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790/795/797 Series
Jacobs Engine Brake™
INST
ALLA
TIO
N M
AN
UA
L
� INSTALLLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™
Table of Contents
PageSection 1: Introduction 4-5HousingIdentification 4EngineIdentification 4SpecialTools 5RecommendedTorqueValues 5EngineCovers 5
Section 2: Engine Preparation 6-7Series 60 Engines with DDEC IV & VUndercoverWireHarnessInstallation(Retrofit) 6
Section 3: Brake Housing Installation 8-10SlavePistonAdjustment 10
Section 4: Engine Brake Controls 11
Section 5: Engine Brake Operational Check 12RockerCoverInstallation
Section 6: Engine Brake Maintenance 13-19TheoryofOperation 13ExhaustBlowdown 13PartIdentification 14ControlValve 15SlavePistonAdjustingScrew 16SolidScrew 16SolenoidValve 16MasterPiston 17-18SlavePiston 19
INSTALLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™ 3
General Information
TheseinstructionsdescribetheinstallationoftheModel790/795/797SeriesJacobsEngineBrake™,designedfortheDetroitDieselSeries60®engine.Forspecificapplicationinformationandslavepistonclearancesettings,refertotheJacobsEngineBrakeforDetroitDieselEnginesApplicationGuide,P/N�4770,whichcanbefoundonwww.jakebrake.com.
Foradditionalinformationonthe790/795/797Seriesenginebrakes,refertotheSeries60EngineServiceManual,P/N6SE483.
UseOSHA-approvedcleaningsolventforcleaningparts.Originalpartstobereusedshouldbeinspectedforwearandreplacedasrequired.Besuretocoatpartswithcleanengineoilwhenreinstallingthem.
ThestandardJacobsVehicleSystemsWarrantyappliestotheinstallationofaJakeBrake®Kit.ThewarrantyisadministeredbyDetroitDieselCorporation.ForspecificwarrantycoveragespleasecontactDetroitDiesel.
Safety PrecautionsThefollowingsymbolsinthismanualsignalconditionspotentiallydangeroustothemechanicorequipment.Readthismanualcarefully.Knowwhentheseconditionscanexist.Thentakenecessarystepstoprotectpersonnelaswellasequipment.
THISSyMBOLWARNSOFPOSSIBLEPERSONALINJURy.
THISSyMBOLREFERSTOPOSSIBLEEqUIPMENTDAMAGE.
NOTE: INDICATESANOPERATION,PROCEDUREORINSTRUCTIONTHATISIMPORTANTFORCORRECTSERVICE.
Fuels,electricalequipment,exhaustgasesandmovingenginepartspresentpotentialhazardsthatcouldresultinpersonalinjury.Takecarewheninstallingequipmentorparts.Alwayswearsafetyglasses.Alwaysusecorrecttoolsandfollowproperproceduresasoutlinedinthismanual.
NOTE:
NOTE:
THEJACOBSENGINEBRAKEISAVEHICLESLOWINGDEVICE,NOTAVEHICLESTOP-PINGDEVICE.ITISNOTASUBSTITUTEFORTHESERVICEBRAKINGSySTEM.THEVEHI-CLE'SSERVICEBRAKESMUSTBEUSEDTOBRINGTHEVEHICLETOACOMPLETESTOP.
NEVERREMOVEORADJUSTANyENGINEBRAKEORCOMPONENTWITHTHEENGINERUNNING.
