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8/6/2019 Brake Kit Troubleshooting Guide
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8/6/2019 Brake Kit Troubleshooting Guide
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8/6/2019 Brake Kit Troubleshooting Guide
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Table of Contents
Brake Bleed Guide
BenchBleedingandTestingtheMasterCylinder...............................................Page4
BleedingtheLines..............................................................................................Page6
Brake Troubleshooting
TroubleshootingChart.........................................................................................Page7
TroubleshootingBleedingDifculties.................................................................Page10
TheRightValves.................................................................................................Page10
CheckBoosterPushrodAdjustment...................................................................Page11
CheckFlexibleBrakeHoses...............................................................................Page12
CheckPedalAssembly.......................................................................................Page12
CheckProperAlignment.....................................................................................Page13
MasterCylinderTest...........................................................................................Page13
PowerBrakeBoosterTest..................................................................................Page14
CombinationPropValveTest..............................................................................Page15
StickingProportioningValve...............................................................................Page15
BrakeFade.........................................................................................................Page16
Typical Brake System Congurations
QuickReferenceGuides.....................................................................................Page16
Copyright2006byMBMarketing&Manufacturing,Inc.
No reproduction, digital or otherwise
canbemadeofanypartofthiscatalog
withoutexpresswrittenauthorization.
CautionWeencourageyoutounderstandthattheinstallationofanycomponentor
kitshouldonlybeperformedbyapersonthatisexperiencedintheproper
operationofbrakesystems.Further,theresponsibilityfordeterminingthe
suitabilityofacomponentorkitisyourresponsibility.
Be SafeWestronglyencourageyoutotestyourbrakesunderacontrolledcondition,
beforeoperatingthevehicle.Severalstopsinasafeareaatlowspeeds
shouldbemadeandthengraduallyworkuptonormalspeeds.Obviously,
nooneshoulddrivewithanuntestedbrakesystem.
8/6/2019 Brake Kit Troubleshooting Guide
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Brake Bleed Guide
Read these instructions carefully and completely before installing your Disc Brake Kit. This
guide is set up to be generally followed in order. Here are a few basics to help ensure a safe
brake system:
Followingthestepsinthisguidewillensurethatyouwilleasilypinpointanytroublespotsinyour
brakesystemwhileinstallingandassemblingthesystem,eliminatingmanyheadaches.FollowittotheT,andwearecertainyouwillhaveapleasurableexperiencewithyourupgrade.
Useonlynewbrakeuid.Contaminateduidcancausedamagetothesensitivehydraulicbrake
componentsduringthebleedingprocess,corrodecomponentsandincreasethelikelihoodof
systemfailure.Evenunuseduidthatwasopenedatanearliertimeshouldnotbeused.Brakeuid
ishydroscopicmeaningthatitabsorbsmoisturefromtheair.Thismoisturedegradestheproperties
ofthebrakeuid.
Cleanlinessisveryimportant.Makesureyoucleanthettingsandsurroundingareabefore
openinganypartofthebrakesystemtokeepcontaminantsfromenteringtheuid.
Forpowerbrakeupgrades,besuretocheckforaminimumof18in.ofvacuumpriortoperforming
theupgrade.Vehicleswithtallheadsorsuperchargersmostlikelywillnothavesufcientvacuum.If
youdonothavesufcientvacuum,checkyourintakemanifoldforclogging,vacuumttingsandfor
collapsedvacuumlines.Alsoaskusaboutour12voltvacuumpump.
Nevereliminateloopsfromvacuumlinesastheseactasmoistureandvaportraps.Checkthe
vacuumlinesforgasodororthepresenceofmoisture.Gasfumescandeterioratetheinternal
rubbercomponentsofthebooster.
Donotusepetroleum-basedsolventstocleanbrakecomponents.Useonlycleaninguids
specicallydesignedforbrakessincetheyleavenoresiduewhentheydry.
Donotusecompressedairtodrybrakecomponents,evenlteredairmaycontainmoistureor
tracesofoil.
Checkbrakelinesforcracked,leakingorswollenlines.Thesemustbereplaced.
Donotmoveordrivethevehicleuntilarmpedalisestablished.
Bench Bleeding and Testing the Master Cylinder
ManypeopleskipthisVITALLYimportantstepinbleedingtheirbrakesystem.Benchbleedingthe
mastercylinderMUSTbeperformedanytimeamastercylinderisinstalled.Ifthemastercylinderisnotbled,itwilltakeyouatleasttwiceaslongtobleedthesystemandthenthereisnoguaranteethatyou
haveremovedalltheairfromthesystem.Themastercylindertestisapreliminaryprecautionandmay
needtobeperformedatalatertimeshouldtherebeaneedforfurthertroubleshooting.
DO NOT SKIP THIS STEP!Failure to follow these procedures is unsafe and may void your warranty!1. AllnewmastercylindersfromMBMincludeabenchbleedingkitthatincludeseverythingyouneed
toperformthebenchbleedingprocess.
5
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2. Beforebenchbleedingthemaster,completelyinstallallofyourbrakecomponentsandupgrades
includingthemastercylinderandbrakelines.Thisissothatyoucanhookupthemastercylinder
assoonaspossibleafterithasbeenbenchbledtokeepgravityfromleechinguidfromitduring
theinstallationoftheothercomponents.
