinder head,check forleakageat thedischarge valve
cap nuts. No leakage is permissible.
INLET VALVESAND SEATS
If inlet valve seats show sign of slight nicks or scratches,
they can be redressed with a fine piece of emery cloth or
by lapping with a lapping stone, grinding compound and
grinding tool. If the seats are excessively damaged to the
extent that they cannot be reclaimed, they should be
replaced. The dimension from the top of the cylinder block
totheinletvalve seatshouldnotexceed.113 in. (2.870mm)
not be less than .101 in. (2.565 mm).
Slightlyworn orscratched inletvalves canbe reclaimedby
lappingthemonapieceof fine crocusclothonaflatsurface,
butit issuggested that newinlet valvesbe installed.
ASSEMBLY
INSTALLINGCYLINDER BLOCK
Position cylinder block gasket and block on crankcase
according to markings made prior to disassembly. Using
cap screws with lockwashers, secure cylinder block to
crankcase at 220 to 250 inch pounds.
INSTALLINGCRANKSHAFT
If the crankshaft is fitted with oil seal rings, install rings.
Positionball bearingsand crankshaftin crankcasemaking
surethedrive endofthecrankshaft ispositionedasmarked
beforedisassembly.
If one end of the crankcase is counterbored for holding a
bearing, be sure the crankshaft is installed through the
correct end of the crankcase.
Carefully press crankshaft and bearings into crankcase
using arbor press.
FIGURE 18 - PISTONRINGPOSITIONSGAPS&GROOVE
CLEARANCE
TU-FLO®500 & 600 AIR COMPRESSOR
CORRECT GROOVE
CLEARANCE
NARROW
RING
WIDE RING
.0035”
.0015” .002”
.004”
CORRECT GAP
CLEARANCE WITH
RING IN CYLINDER
.0035
.015 WIDE
NARROW
WIDE
NARROW
INCHES MM
.038.0015
.051.002
.089.0035
.102.004
.381.015