4 INSTALLLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™
Section 1: Introduction
HousingIdentificationThemodel,partnumber,serialnumber,andadjust-mentinformationarelocatedonthenameplateatthetopofeachhousing.(SeeFig.1andFig.�)
Fig1
Fig�
Fig3
EngineIdentificationEnginemodelidentification,serialnumberandmodelnumber,areonthenametaglocatedonthesideofthevalvecoverandstampedonthecylinderblockbeneaththeintakemanifold.(SeeFig.3)
INSTALLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™ 5
SpecialTools
General18mm-1�pointSocket10mm-1�pointSocket6"Extension13mmWrenchRetainingRingPliers(.047"diameter,45˚)DiagonalWireCutter
KentMooreRockerShaftLiftingTool P/NJ-35966AStudTorqueSocket P/NJ-44706AMasterPistonAssemblyTool P/NJ-45976(Model797Only)
DetroitDieselSeries60EngineServiceManual
JacobsFeelerGage,0.0�0"(0.508mm) P/N017�78FeelerGage,0.0�6"(0.660mm) P/N017671FeelerGage,0.03�"(0.813mm) P/N030504ControlValveCoverRemovalTool P/N016978
RecommendedTorqueValues
HousingHold-down CapScrews 80lb.-ft.(108N-m)
(lubricatedwithengineoil)
RockerShaftHold-downStud 100lb.-ft.(136N-m)
SlavePistonAdjusting ScrewLocknut 336lb.-in.(38N-m)
SolenoidValve 110lb.-in.(1�.4N-m)
SlavePistonSpring ShoulderBolt �00lb.-in.(�3N-m)
EngineCoversTheenginebrakehasbeendesignedtofitontheSeries60enginewithnoadditionalvalvecovers.Onenginesequippedwithatwo-piecealuminumvalvecover,itisNOTnecessarytoremovethelowervalvecovertoinstalltheenginebrake.However,onestyleuppervalvecovermayrequiremodificationatthebreatherhousinglocation(inside)forenginebrakeclearance.
NOTE:
Fig4
IFINTERFERENCEEXISTSBETWEENTHEFRONTENGINEBRAKEHOUSINGANDTHEROCKERCOVERCAPATTHEBREATHERHOUSINGLOCATION,GRINDTHEUPPERCOVERTOPROVIDECLEARANCE.CLEANCOVERTHOROUGHLyAFTERGRINDING.
6 INSTALLLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™
AccessEngineOverhead
1. DisconnectBattery
FAILURETODISCONNECTBATTERyMAyCAUSEECMDAMAGE.
�. Thoroughlycleanengine
3. Removevalvecoverandgasket.
NOTE: IFTHEENGINEHASATWO-PIECECOVER,THELOWERVALVECOVERBASEDOESNOTHAVETOBEREMOVED.
ExchangeWireHarness
1. Removeexistinginjectorharness&mountingclipsfromcylinderhead.
a.Separatewireharnessfromcylinderhead
retainingclips.b.Remove�harnessmountingboltsfromrear
ofcylinderheadatheadpassthroughholes.(SeeFig.5)
NOTE: FORADDITIONALACCESSTOREARCyLINDERHEADPASSTHROUGH,THEROCKERSHAFTSMAyBEREMOVEDUSINGKENTMOORETOOL#J35996A
Section 2: Engine PreparationSeries 60 Engines with DDEC IV & V
c.Disconnect10pinwiresocketlocatedonintakesideofcylinderblockbelownumbersix(6)intakeport.(SeeFig.6)
d.Removeharnessbymanipulatingharness throughcylinderheadpassthroughatrear
ofhead.
e.Removeharnessretainingclipsfrom threadedholesinheadanddiscardclips.
(SeeFig.7)
Fig5
Fig6
Fig7
REMOVEENTIRECLIPS,HOLESWILLBERE-USEDFORJACOBSSUPPLIEDHOUSINGHOLDDOWNBOLTS
NOTE:
INSTALLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™ 7
Fig8
�. InstallnewharnessP/N�3536019foron-highwayapplicationsorP/N�3534�44foroff-highwayapplications
a.Manipulateharnessthroughrearheadpass
through.Routeharnessconsistentto previousharness.
TAKECARENOTTODAMAGEWIRINGORCONNECTORS
b.Connectnewharnesstoinjectors.
c.Connect10pinwiringsockettomainengineharnessandsecureharnesswithplasticwiretiesasnecessarytobrakespacertubes(referenceFig11inSection3forimage). d.Secureharnessatrearheadpassthroughwith�mountingbolts.
HARNESS IS NOW READY FOR JAKE BRAKE INSTALLATION
8 INSTALLLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™
Section 3: Brake Housing Installation
InstallEngineBrakeHousings
1. RemoveRockerShaftAssembliesusing18mmSocketandKentmoore#J-35996A
NOTE:
WEARSAFETyGLASSESWHILEBLOWINGTHEOILFROMTHEBOLT
HOLES.
a.RemoverockerarmholddownboltsM1�x100mmlong(6).
b.Removerockerarmnutsatfrontandrearofhead(�).
c.Retorquerockershaftstudslocatedatfrontandrearofcylinderheadat100lb.-ft.(136N-m)withKentmooretool#J-44706A.(SeeFig.9)
�.SetRockerShaftAssembliesbackoncamcaps.