3. Afterinstallingthesystem,removethemastercylindercompletelyfromthevehicle.Master
cylindersMUSTbebenchbledoutsidethevehicleandwithoutanyothercomponentsattached.
Thismeansthatifthekitisshippedwithabooster,proportioningvalveandplumblinesattachedtothemastercylinder,theymustallberemovedpriortobenchbleeding.
4. Besuretoplacethemastercylinderlevelinavicetosecureitproperly.Ifthemastercylinder
isnotlevel,notalltheairwillbeabletoberemovedfromthemastercylinder.Thisisoneofthe
mainreasonswebenchbleedthemastercylinderoffofthevehicle,togetitperfectlylevelduring
thebleedingprocess.Removethemastercylindertopandllitwithbrandnewbrakeuidtothe
appropriatelevelasindicatedinthemastercylinder.Thisisgenerallyabout1/2-1fromthetopof
thereservoirliptoallowforthermalexpansionofthebrakeuid.
5. Inserttheplasticttingsthattintothetwosideportsofthemastercylinder,(Note:ondualported
mastercylinderswheretherearefourports,chooseonesideandusebothportsonthatoneside
toperformthebleedprocess.)Insertonerubbertubeintoeachoftheplasticttingsandthelooseendsshouldbeinsertedintothemastercylinderreservoir.Theplastictabshouldbeusedtohold
thetubesinplacebyslippingitoverthereservoirseparatorandthehosesthroughtheroundholes.
6. Coverthetopofthemastercylinderwitharagtohelppreventuidfromsplattering,protecting
yourpersonaswellasyourvehicle.Beawarethatbrakeuidismildlycorrosiveandmaydamage
paintedsurfaces.
7. Usingawoodendowelorabluntmetalrod,compressthemastercylinderplungerwithslowdeep
strokes.
8. Oncethelargebubbleshavesubsideditshouldbecomeincreasinglymoredifculttocompressthemastercylinderpiston.Continuetodosowithslowshortstrokesatthebottomofthepistonstroke
untilnomorebubblesappear.
9. Therubberhosesandplasticttingsmaynowberemovedfromthemastercylinder.
10.Securethemastercylindertop.
11.Nowtestthemastercylinderbyblockingoffthemastercylinderportsusingthecorrectsize
invertedareplugsorboltswiththeappropriatethreadsizefortheportsonyourmastercylinder.
Dualportmastercylindersthathaveportsonbothsidesneedtohaveallfourportsplugged.The
protrudingconeoftheinvertedareseatinthemastercylinderportismadeofasoftmaterialthat
caneasilybedeformedifovertightened.Ifusingbolts,besuretojustsnugtheboltssoasnottodamagetheconesealsurface.Thisconemateswiththeinvertedare(expandedmouthopening)
ofthebrakelines.Ifyouhavetheability,youcanalsodrillapointintotheendofthebolttohelp
preventthisfromoccurring.
12.Attempttocompressthemastercylinderpistonforapproximately30seconds.Themastershould
giveasolidandunchangingresistancetotheconstantforce.
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13.Installthemastercylinderandleaveenoughroomonthemountingnutstoallowforsome
movementofthemaster.Thiswillallowyousomebreathingroomwhilescrewinginthehydraulic
linestohelppreventcross-threadingthettings.
Bleeding the Lines
Manyofyouwillbetemptedtoglazeoverthissectionthinkingthatyoualreadyknowthis.Continue
readinganyway,justbearwithus.Youmaypreventsmalloversightsthatwillcausemajorheadaches.Wehavedevisedthistoassistyouintheinstallationofyourkitandtoreducethenumberoftechnical
callsinregardstotheseissues.Manytimeswegetcallsfrompeoplewhoshouldhaveknownbetter.
Soletsworktogethertomakesureyourinstallationwillbeassmoothaspossible.
1. Formastercylinderupgradestoexistingpowerboostersetups,removeanyresidualvacuuminthe
boosterbyapplyingthebrakepedalafewtimeswiththeengineoff.
2. Removethemastercylindercoverandchecktheuidlevel.Makesureitisattheappropriatelevel
foryourmastercylinder,thisistypically1/2to1fromthelip.Besuretochecktheuidleveloften
duringthebleedingprocessandadduidasnecessarytopreventairfromenteringthemaster
cylinder.IfthishappensyouMUSTstartoveratbenchbleedingthemaster!
3. Replacethemastercylindercap.
4. Theuseofourspeedbleederswillallowyoutoperformthisjobbyyourselfbysimplycracking
thespeedbleederenoughtoallowuidtobeforcedthrough.Thespeedbleederhasaninternal
checkvalvethatpreventsuidandairfromreturningintothecaliperoncethepedalisreleased.
Thisremovesthenecessityofclosingthebleederscrewbeforethepedalisreleased,allowingone
persontobleedthebrakes.Otherwiseyouwillneedanassistanttopumpthebrakepedalwhile
youopenandclosethebleederscrewsattheappropriatetimesduringthisprocess.
