Peterbilt 348 2017 - Operating the Brake System

OPERATINGTHEBRAKESYSTEM
OPERATINGTHE
BRAKESYSTEM
Introduction
Thisvehicle’sbrakesystemfunctions
withtheuseofcompressedair
generatedfromtheengine’sair
compressor.Thecompressedairis
storedinvariousairtankstoensure
thatairpressureisavailablewhenever
thedriverneedsit.
Compressedairisdeliveredtothe
brakesystemthroughthevalveat
thebrakepedalandiscontrolled
withvariousvalvesandbraking
circuits.Thebrakesystemisdesigned
withseparatefront,rearand(when
applicable)trailercircuitssothatifone
circuitiscompromisedandlosesair,
theothercircuitswillnotbeaffected.
Safetyvalvesineachcircuitwillprotect
theothercircuitsintheeventthata
circuitlosesair.
Theaircompressorontheenginewill
typicallyprovide100-130psi(690-896
kPa)totheairtanks.Thevehicle
isalsodesignedwithanairdryer,
whichremovesmoisturefromthe
compressedairinordertoprotectall
componentsintheairsystem.
Thebrakesystemmaybefurther
enhancedbyadditionaldevices
suchasbrakeproportioningvalves,
Anti-lockbrakingsystemsorsensors
designedtoletyouknowifyourbrake
padsneedtobeserviced.
Certainconditionsmayresultinthe
brakesurfacesgettingwet.Brake
surfacesthatarewetdonotperform
aswellaswhentheyaredry.There
maybesituationswherewetbrake
surfacescannotbeavoided.Insuch
situations,applythebrakeswhilein
motion,todrythebrakesurfaces.
Certainconditionsmayresultinyour
brakesurfacesbecomingoverheated
(above800°For427°C).Overheated
brakeswilldamageliningsand
drumsurfaces,ultimatelydecreasing
brakingperformance.Referto
RetardersandDescendingagradeto
avoidoverheatingthebrakes.
Thisvehiclemaybeequippedwith
ananti-lockbrakingsystem(ABS).
ThisABSreducesthepossibilityof
wheellock-up.Ifawheelisabout
tolockduringbraking,theABSwill
automaticallyadjustairpressuretothe
brakechambersontheappropriate
wheel(s)topreventwheellock-up.The
ABSisautomaticallyturnedonwhen
theignitionswitchisturnedon.
4-24Y53-6060-1C1(03/17)
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