Fig9Fig11
3.Setfront&rearJakeBrakehousingsonrockershaftslocatingonretorquedstuds.Ensurethatmasterpistonpushrodswillengagewithpocketlocatedontopofinjectorrockerarm(seeFig.10).
4.PositionJakeBrakemountingspacertubesunderouterhousingmountinglegs.(SeeFig.11)
NOTE: TOPREVENTDAMAGETOWIREHARNESS,RUNWIRESINBOARDOFSPACERTUBESANDSECURETOTUBESUSINGPLASTICWIRETIES.
Fig10
REMOVINGTHEOILFROMTHEBOLTHOLESPREVENTSTHECyLINDERHEADFROMCRACKINGWHENBOLTSARETIGHTENED.ATTACHALENGTHOFTUBINGTOANAIRGUNNOZZLEANDBLOWOUTTHEOILFROMTHEROCKERSHAFTHOLD-DOWNBOLTHOLES.COVERTHEHOLESWITHHANDTOWELSTOMINIMIZEOILSPRAy
INSTALLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™ 9
Fig15
5. InstallJacobssuppliedmountingbolts,twolengths,andoriginalDDCstudhexnutsremovedearlier.(SeeFig.1�)
A-M1�x140mm-usedontheexhaustsideoftheengine
B-M1�x170mm-usedonintakeside(solenoidside)ofengine
NOTE:
NOTE:
Fig1�
Fig13
Fig14
6. TorquedownbrakehousingpersequenceinFig.14at80lb.-ft.(108N-m).
7.VerifyexhaustandintakevalvelashisstillwithinDDCspecificationsforengine.Ifvalvelashisoutoftolerance,refertoDDCmanualforresettingprocedure.
8.Attachsolenoidwirestosolenoidandengagewiresinwireretainerclip.(SeeFig.15)
NOTE:
BEFORETORqUINGENSURETHATWIREHARNESSISINBOARDSOASTONOTINTERFEREWITHVALVECOVER
BEFORETIGHTENINGHOLDDOWNBOLTS,MOVETHEHOUSINGFROMSIDETOSIDEANDTHENLOCATEHOUSINGINCENTEROFTRAVEL.(SEEFIG.13)
A
B
797BAPPLICATIONSUTILIZEADDCWIREHARNESSTRAyWHICHISAT-TACHEDONTOTHEREARBRAKEHOUSING.
REFERENCETHEDDCSERIES60ENGINESERVICEMANUALP/N6SE483FORPROPERTRAyTORqUINGPRO-CEDURE
10 INSTALLLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™
4. Rechecklashsettings.Iflashsettingisincorrect,repeatsteps(1)through(3)above
NOTE:
MODEL 795/797 SERIES
1. Backouttheadjustingscrewsontheslavepistonsuntiltheslavepistonsdonottouchtheexhaustrockerarmadjustingscrews.
�. Inserttheproperfeelergage(correctadjustmentisonhousingdatatag)betweentheslavepistonandtheexhaustrockeradjustingscrew.Usinga3/16"(inch)hexwrenchturnintheadjustingscrewuntiltheslavepistoncontactstheexhaustrockeradjustingscrewthroughthefeelergage,andadragisfeltonthegage.
3. Holdtheadjustingscrewinplaceandtorquethelocknutto38N•m(336lb-in).Rechecklashsettings.Iflashsettingisincorrect,repeatsteps(1)through(3)above.
Adjust Slave Piston Clearance
FAILURETOFOLLOWADJUSTMENTPROCEDURESCANRESULTINENGINEORENGINEBRAKEDAMAGE.
NOTE: MAKESLAVEPISTONADJUSTMENTWITHTHEENGINESTOPPEDANDCOLD.ADJUSTEACHCyLINDERWITHTHEEXHAUSTVALVESINTHECLOSEDPOSITION.
NOTE: REFERENCEJACOBSAPPLICATIONGUIDEP/N�4770FORPROPERENGINEANDBRAKESPECIFICLASHSETTINGS.
MODEL 790 SERIES
1.Backouttheadjustingscrewsontheslavepistonsuntiltheslavepistondoesnottouchtherockerarmadjustingscrew.