5. Thewheelfarthestawayfromthemastercylinderisbledrstwhichinmostcasesisinthisorder:
rightrear,leftrear,rightfront,leftfront.Failuretobleedintheproperorderwillcauseairtoremaininthelines.Thisisbecauseifyoubleedashortline,(ex.frontlines)beforebleedingalongline(ex.
rearlines),theuidintheshortlinewillcompressandpreventenoughpressurefrombeingbuiltup
inthelonglinetoexpeltheair.Furthermore,incorrectbleedingorderwillcausepressuretobuild
upononesideoftheproportioningvalve,causingittocloseonthelowpressuresidemakingit
impossibletoforceuidtotherearlines.Ifthishappensyouwillneverbeabletobleedthesystem
untilyoureadjusttheproportioningvalveasdescribedlaterundertheheadingTestCombination/
ProportioningValveandthenstartover.
6. Itmaybenecessarytoremovethe
calipersfromthecaliperbrackets
whileleavingthehosesattached.The
calipersmustbeorientedinsuchawayastoensurethebleederscrews
pointup.(Seegureatright)Ifyou
bleedthelineswiththecalipersonthe
rotor,airmaybecometrappedinside
thecaliperreservoirandthebleeding
willbeunsuccessful.Thecaliper
shouldbeorientedinsuchawayas
toallowairinsidethecaliperinternal
reservoirtoescape.Sometimesthis
Allairwillbebled
fromthiscaliper
AllairwillNOTbebledfrom
thiscaliperasairgetstrapped
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meansthebleederscrewispointingstraightupandsometimesitisatalittlebitofanangle.Itis
recommendedthatyoudonotallowthecalipertohangfromthebrakehose.Insteaduseapiece
ofwireorhangertopositionthecaliperscorrectly.Otherwisedamagetothebrakehosesmay
result.Ifyoudonditnecessarytoremovethecaliperfromtherotor,becertaintoinsertablock
thatisapproximatelythesamethicknessastherotorbetweenthebrakepadstopreventthecaliper
pistonsfrombeingpushedoutofthecaliper.
7. Crackthebleederscrewsattheappropriatewheeljustenoughtomakeiteasytoloosenlater.Attachalengthof3/16clearplastic,vinyltubetotheendofthebleederscrew.Submergethe
otherendofthetubeintoacontainerlledwithbrakeuid.
8. Crackthebleederscrewopenjustenoughtoallowuidtoleavethevalveandhaveanassistant
slowlyandrmlyapplypressuretothepedal.Havetheassistantholdthepressureonthepedal
untilyouseenomoreairbubblescomingoutofthehose.Closethebleederscrew.Thenhavethe
assistantreleasethebrakepedal.
9. Repeatstep8untilnomoreairisseenleavingthetube.
10.Closethebleederscrewtotheappropriatetorqueforyourapplicationandproceedtothenext
wheelinthebleedingorder,repeatingsteps8and9foreach.Besuretochecktheuidlevelinthemastercylinderfrequently.
11.Rellthemastercylindertotheappropriatelevelwhennishedwiththeentirebleedingprocess.
12.Checkthepedal,itshouldfeelsolidwhendepressedwithnosponginessandshouldholdunder
constantpressurewithoutdropping.Ifnecessary,repeattheentireprocess.
13.IfyouareindoubtoftheeffectivenessofthebrakesystemDONOTDRIVETHEVEHICLE!
Brake Troubleshooting
Troubleshooting Chart
Symptom Cause Solution
NotEnoughBrake BrakeFade SeeBrakeFadeonpage16
Vehicleistooheavyfor
brakesystem(drumbrakes,
addedlargerengine,etc.)
Performboostertest,seepage14
Performmastercylindertest,seepage13
Installboosterorincreaseboostersize
Increaserotorsize
BrakeLightonDashison Airinlines BleedBrakeSystem
UseSpeedBleederstofacilitatebleeding
Underbraking-Carpullstoonesideoronewheel
locksup
OiloruidonbrakepadDebrisinbrakelines
Collapsedlines
Cleanorreplacepadsandcheckfordirty,damagedorleakylinesorcalipers
RockHardPedal InsufcientVacuum Checkvacuumpressure,seePowerBrake
BoosterTestonpage14
BlockedVacuumCheck
Valve
Badpowerbooster
FrozenWheelCylinder
BindingPedallinkage
CrackedVacuumHose
SeePowerBrakeBoosterTestonpage14
Replacecaliper
Inspectpedalassembly
Inspectvacuumhosetoboosterforcracks
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Spongy,LoworNoPedal AirinLines Bleedbrakesystem
UseSpeedBleederstofacilitatebleeding
AeratedBrakeFluid Completelyushandreplacebrakeuid
Checkforoverheatingconditions
Parkingbrakeoutof
adjustment
Checkcablesettingindrums/rearbrakes
Unequalpressurebetweenfrontandrearlines SeeCombination/ProportioningValveTestonpage15
Incorrectpedalratio SeeCheckPedalAssemblyonpage12
Badexiblebrakehoses SeeCheckFlexibleBrakeHosesonpage
12
Boosterpushrodoutof
adjustment
Checkboosterinstallationprocedures
Calipermisalignedtorotor
becauseofbentcaliper
bracketorloosewheel
bearings
Checkcaliperbracketalignment
Replacewheelbearings
Hardlinesbentabovemastercylinderuidlevel
Replumbhardlinetoremainbelowmastercylinderuidleveltoavoidtrappingairin