12
Positiona rearend covergasket, whenused, overthe rear
endof the crankcase,making sure theoil holeinthe gasket
lines up with the oil hole in the crankcase. Position the end
cover oil seal ring, if used, in the groove in the end cover
boss. The end cover should be positioned correctly in
relationto theoil holesin thegasket and crankcase.As the
endcoverispositioned, theoilsealringmustbecompressed
as it is positioned in the crankshaft. Secure end cover to
crankcase with cap screws and lock washers.
If the opposite end cover requires an oil seal which was
removed on disassembly, a new seal should be pressed
intoendcover.Position newendcover gasket andcarefully
installendcover overcrankshaftand tocrankcaseavoiding
damage to the seal. Secure end cover with cap screw and
lock washers (220-250 inch pounds).
INSTALLING PISTONSAND 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
bushinglines upwith theone inthe rod.The newbushings
shouldthen bereamed orhoned toprovide between .0002
in. (.005 mm) and .0007 in. (.018 mm) clearance on the
wrist pin. Position connecting rod in piston and press in
wrist pin so that lockwire hole in the pin aligns with
that of the piston. Installnew lockwirethrough pistonand
wristpin and locksame by snappingshort end intolockwire
holeat the bottomof thepiston(Fig. 3).Teflon plugsin wrist
pin ends may be used instead of the lockwires (Fig. 3).
Installpiston ringsin correct locationwith ringpip marksup
(Fig. 18). Stagger the position of the ring gaps.
Prelubricate piston, piston rings, wrist pin, and connecting
rod bearings with clean engine oil before installing them in
thecompressor.
Remove connecting bolts and bearing cap from one
connecting rod. Turn crankshaft so one of its connecting
rodjournals isin the downward,center position.Compress
theringsintheir respective grooveswitharingcompression
tool.Insert the connectingrod with pistonthrough thetopof
thecylinder whosejournal isdown. Positionand attachthe
bearingcap totheconnecting rodmaking surethebolt lock
washers are properly positioned on the cap. Tighten
connecting rod bolts (105-120 inch pounds) and bend the
twonew lock washerprongs upagainstthe hexhead of the
bolt.Install theotherconnecting rodand pistoninthe same
manner.
UNLOADINGMECHANISM (FIG. 15)
The unloader pistons and their bores must be lubricated
with special lubricant piece number 239379 (dimethyl
polysiloxane) prior to installation. If new unloader kits are
beinginstalled, thepistons inthe kitare alreadylubricated.
Installtheunloaderpistonsin their bores withcautionagainst
cutting the o-rings or distorting the back-up rings.
Position unloader plungers in their guides and slip them in
and over the tops of the pistons.
Installtheunloader springseatin thecylinderblock;a small
hole is drilled in the block for this purpose. Position the
saddle between unloader piston guides so its forks are
centered on the guides. Install the unloader spring making
sure it seats over the spring seats both in the block and on
thesaddle.
Installinletvalveseatsiftheyhavebeenpreviouslyremoved.
Positionandinstall inletvalveguides, thendropinlet valves
in their guides. There should be a loose sliding fit between
guidesandvalves.
CYLINDERHEADASSEMBLY
Ifpreviously removed,the discharge valveseats shouldbe
installed. Drop discharge valves into their seats. Install
discharge valve spring and cap nuts.
Place the inlet valve springs in the cylinder head. Use a
small quantity of grease to hold them in place, just enough
grease to keep the springs from falling out. Place cylinder
headgasketon cylinderblock.Carefullyalign cylinderhead
assembly on block and install cap screws. Torque to
175-225 inch pounds.
AIRSTRAINER
If the compressor has its own air strainer, reassemble with
new or cleaned element. Assemble to block with a new
strainergasket.
GOVERNOR
If compressor is type with pad mounted governor, install a
properlyfunctioninggovernor using anewgovernorgasket.
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.
Fitthe endof all crankshaftswith keys,nuts andcotter pins
as required and then protect the ends against damage by
wrapping with masking or friction tape.
Theopen bottomof enginelubricated compressorsshould
beprotected againstthe entranceof dirtduring handlingor
storage,by installinga temporarycoverover base.
TESTINGREBUILTCOMPRESSOR
In order to properly test a compressor under operating
conditions, a test rack for correct mounting, cooling,
lubricating and driving the compressor is necessary. Such
testsarenotcompulsory iftheunithasbeen carefully rebuilt
byan experiencedperson.

13
Acompressorefficiency orbuild-uptest canberun whichis
not too difficult.An engine lubricated compressor must be
connectedtoanoilsupply line ofatleast15poundspressure
during the test and an oil return line must be installed to
keepthecrankcasedrained.The compressor(whentested)
should be tested without a strainer.
Tothe dischargeportofthe compressor connectareservoir
or reservoirs whose volume plus the volume of the
connecting line equals 1300 cubic inches. Run the
compressor between 1700 and 1750 RPM. Elapsed time
that the compressor takes to build up from 0 to 100 psi
shouldbe36 secondsmaximum.Duringthe abovetest,the
compressor should be checked for oil leakage and noisy
operation. TABULATED DATA
NumberCylinders 2
Bore Size 2.75in.
6.985cm
Stroke 1-11/16in.
4.287cm
Piston Displacement at 14.5cfm
1250RPM 410.6liter/min
PistonDisplacementper 20.0 cu. in.
Revolutionat1250RPM 327.74 cc
MaximumRecommendedSpeed(RPM) 2400
MinimumCooling WaterFlow for 2.5 gal/min
Water-Cooledcompressorsat 9.46liter/min
MaximumSpeed
HorsepowerRequiredat1250RPM 3.2
Against 100 psi
MinimumOilPressureRequired 5 psi
atEngineIdlingSpeed
MinimumOilPressureRequired 15 psi
atMaximumEngineGovernedSpeed
COMPRESSOR TROUBLESHOOTING
IMPORTANT: The troubleshooting containedin thissection
considers the compressor as an integrated component of
theoverall airbrake chargingsystem andassumes thatan
airdryer isinuse. Thetroubleshooting presentedwillcover
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.
FIGURE19- SPONGE TYPEAIR STRAINER EXPLODED VIEW

14
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. Forvehicles with Antilock Traction Control(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.