�. Inserttheproperfeelergage(correctadjustmentisonhousingdatatag)betweentheslavepistonandtheexhaustrockeradjustingscrew.Usinga3/16"(inch)hexwrench,turnintheadjustingscrewuntiltheslavepistoncontactstheexhaustrockeradjustingscrewthroughthefeelergage.Continueturningintheadjustingscrewuntilthevalvespringsbegintocompress,thenturninone(1)additionalturn.Waitatleast30secondsforoiltobepurgedfromtheJ-Lashadjustingscrew.
NOTE: ALLOILMUSTBEPURGEDFROMTHEJ-LASHADJUSTINGSCREW.IFOILISBELOW60°F,16°C,WAITATLEASTTWOMINUTESFOROILTOBEPURGEDFROMTHEJ-LASHADJUSTINGSCREW.
SERIOUSENGINEDAMAGEMAyOCCURFROMIMPROPERLASHSETTING.
3. Afterthetimeintervalspecifiedinstep(�),backouttheadjustingscrewONLyuntilalightdragisfeltonthefeelergage.Donotretractmore than required to obtain a light drag on the feeler gage. Hold the J-Lash adjusting screw inplaceandtorquethelocknutto38N•m(336lb-in).
NOTE: IFTHEJ-LASHADJUSTINGSCREWISBACKEDOUTUNTILITNOLONGERCOMPRESSESTHESLAVEPISTONSPRING,OILWILLENTERTHESCREWANDTHEADJUSTMENTWILLBEINCORRECT.IFTHISOCCURS,REPEATSTEPS(1)AND(�).
OVERTORqUEOFLOCKNUTWILLPROHIBITPROPERJ-LASHOPERATION
Fig16
ONCETHEENGINEBRAKEHASBEENRUNyOUWILLNOTBEABLETOCHECKTHEEN-GINEBRAKEADJUSTMENT.THISISBECAUSEOFOILRETAINEDINTHEJ-LASHADJUSTINGSCREW.IFUNSUREOFTHEADJUSTMENT,yOUMUSTREPEATSTEPS(1)THROUGH(4)ABOVE.
INSTALLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™ 11
Section 4: Engine Brake Controls Series 60 Engines with DDEC IV & DDEC V
ONSERIES60ENGINESEqUIPPEDWITHDDECIVORV,THEENGINEBRAKEISCONTROLLEDByTHEDDECECM.USEOFAJACOBS'SUPPLIEDCONTROLMODULEISNOTREqUIRED.
CONTACTyOURVEHICLEOEMWITHyOURVEHICLESERIALNUMBERFORBILLOFMATERIALSNEEDEDFORINSTALLATION.
Jacobs Dash Switch (optional)
(mayuseinplaceofVOEMswitch)
1. Locateanareaonthedashforthedashswitchgroup,JacobsP/N0�0035,anddrilla�"hole.
�. PasstheloosewiresofthevehicleOEMwireharnessthroughthe�"holefromthebacktothefront
3. Attachthewireharnesstotheswitchterminalsontheswitchgroupp/n0�0035.
4. Installtheswitchassemblywiththebracket,lockwashersandwingnuts(seeFig.18).
DONOTOVERTIGHTENNUTS.SWITCHFAILURECOULDRESULT!
NOTE: CONTACTVEHICLEOEMFORINSTALLATIONDETAILSANDWIRINGDIAGRAMOFTHEWIRINGHARNESSANDINTERFACEWITHDASHCONTROLSWITCH.
Fig17
1� INSTALLLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™
Two-piece Rocker Cover Installation
1. Makesurethesealisinplaceintherockercoverbaseandsetthecoverinplaceonthecoverbase.
�. Installtheboltwithaflatwasher,isolatorandlimitingsleeveintothecoverholes.
3. Tightentheboltsto14N•m(10lb-ft)inthesequenceshowninFig.1.
4. Torquetheboltsto�7N•m(�0lb-ft).
Road Test the Vehicle.
1. Roadtestthevehicle.TheenginebrakeshouldcomeonwhentheswitchisintheONposition,theclutchisengagedandnothrottleisbeingapplied.
Section 5: Engine Brake Operational Check
Bleed the engine brake housings
1. Besurewiresareawayfrommovingparts.
�. Starttheengineandallowtorunforafewminutes.