thelines
Mastercylinderboresize
toosmallforapplication
Smallboremastercylinderrequireslonger
pedaltraveltoapplybrakes
Badpowerbooster SeePowerBrakeBoosterTestonpage14
Airinmastercylinder Benchbleedingthemastercylinder,see
page4
Badmastercylinder SeeMasterCylinderTestonpage13
BadorleakyCaliper Replacecaliper
Mastercylinderlocated
belowcalipersorlinesw/
noresidualcheckvalve
SeeTheRightValvesonpages10
DrumBrakes:Noresidual
checkvalves
SeeTheRightValvesonpages10
DrumBrakes:Upgraded
largerdrums
Installboosterorincreaseboostersize
DrumBrakes:Overarched
shoes
Replacedrum,itmayhavebeenturnedtoo
manytimescausingnotenoughcontact
betweenshoesanddrum
DrumBrakes:Oversized
WheelCylinderformastercylinder
Replacewithlargerboremastercylinder
8/6/2019 Brake Kit Troubleshooting Guide
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OverheatingorDragging
Brakes
Improperlyadjustedparking
brake
Checkmanufacturersrecommended
settings
Pre-loadedmastercylinder
orpowerbooster
SeeCheckPedalAssemblyonpage12
Badpowerbooster SeePowerBrakeBoosterTestonpage14
DrumBrakes:Residual
checkvalves
Removeresidualcheckvalve
Frozenparkingbrakecable Replaceparkingbrakecable
BadCalipersorwheel
cylinders
Replacecaliperorcylinder
Overlledmastercylinder Filltocorrectlevelformastercylinder,
typically1fromlip
DrumBrakes:Drumsoutof
adjustment
Drumsmaybeadjustedtootight,readjust
Pedaltoolowor
excessivepedalfreeplay
Incorrectpedalratio
Toomuchspacebetween
boosterpushrodand
mastercylinderpushrod
SeeCheckPedalAssemblyonpage12
ParkingBrakenotworking ParkingBrakeoutof
adjustment
Checkmanufacturersrecommended
settings
PoorPanicBraking Airinlines Bleedbrakesystem
UseSpeedBleederstofacilitatebleeding
BrakeFade SeeBrakeFadeonpage16
Vehicletooheavyforbrake
system(drumbrakes,
addedlargerengine,etc.)
Testbooster,seepage14
Testmastercylinder,seepage4
Installboosterorincreaseboostersize
Increaserotorsize
InsufcientVacuum Checkvacuumpressure,seePowerBrake
BoosterTestonpage14
BlockedVacuumCheck
Valve
SeePowerBrakeBoosterTestonpage14
Badpowerbooster SeePowerBrakeBoosterTestonpage14
DrumBrakes:Upgraded
largerdrums
Installboosterorincreaseboostersize
DrumBrakes:Noresidual
checkvalves
SeeTheRightValvesonpages10
DrumBrakes:Overarched
shoescausingnotenough
contactbetweenshoesand
drum
Replacedrum,itmayhavebeenturnedtoo
manytimes
DrumBrakes:Oversized
WheelCylinderformaster
cylinder
Replacewithlargerboremastercylinder
8/6/2019 Brake Kit Troubleshooting Guide
10/2011
Troubleshooting Bleeding Difculties
Ifyouarehavingdifcultygettingalltheairoutofthesystemoryouarenotobtainingarmpedal,try
thesestepstoassistinthebleedingprocessandtrackdownproblemareasonthevehicle.Aspongy
pedalisusuallycausedbyairinthesystem.
1. Whilebleeding,raisetheendofthevehiclethatisbeingbled,thismayhelpairtrappedinthesystem
torisetowardsthebleederscrew.
2. Whilebleeding,lightlytapthecaliperwithahammer.Thiscandislodgeairbubblesthatclingtothe
wallsofthecaliperreservoir.
3. Checkfordamagedbrakehosesthatmaybeinternallyexpandingfromthelinepressure.(See
CheckFlexibleBrakeHoses onpage12).
4. Uselinelocks(vice-grips)torestrictuidowintherubberlinesateachwheelbetweentheframe
andtheaxletohelppinpointthetroublespot.Lockallfourwheelsatthesametime.Beawarethat
crushingthebrakelinescandamagethem.Tohelppreventthis,wrapthejawsofthelinelocks
withashoptowelandclosethelinelocksjustenoughtorestricttheowofuid.DONOTOVER
TIGHTEN!
5. Withthelinestoallfourwheelsblockedoff,checkthepedal.Youarelookingforarmhardpedal
thatdoesnotdropunderconstantpressureoverashortperiodoftime.Ifyougetahardpedal,then
theproblemisdenitelyatoneofthewheels.Ifthepedalisstillspongy,rstmakesurethelinesare
effectivelyrestrictedandtrythepedalagain.Ifyoustilldonothavearmpedal,thenremovethe
mastercylindertofollowthebenchbleedandtestprocedure.
6. Ifyoudohaveahardpedal,thenremovethelinelocksfromthefarthestwheelfromthemaster
cylinderandpressthepedal.Ifthepedalisspongyagain,thewheelyoujustreleasedistheproblem
wheelandrequiresfurtherbleeding.(Inreardiscbrakes,theproblemmayalsobethattheparking
brakeneedsadjustment.Checkyourparkingbrakeadjustmentbeforeproceeding.)Makesurethatallthestepsforbleedingarefollowed.Ifyouarestillhavingdifculty,wesuggesttheuseofspeed
bleederstohelpensureairdoesnotreturninthelineswhenthepedalisreleased.Otherwisea
powerbleedingsystemmayneedtobeemployedoraprofessionalbrakespecialistmayneedto
checkthesystem.
