Peterbilt 348 2017 - Hydraulic Brakes

OPERATINGTHEBRAKESYSTEM
HydraulicBrakes
WARNING!
Donotoperatethevehicleinthe
eventofamalfunctioninanyairor
hydrauliccircuit.Suchamalfunc-
tionmaypreventthebrakesystem
fromoperatingproperly,andcould
resultinaninjuryaccident.Theve-
hicleshouldnotbeoperateduntilthe
systemisrepairedandbothbrak-
ingcircuits,includingallpneumatic,
hydraulic,andmechanicalcompo-
nentsareworkingproperly.
Theoperationofthevehicle'sbraking
systemisbasedontheprincipleof
hydraulics.Hydraulicactionbegins
whenforceisappliedtothebrake
pedal.Thisforcecreateshydraulic
pressureinthemastercylinderandis
ampliedwithassistanceofapower
booster.Thesupplementalboostin
forceisdevelopedwhenpressurized
powersteeringuidfromthesteering
pumppressesonthemastercylinder
piston.Asasafetyprecaution,the
pressurizeduidfromthemaster
cylinderhastwomutuallyindependent
circuits.Theprimarycircuitsupplies
thefrontwheelswhilethesecondary
circuitsuppliestherearwheels.The
displaceduidfromthemastercylinder
travelsthroughbrakepipesterminating
atthewheelcylinderswhichactuate
thebrakepadmechanisms.Actuation
ofthesemechanismsforcethebrake
padsagainsttherotorstostopthe
wheels.
Areserveelectricmotorpumpprovides
aredundantpowersourceforthe
hydraulicboosterintheeventnormal
owfromthepowersteeringpumpis
interrupted.Manualbrakingisalso
availableintheeventboththepower
andreservesystemsareinoperative.
WARNING!
Neverdriveyourvehiclewiththe
parkingbrakesapplied.Alwaysre-
leasetheparkingbrakespriorto
movingthevehicle.Failuretodis-
engagetheparkingbrakespriorto
movingyourvehiclecouldresult
inexcessiveheatbuild-upofthe
brakesandstartare.
NOTE
Today’sdieselelectronicengines
havesignicanttorqueandstarta-
bilitypoweratlowRPM.Combina-
tionsofenginespeedandavailable
torquemayover-powerthevehicle’s
parkingbrakes.
(03/17)Y53-6060-1C14-35
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