3. Manuallyactivatethesolenoidvalveseveraltimestoallowthehousingtobefilledwithoil.
NOTE: THESOLENOIDVALVEISMANUALLyACTIVATEDByDEPRESSINGTHEARMATUREPINLOCATEDINTHECENTERONTOPOFTHESOLENOID.
Check for proper operation.
1. Manuallyactivatethesolenoidvalveandwatchthemasterpistonstobesuretheyaremovingdownintothepocketintheinjectorrockerarm.
�. Watchtheslavepistons.Theyshouldmovedowntocontacttheexhaustvalverockerarmadjustingscrews.
3. Checkeachhousingtobesureitisfunctioning.
4. Shutdownengine.
Rocker Cover Installation
One-piece Rocker Cover Installation
1. Installthesealintothegrooveinthecoverandsetthecoverinplaceonthecylinderhead.
�. Installthefourretainingboltswithisolatorsandwashers.
3. Startingwiththecenterboltsandworkingoutward,tightentheboltsto��N•m(16lb-ft).
4. Presstheprotectiveplugsintothetwocenterholes.
SERIES60ROCKERCOVER
Fig18
INSTALLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™ 13
Section 6: Engine Brake Maintenance
TheoryofOperation
Energizingtheenginebrakeeffectivelyconvertsapower-producingdieselengineintoapower-absorbingaircompressor.Thisisaccomplishedthroughmotiontransferusingamaster-slavepistonarrangementwhichopenscylinderexhaustvalvesnearthetopofthenormalcompressionstroke,releasingthecompressedcylinderchargetoexhaust.
Theblowdownofcompressedairtoatmosphericpressurepreventsthereturnofenergytotheenginepistonontheexpansionstroke.Theeffectofthisactionisanetenergyloss,sincetheworkdoneincompressingthecylinderchargeisnotreturnedduringtheexpansionprocess.
ExhaustBlowdown
Referringtotheschematicdrawingbelow,exhaustblowdownoccursasfollows:
1. Theenergizedsolenoidvalve(A)permitsenginelubeoil(B)toflowunderpressurethroughthecontrolvalve(C)toboththemasterpiston(D)andtheslavepistons(E).
�. Oilpressurecausesthemasterpistontomovedown,comingtorestintheinjectorrockerarmrecess(pocket).
A
B CENGINE OIL IN
ENGINE OIL OUT
EE
FF
D
Fig19
3. Theinjectorrockerarmbeginsitstravelasinthenormalinjectioncycle,movingthemasterpistonupwardanddirectinghighpressureoiltotheslavepiston.Theballcheckvalveinthecontrolvalveimprisionshighpressureoilinthemaster-slavepistonsystem.
4. Highpressureoilcausestheslavepistonstomovedown,momentarilyopeningtheexhaustvalves(F),whiletheenginepistonisnearitstopdeadcenterposition,releasingcompressedairtotheexhaustmanifold.
5. Compressedairescapestotheatmosphere,completingacompressionbrakingcycle.
14 INSTALLLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™
NEVERREMOVEANyENGINEBRAKECOMPONENTWITHENGINERUNNING.PERSONALINJURyMAyRESULT
TheJacobsEngineBrakeistypicallyatrouble-freedevice.However,inspectionsarenecessaryandsomemaintenanceisrequired.Usethefollowingprocedurestokeeptheenginebrakeintopcondition.
Thissectioncovershowtoproperlyremove,cleanandreinstallenginebrakecomponents.UseanOSHA-approvedcleaningsolventwhenwashingparts.Besuretocoatpartswithcleanengineoilwhenreinstallingthem.
Fig18
1SolenoidValve�Seal,SolenoidUpper3Seal,SolenoidCenter5MasterPiston6MasterPistonPushrod7MasterPistonSpring8MasterPistonRetainer9SpiroloxRing(797)9SnapRing(790/795)10AdjustingScrewLockNut11SolidScrew(795/797)11J-Lash(790)1�SlavePiston13SlavePistonSpringGroup17RetainingRing18Washer19InnerControlValveSpring�0OuterControlValveSpring�1ControlValve��PipePlug�3DriveScrew�4WireHarnessClip�5CapScrew�6CapScrew�7SpacerTube
PARTS LISTINGFig�0
INSTALLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™ 15
ControlValve
REMOVECONTROLVALVECOVERSCAREFULLy.CONTROLVALVECOVERSAREUNDERLOADFROMTHECONTROLVALVESPRINGS.REMOVEWITHCARETOAVOIDPERSONALINJURy.