7. Ifthepedalisstillrmthencontinueontothenextwheelintheproperbleedingorder,whichisthe
wheelwiththenextlongestlineinthesystem,releasethelinelockatthatwheelandtestthepedal
again.Notethatitisnormaltohaveasmallamountofincreaseintravelasyoureleasethelinelocks
fromeachbrakehose.
The Right Valves
Usingthecorrectvalvingforyourapplicationiscriticaltotheproperoperationofyourbrakesystem.
Therearefourtypesofvalvesthatperformdifferentfunctionstothebrakesystem.
Metering Valves-ThesevalvesareusedtoequalizebrakingactionofaDisc/Drumbrakesystem
bypreventingthediscbrakesfromapplyinguntilabout75-135psihasbuiltupinthe
lines.Thisdelaysthediscbrakesandallowsthedrumstocatchup.Thisprovides
rearstabilityonwetsurfacesandreducesfrontpadwear.Meteringvalvesare
generallylocatedinthelinestothediscbrakes.Inmostofourkits,themetering
valveisapartofthecombination/propvalve.
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Proportioning Valves-Thefunctionoftheproportioningvalveistolimitpressuretotherear
brakesrelativetopedalforce,especiallywhenhighpressureisrequiredtoapplythefrontdisc.This
preventstherearwheelsfromlockingupasweightisshiftedforwardduringbraking.Proportioning
Valvesaregenerallylocatedinthebrakelinetotherearbrakesandsometimes
areincorporatedintothemastercylinder.Theyareavailableaseither
presetoradjustablevalves. Note that adjustable proportioning valves
are not DOT approved for street driving and should only be used for
racing applications!
Residual Check Valves-Thesevalvesareusedtoholdacertainamountofpressureinthelines
evenwhenthepedalisnotpressed.Thisisasortofpreloadedlinepressuretoactivatethe
brakesmorequickly.Theywillgiveahigher,harderandmoreresponsivepedal.Residual
checkvalvesshouldnotbeusedasasubstituteforaproperlyfunctioningsystem.
Forinstance,donotuseresidualcheckvalvesinplaceofcompleteandproper
bleedingproceduresaspresentedinthisguideandourBrakeBleedingGuide.
Checkvalveswillmostlikelybenecessarywhenthemastercylinderislower
thanthecalipersorhardlinesrunhigherthanthemastercylinderuidlevel.
Indiscbrakesa2lb.residualcheckvalvepreventsuidfromowingback
withoutcausingthebrakestodrag.Withdrumbrakes,a10lb.valveisusedto
compensateforreturnspringtensioninthedrums.Residualcheckvalvesaregenerallycolorcodedbluefor2lb.andredfor10lb.foreasyidentication.
Combination Valves-Thesevalvesoffermultiplefunctionalityinasingleunit.Theycombinethe
functionsofbothameteringvalveandaproportioningvalvewiththeaddition
ofabrakelightwarningswitch.Thebrakelightwarningswitchsignalswhen
thereisanimbalanceofpressureinthesystemcausedbyaprobleminthe
frontorrearbrakes.Theyarebyfarthebestvalvetouseforalldiscbrake
conversions.AllourkitsuseDOTapprovedCombinationValvesdesigned
specicallyforeitherDisc/DiscorDisc/Drumapplications.
Check Booster Pushrod Adjustment
Thepushrodthatactuatesthemastercylindermustbeproperlyadjusted.Ideallythereshouldbe
onlyslightclearancebetweentheboosterpushrodandthemastercylinderpushrod.Interferencewill
preloadthemastercylinder.Whenthesystemispreloaded,itbuildspressureeachtimethepedalis
pressed.Sincethemastercylinderisnotallowedtofullyreleasethepressurefromthepreviousstroke,
thesystemwilleventuallylockthewheels.Toomuchclearancewillcauseexcessivefreeplayinthe
pedal.
TherearebasicallytwodifferentmastercylindersthatweuseforourChevyandFordkits,thedeep
boremastercylinderandtheshallowboremastercylinder.Todetermine
whichmastercylinderyourboosterissetuptomatewith,youcandothefollowingsimplecheck.Forshallowboremastercylinders,thepushrod
shouldbeapproximatelyushwithorbelowtheboosterface.Deepbore
mastercylinderswillprotrudepastthefaceoftheboosterbodybyabout
1to1-1/2.Notethatdeepboremastercylindersarerequiredformanual
brakesandshallowboremastercylindersaregenerallyusedforpower
brakesystems.Wenowsupplyamastercylinderpistonadapter(pictured)to
accommodatebothmastercylinders.Youwillonlyusethisadapterwhenyou
haveadeepboremastercylinderwithashortboosterpushrod.
Pistonadapter
8/6/2019 Brake Kit Troubleshooting Guide
12/2013
Check Flexible Brake Hoses
Inspecttheexiblebrakehosesfortypicalsignsoffatigue.Hosesshouldbecheckedfor:
Damage:Checkforlargesurfacecracks,scufngorwornspots.Iftheoutercasinghassevere
cracksorabrasions,thehoseneedtobereplaced.Thecasingistheprotectionforthehose,ifitis
damaged,thedeteriorationofthehosecantakeplacewithpossibleburstfailure.Linesshouldbe
exibleandrmratherthanhardandstiff.