*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) . . . . . . . . . . . . . . . . . 23 - 24
Doesn’t build air (10.0) . . . . . . . . . . . . . . . 25
Air dryer:
Doesn’t purge (14.0) . . . . . . . . . . . . . . . . . 26
Safety valve releases air (12.0). . . . . . . . . 26
Compressor:
Constantly cycles (15.0) . . . . . . . . . . . . . . 26
Leaks air (16.0) . . . . . . . . . . . . . . . . . . . . . 27
Safety valve releases air (11.0). . . . . . . . . 25
Noisy (18.0) . . . . . . . . . . . . . . . . . . . . . . . . 27
Reservoir:
Safety valve releases air (13.0). . . . . . . . . 26
INDEX
Air Coolant
Engine
Oil
Compressor leaks coolant (17.0) . . . . . . . . . . 27
Oil consumption (6.0) . . . . . . . . . . . . . . . . . . . 23
Oil Test Card results (1.0) . . . . . . . . . . . . . . . . 18
Oil is present:
On the outside of the compressor (2.0). . . 19
At the air dryer purge/exhaust
or surrounding area (3.0) . . . . . . . . . . . 19
In the supply reservoir (4.0). . . . . . . . 20 - 22
At the valves (5.0) . . . . . . . . . . . . . . . . . . . 22
At air dryer cartridge (7.0) . . . . . . . . . . . . . 23
In the ping tank or compressor
discharge aftercooler (8.0) . . . . . . . . . . 23
Symptom Page Number
(1) Oil Leakage at Head Gasket . . .28
(2) System Leakage . . . . . . . . . . . .28
(3) Compressor Discharge and
Air Dryer Inlet Temperature . . . .28
(4) Governor Malfunction . . . . . . . .29
(5) Governor Control Line . . . . . . . .29
(6) Compressor Unloader . . . . . . . .29
BASIC Test Information . . . . . . 30-32
Test Procedures
Maintenance Schedule and
Usage Guidelines (Table A) . . 17
Symptom Page Number
Maintenance & Usage Guidelines
15

16
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
aircompressor istypically cooled bythe enginecoolant
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
pressurelevel bymonitoringthe pressurein theservice
(or“supply”) reservoir. When the airpressure 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
airpressure dropsto the“cut-in”setting ofthe governor,
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.
Aircompressors aredesignedto 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 17) 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.
Whenthetemperatureofthecompressedairthatenters
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
dryerandintothe airsystem. Largerdiameterdischarge
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 33-35). 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
purgedwhen thegovernor reachesits“cut-out” setting.
Forvehicles withaccessoriesthat aresensitiveto small
amounts of oil, we recommended installation of a
Bendix®PuraGuard®system filter,designed to minimize
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.

17
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 dryer inlet, (and resultant oil-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-vaporcondensesandcanberemovedbythe air dryer. Dischargeline upgrades arenot
coveredunder warranty. Note:Tohelp prevent discharge linefreeze-ups,shorterdischarge
linelengths orinsulationmayberequired in coldclimates. (SeeBendix BulletinsTCH-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 in cases
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

18
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
BendixAirSystem InspectionCup(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 30 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 engineshouldbe shutoffandthe ignition
keyshould beremoved. Wherecircumstancesrequire that
the engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from contact
withmoving,rotating,leaking,heatedorelectrically charged
components.
3. Donot attempt toinstall,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. Never removea componentor plug
unless you are certain all system pressure has been
depleted.
8. Useonly genuine Bendix®replacementparts,components
andkits.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 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 morewheels on a drive axle are liftedofftheground
and moving.

Symptom: What it may indicate: What you should do:
19
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 28.
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)

20
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
Aonpage 17, Column4 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 17,
someoil in thereservoirs isnormal.
ðDrainall airtanksand checkvehicle atnext
service interval using the Bendix®BASIC
test. See Table A on page 17, column 3
and4, for recommended service schedule.
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 28), 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 17, column
3 for recommended air dryer cartridge
replacement schedule.
Maintenance
(a)
ðGo to Test 2 on page 28.
ðSee Table A, column 1, on page 17 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:The costsincurred (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 17,
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)Compressor maybeundersized for
the application.