1. Pressdownoncontrolvalvewasherusingthecontrolvalvecoverremovaltool,Jacobsp/n16978torelievespringpressure(SeeFig.�1)
�. Removeretainingringusingretainingringpliers(SeeFig.�1).
3. Slowlyremovecoveruntilpressureceases,thenremovethetwocontrolvalvesprings.
4. Usingneedle-nosepliers,reachintotheboreandgraspthestemofthecontrolvalve.Removethecontrolvalve.
Fig�1
Fig��
Fig18
5. WashthecontrolvalveswithapprovedcleaningsolventPushawirethroughtheholeinthebottomofthevalvetoinsurethattheballcheckisfree(seeFig.��).Theballshouldliftwithlightpressureonthewire.Iftheballisstuckinthevalve,thecontrolvalveshouldbereplaced.Drythevalvewithcompressedairandwipecleanwithapapertowel.
6. Thoroughlycleanthecontrolvalveboreinthehousingusingcleanpapertowels.
7. Dipthecontrolvalvesincleanlubeoil.Holdingthevalvebythestem,guideitintotheborethenallowthevalvetodecendtothebottomoftheborebyitsownweight.Ifbindingoccurs,thecontrolvalveshouldbereplaced.Reassemblepartsreversingtheremovalprocedure.Besureretainingringearsarerotated90º(degrees)afterinstallationtoensurefullengagement.
16 INSTALLLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™
SlavePistonAdjustingScrew
MODEl790SERIES
1. LoosentheslavepistonadjustingscrewlocknutandremovetheJ-Lashadjustingscrewfromthehousing.Cleaninapprovedcleaningsolvent.
�. InspecttheJ-Lashassemblytoassuretheplungerisretainedinthescrewbody,bypullingontheplungerwithfingers.Theplungershouldretractsmoothlyandcompletelyunderpressureifnotreplaceentireassembly.
NOTE:AMODERATETOHEAVySPRINGFORCEWILLBEPRESENTBEHINDTHEPLUNGERIFOILISSTILLTRAPPEDINTHEASSEMBLy.
3. PlacetheJ-Lashassemblyintotheslavepistonadjustingscrewboreandreplaceadjustingscrewlocknut.
NOTE:DONOTEXCEEDLOCKNUTTORqUE.THISWILLHINDERPLUNGERMOVEMENTANDCAUSEENGINEBRAKEPERFORMANCEPROBLEMS.
SolidScrew
MODEl795/797SERIES
1. Removethesolidscrews.
�.Cleanthesolidscrewsinapprovedcleaningsolvent.Inspectforexcessivewearordamage.Replaceifnecessary.
Fig�4
SolenoidValve
DONOTDISASSEMBLEORTAMPERWITHTHESOLENOIDVALVE.ENGINEDAMAGECOULDRESULT.
1. Disconnectsolenoidvalveharness.Using3/4"socketandextension,unscrewsolenoidvalve.
�. Removeanddiscardthetworubbersealrings.Iftheringsstayinthehousingbore,removewithapieceofwire.
3. Washoutthesolenoidvalvewithapprovedcleaningsolvent.Useabrushtocleantheoilscreen.Risethesolenoidvalveincleaningsolvent.
4. Cleanoutthesolenoidvalveboreinthehousing.Usecleanpapertowels.Neveruserags,astheymayleavelintandresiduewhichcanplugtheoilpassageways.
5.Coatnewsolenoidvalvesealringswithcleanlubeoil.Installthesealringsontothesolenoidvalvebody.Becarefulnottotwistthesealwhileinstalling.
6.Besurethesealsareseatedproperly.Carefullyscrewthesolenoidvalveintothehousingwithoutunseatingtheseals.Torquethevalveto110lb.-in.(1�.4N-m).
Fig�3
INSTALLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™ 17
MasterPiston
MODEl790/795SERIES
1. Compressmasterpistonretainerandremovesnapringusingretainingringpliers(.047"diameter,45˚).(SeeFig.�5)
REMOVESNAPRINGCAREFULLy.MASTERPISTONISUNDERLOADFROMTHESPRING.REMOVEWITHCARETOAVOIDPERSONALINJURy.