FaultyInstallation:Twistingthehoseorrubbingagainstwheels,tiresorchassiswillcause
prematurelinedeterioration.
Makesurethatthetubeandhosematingsurfacesarecleanandfreefromnicksandburrs.Newseal
washer(s)shouldbeused.Doublewallsteeltubingshouldalwaysbeusedtoreplacehardlines.Care
shouldbetakenwhenreplacingbraketubing,tousetheproperbendingandaringtoolsandtoavoid
kinking,routingthetubesagainstsharpedges,movingcomponents,inhotareasorabovethemaster
cylinderuidlevel.Alltubesshouldbeproperlyattachedwithappropriateretainingclipsandtabs.
Check Pedal Assembly
Somethingthatmanypeoplearenotawareofwhenupgradingtheirsystemisthebrakepedal
adjustment.Improperpedaladjustmentcandothefollowing:
Preloadtheboostercausingbrakestodragandeventuallylockup.
Damagetheboostersinternalcomponentsbyactuatingatanimproperangle.
Allowslopinthepedalifadjustedtoolow.
Manyvehicleshaveasecondholeonthepedalassemblythatwasoriginallyintendedforpowerbrake
applications.Therequiredholeisgenerally1to1-1/2lowerthantheoriginalmanualbrakehole.Ifthereisnosecondhole,youmayneedtodrilltheholeinthepedalarmtoproperlyalignthepushrod.
Theeasiestwaytodeterminetheperfectlocationforthisholeistondthecenterofthepushrods
verticaltraveltoensurethatitsactuationisasinlinewiththeboosteraspossible.
1. Gentlylifttheendofthepushroduntilitstopsandnotethelocationwheretheclevisonthepushrod
locatesonthepedalarm.Markthislocation.
2. Thengentlypushthepushroddownuntilitstops.Markthislocationaswell.
3. Theproper hole locationisinthemiddlebetweenthetwomarksonthepedalarm.Markanddrill
thenewholeinthecenterofthepedalarm.Attachthepushrodtothepedalarm.
4. Checkfreeplayinthepedalbyapplyingpressuretothepedalwithyourhandandnotinghowfar
thepedaltravelsbeforeresistanceisfelt.Itshouldbeapproximately1/4.Thisfreeplayallowsthe
mastercylinderpistontoreturntotheat-restpositionandpreventspreloadingthesystem.Too
muchfreeplaywilldropthepedaltoofarbeforeapplyingbrakepressureandmayevenhitthe
oorbeforeapplyingfullbrakingforcetothesystem.Notefreeplayisalsodependentuponproper
adjustmentoftheboosterpushrod.
8/6/2019 Brake Kit Troubleshooting Guide
13/2014
Check Proper Caliper Alignment
Theproperalignmentofthecalipersiscriticaltoasafebrakesystemandinpreventingprematurewear
oftherotorsandpads.Itmaybenecessarytogrindsmallprotrusionsonthecalipertoensureaproper
tandalignmentofthecalipersonthecaliperbrackets.DONOTgrindonthecaliperbrackets,thiswill
weakenthedesignofthebracketsandmayleadtobrakefailure.Beawarethatgrindingcanproduce
atremendousamountofheat.Becauseoftherelativelythinamountofmaterialoftheplate,subjecting
thebracketstothisheatmaycausingthemtobecomebrittleandbreakunderstress.
Ifthewheelangeiswarpedcausingthecaliperandbrackettonotalignproperlywiththerotor,insert
oneortwowashersbetweenthewheelangeandthecaliperbracket.Usethewasherstoshimthe
assemblyandalignwiththerotorasnecessary.
Master Cylinder Test
Notethatthistestofthemastercylinderrequiresacompletere-bleedingofthesystemsincethebrake
linesareremovedfromthemastertoperformthistest.Thisiswhyweincludethistestduringthe
benchbleedingprocess.However,justbecauseyouhaveperformedthetestduringbenchbleeding
doesnotmeanthatairhasnotenteredthe
mastercylindersincethen.Shouldairenter
themastercylinderatanytimeafterbench
bleeding,themastercylinderMUSTbe
removedfromthevehicleandbenchbled
again.Anumberofthingscancauseairto
enterthemastercylinder:
Iftheuidlevelsdroptoolowduringthe
bleedingprocess.
Ifthemastercylinderwasleftsittingfor
toolongafterthebenchbleedingbeforehavingthelinesinstalled.
Mishandlingofthemastercylindersuchasifitweredroppedorjarredexcessively.
Totestthemastercylinder:
1. Removethebrakelinesfromthemastercylinderports.
2. Blockoffthemastercylinderbrakelineportsusingthecorrectsizeinvertedareplugsorboltswith
theappropriatethreadsizefortheportsonyourmastercylinder.Dualportmastercylindersthat
haveportsonbothsidesneedtohaveallfourportsplugged.Theprotrudingconeoftheinverted
areseatinthemastercylinderportismadeofasoftmaterialthatcaneasilybedeformedifover
tightened.Ifusingbolts,besuretojustsnugtheboltssoasnottodamagetheconesealsurface.
Thisconemateswiththeinvertedare(expandedmouthopening)ofthebrakelines.Ifyouhave
theability,youcanalsodrillapointintotheendofthebolttohelppreventthisfromoccurring.Most
GMmastercylindersuse9/16-18threadsforthefrontportsand1/2-20threadsfortherearports.
MostFordmastercylindersuse3/8-24threadsforthefrontportsand7/16-24threadsfortherear
ports.
3. Applyconstantpressuretothepedal,thepedalshouldberm,hardandshouldnotdropovertime.
RearDrumReservoir FrontDisc
FluidReservoir
Secondary
PistonSecondary
PistonSeal
Primary
PistonSeal
PrimaryPiston
8/6/2019 Brake Kit Troubleshooting Guide
14/2015
4. Ifthepedalissquishytheremaybeairinthemastercylinder.Benchbleedthemasteraccordingto
theinstructionsaboveandtestagain.
5. Ifthepedalisrmandthendropsovertimeunderconstantpressure,themastercylindershouldbe
replaced.
Power Brake Booster Test
Ifthepedalfeelshardwhiletheengineisrunning,theboosterisntoperatingcorrectly.Ifyoususpect
theboosterisdefective,donotattempttodisassembleorrepairthepowerbooster.Doingsoisunsafe
andwillvoidyourwarranty.
Test 1
1. Withtheengineoff,pumpthebrake
pedaltoremoveanyresidualvacuumin
thebooster.
2. Holdpressureonthepedalwhileyou
starttheengine.Whentheengine
starts,thepedalshoulddropabouta
1/4,thisindicatesthattheboosteris
workingproperly.
Test 2
1. Runtheengineacoupleofminutes.
2. Turntheengineoffandpressthepedalseveraltimesslowly.Therstpumpshouldbefairlylow.
Thesecondandthirdshouldbecomeslightlyrmer.Thisindicatesanairtightbooster.
Test 3
1. Starttheengineandpressthebrakepedal,thenstoptheenginewiththepedalstillpressed.Ifthe
pedaldoesnotdropafterholdingthepressureonthepedalfor30seconds,theboosterisairtight.
Test 4 - Inspect the Check Valve
1. Disconnectthevacuumhosewhereitconnectstotheintakemanifold.Donotdisconnectthe
vacuumlinefromthebooster.Airshouldnotowwhenpressureisapplied,butshouldowwhen
suctionisapplied.Ifairowsinbothdirectionsorthereisnoairow,thevalveneedstobe
replaced.
Test 5 - Verify Enough Vacuum
1. Checktheoperatingvacuumpressurewhentheengineisatnormaloperatingtemperature.There
shouldbeaminimumof18in.ofvacuum.Vacuummaybeincreasedbyproperlytuningtheengine,
checkingforvacuumleaksandblockagesinvacuumlines.
Vacuumcheckvalve
receivesvacuum
fromtheengine
Hubthat
transfersforce
toMaster
Cylinder
Rubber
diaphragm
Rodfrom
pedal
Poppit
valve
8/6/2019 Brake Kit Troubleshooting Guide
15/2016
Combination Prop Valve Test
1. Useatestlightbyattachingacliptoapositivecontactonthevehicleandtouchthepointofthe
testertotheelectricalconnectionofthecombinationvalve.Ifthelightdoesnotcomeon,thevalve
systemisoperationcorrectlyandnofurthertestingisrequired.
2. Ifthelightdoescomeon,thisindicates
thatthepressuredifferentialvalveisstuckinthefrontorrearposition.
3. Bleedthebrakesystemtodetermineif
thefrontorrearlinesareblockedoff.Set
uponefrontwheelandonerearwheel
forbleedingatthesametime.Crack
bothbleederscrewsandgentlypump
thepedalafewtimes.Theblockedside
willtrickleuidoutwhenthebleeder
screwiscrackedandthepedalpressed.
Anunblockedlinewillsquirtuidoutthe
bleeder.
4. Thelinesthatareclearmustbeleftopenandtheblockedlinesshouldhavethebleederscrews
tighttocausepressuretobuilduponthatside.Besuretousethestandardbleedingproceduresto
preventairfromenteringthesystem.
5. Slowlypressthepedalwithsteadypressureanumberoftimesuntilthelightgoesout;thiswill
centerthedifferentialvalve.Youmayalsohearapopcomefromtheproportioningvalve.Thisisthe
meteringvalvereturningtoitsequalizedposition.Whenthelightgoesout,closethebleederscrew.
Sticking Proportioning Valve
1. Bleedthebrakesystemtodetermineifthefrontorrearlinesareblockedoff.Setuponefrontwheel
andonerearwheelforbleedingatthesametime.Crackbothbleederscrewsandgentlypumpthe
pedalafewtimes.
2. Theblockedsidewilltrickleuidoutwhenthebleederscrewiscrackedandthepedalpressed.An
unblockedlinewillsquirtuidoutthebleeder.
3. Thelinesthatareclearmustbeleftopenandtheblockedlinesshouldhavethebleederscrew
tighttocausepressuretobuilduponthatside.Besuretousethestandardbleedingproceduresto
preventairfromenteringthesystem.
4. Slowlypressthepedalwithsteadypressureanumberoftimesuntilthelightgoesout.Thiswill
centerthedifferentialvalve.Youmayalsohearapopcomefromtheproportioningvalve.Thisisthe
meteringvalvereturningtoitsequalizedposition.Whenthelightgoesout,closethebleederscrew.