�. Removemasterpistonpushrod,retainer,springandmasterpiston.
3. Cleanthemasterpistoninapprovedcleaningsolvent.Inspectforexcessivewearordamage.Replaceifnecessary.Inspectthemasterpistonbore.Somewearmarksarepermissible.Applycleanlubeoiltothepistonandinsertintobore.Masterpistonshouldmoveinandoutfreelywithnobinding.Ifbindingoccurs,replacemasterpistonand/orhousing.
5. Reassemblethemasterpiston,pushrod,spring,andretainerinhousing.Besuretorotatesnapring90º(degrees)afterinstallation.
NOTE:THESPRINGSHOULDHOLDTHEMASTERPISTONCOMPLETELyINTHEHOUSING.IFNOT,THESPRINGHASRELAXEDANDMUST
BEREPLACED.
NOTE:THESMALLERDIAMETERENDOFTHESPRINGENGAGESTOTHEMASTERPISTONPUSHRODBALLEND.SPRINGMUSTNOTEXPANDOVERBALLEND.
MODEl797SERIES
1. Usemechanic'spicktowedgescrewdriverbladebeneathspiroloxring(SeeFig.�6).
�.Rotatescrewdriverarounddiametertounwindspirolox.Removeanddiscardspiroloxring-itcannotbereused(SeeFig.�7).
REMOVESNAPRINGCAREFULLy.MASTERPISTONISUNDERLOADFROMTHESPRING.REMOVEWITHCARETOAVOIDPERSONALINJURy.
3.Removemasterpistonpushrod,retainer,springandmasterpiston.
4. Cleanthemasterpistoninapprovedcleaningsolvent.Inspectforexcessivewearordamage.Replaceifnecessary.Inspectthemasterpistonbore.Somewearmarksarepermissible.Applycleanlubeoiltothepistonandinsertintobore.Masterpistonshouldmoveinandoutfreelywithnobinding.Ifbindingoccurs,replacemasterpistonand/orhousing.
Fig�5
Fig�6
Fig�7
18 INSTALLLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™
5.Reassemblemasterpiston,pushrod,spring,retainer,andspiroloxringinhousingusingmasterpistonassemblytoolJ-45976.(SeeFig.�8)
NOTE:WHENPLACINGRETAINERINTOBORE-PARTNUMBERSHOULDBEVISIBLE.
a.Loadspiroloxintotapperedring.(SeeFig.�9)
b.Engagemasterpistonassemblytoolintobore.Ridgewillengagewithborechamfer.
c.Pushdownonspiroloxuntilitsnapsintoplace.(SeeFig.31)
NOTE:THESPRINGSHOULDHOLDTHEMASTERPISTONCOMPLETELyINTHEHOUSING.IFNOT,THESPRINGHASRELAXEDANDMUST
BEREPLACED.
NOTE:THESMALLERDIAMETERENDOFTHESPRINGENGAGESTOTHEMASTERPISTONPUSHRODBALLEND.SPRINGMUSTNOTEXPANDOVERBALLEND.
Fig30
Fig�9
Fig�8Fig31
INSTALLATIONINSTRUCTIONSFOR790/795/797SERIESJACOBSENGINEBRAKES™ 19
Fig30
SlavePistons
1. Removeslavepistonshoulderbolts.
NOTE:SPRINGPRESSUREWILLBERELEASEDASBOLTISREMOVED.THEREWILLBENOSPRINGPRESSUREREMAININGPRIORTOBOLTBEINGCOMPLETELyDISENGAGED.
�. Removesprings,bridge,andslavepistons.
3. Cleantheslavepistonsinapprovedcleaningsolvent.Inspectforexcessivewearordamage.Replaceifnecessary.
4.Ensureslavepistonborehasnoburrsorridges,ifsoremovewithamachinistdeburringtool.Donothonetheslavepistonbore.Removaloftoomuchmaterialwillreducebrakingperformance.
5. Reassemblecomponents.Torqueshoulderbolt�00lb.-in.(�3N-m).
OVERTORqUEWILLFRACTUREBOLT.
JacobsVehicleSystems��EastDudleyTownRoadBloomfield,CT0600�
VisitusontheInternet:www.JAKEBRAKE.COM
P/N�9901Rev.B ©�004JacobsVehicleSystems,Inc. PrintedinU.S.A. Rev.1�/06