ToFrontInfromMC InfromMC
To
Rear
Metering
Valve
ToFront
Combination Valve
8/6/2019 Brake Kit Troubleshooting Guide
16/2017
Brake Fade
Brakefadeisagraduallossofbrakingpowerthatcanbecausedbyoldbrakeuidoroverheated
brakes.Overheatedbrakesisaverydangeroussituationwhichcancauseoldorcontaminated
brakeuidtoboil.Thegasesreleasedfromboilingbrakeuidwillcauseasquishypedalevenafter
thebrakeshavecooledandcancausebrakefailureifnotimmediatelytakencareof.Thisisallthe
morereasontoONLYusebrakeuidthatisfromanewlyopenedsealedcontainer.Drumbrakescan
compoundtheproblemofoverheatedbrakes.Sincethedrumitselfexpandswhenheated,itincreasestheamountoftravelrequiredbytheshoestoeffectivelystopthevehicle.Brakefadecanalsooccurin
drumbrakesbytheaccumulationofwaterinsidethedrumsinceittrapswaterinside.Thewaterthen
actsasalubricantbetweentheshoesandthedrum,causingineffectivebraking.
Typical Brake System Congurations
Figuringouthowtoplumbyourbrakesystemisquitesimple.Thetwoqualifyingquestionsare:
1. Isyourbrakesystem:Disc/Disc,Disc/Drum,orDrum/Drum?Because...
Drumbrakesrequirea10lb.residualpressure(RPV10)tocounteractthespringtensioninthedrumsystemwhichtendstopulltheshoesawayfromthedrums.
DiscBrakesrequireacombinationvalve(oftencalledaproportioningvalve)andsometimesa
2lb.residualvalve-dependingonwhereyourmastercylinderisrelativetoyourcalipers(seenext
bullet).
2. Fordiscapplications;IsyourMasterCylindermountedaboveorbelowyourcalipers?because...
Ifyourmastercylinderisbelowyourcalipersthena2lb.residualvalve(RPV2)isneededto
preventuidfromowingbackfromthecalipersintothemastercylinder.
Quick Reference Guides
1. Drum Brakes Front and Rear with Master on Firewall or Under Floor-Drumbrakesrequirea
10lb.residualpressure(RPV10)tocounteractthespringtensioninthedrumsystemwhichtends
topulltheshoesaway
fromthedrums.Thiswill
giveyoualongerpedal
travelandspongy
brakes.Theresidual
valveholdsapressure
keepingtheshoes
nearthedrumsgiving
ahigherrmerpedal.
Alsorequiredameteringvalve(PVM)tothefront
(themeteringvalve
preventsnosedive).
10lbResidual(RPV10)
Metering
Valve
(PVM)ToRear
10lbResidual(RPV10)
10lbResidual(RPV10)
8/6/2019 Brake Kit Troubleshooting Guide
17/2018
2. Disc Brakes Front and Drums Rear with Master on Firewall-Adisc/drumcombinationvalve
(PV2)istheeasiestwayto
properlybalanceyourbraking
system.Thecombination
valveistwovalvesinone.It
providesmeteringtothefront
whichpreventsnosediveand
proportioningtotherearwhichpreventsrearwheellockup.We
alsorecommendtheadditionof
a10lbresidualvalve(RPV10)to
thereardrumbrakes.
3. Disc Brakes Front and Drums Rear with Master Under Floor-Thebestwaytoplumbadisc/
drumsystemwhenthemasterisundertheooriswithacombinationvalve(PV2)andthena2
poundresidualvalve(RPV2)tothefront
whichisneededto
preventuidfrom
owingbackfrom
thecalipersinto
themaster.We
alsorecommend
theadditionofa10
lbresidualvalve
(RPV10)totherear
drumbrakes.
How to Plumb Your Rod For Disc/Drum System and Master Under Floor
2lbResidual
CombinationValve
10lbResidualMC
RearAxleHoseKit
* With a remote
fll master cylinder
the 2 lb valve to
the front will not be
needed.
10lbResidual(RPV10)
ToRear
ToFront
CombinationValve(PV2)
ToFront 10lbResidual(RPV10)
2lbResidual(RPV2)
ToRearCombinationValve(PV2)
8/6/2019 Brake Kit Troubleshooting Guide
18/2019
4. Four Wheel Disc with Master on Firewall-Thebestwaytoplumbadisc/discsystemwhenthe
masterisontherewalliswithafourwheeldisc
brakecombinationvalve(PV4).
5. Four Wheel Disc with Master Under Floor-Thebestwaytoplumbadisc/discsystemwhen
themasterisundertherewalliswithafourwheeldiscbrakecombinationvalve(PV4)andatwo
poundresidualvalve
(RPV2)tothefrontandatwopound
residualvalve(RPV2)
totherear.
How to Plumb Your Rod For Disc/Disc System and Master Under Floor
2lbResidual
CombinationValve
2lbResidualMC
RearAxleHoseKit
* With a remote
fll master cylinder
the 2 lb valve to
the front will not be
needed.
ToFront
ToRearCombinationValve(PV4)
ToFront 2lbResidual(RPV2)
2lbResidual(RPV2)
ToRear
CombinationValve(PV4)
8/6/2019 Brake Kit Troubleshooting Guide
19/2020
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