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brakes training material -part and service dept.pdf

v vAppropriate service rlEthods and proper rcpair p]ocedures ars essential lor the sab, tdiable op€ration of all molor Yehicles, as “;ii;Jh; p.““““t i“tety of *,e iif ii,iArd doirig the rvork. This manualprori{tes gen€ral direclions br accomplishing servic6 anO repair *rt wigr te$a, etfective techniquea. Follo|ing thom will help assure reliability Ths(e are nud€rous variations in prccsdures, tschniques, tools, and parts lor sewicing \t€hicl€s,.as wsll as in the skill ol the inOi“iOu.i Ooing th. “rork. This marual cannot possibli anticipato all such variations and protide advice or cautions as to each. Ac“;Aingiy;tiygf|e r“no aepa.r“ tror insrruarions pr6uiOea in this marual must lirst establish that h€ compromises neither his personat-silety nor the \rehicle integrity by his choice of mettlods, tools or parts' As ),ou read through th€ p{ocedures, you rvill come across NOTES, CAUTIONS, AND UTAFNINGS. Each one is there lor a “p*ift p.,rp“*. ifOfed giri€ you adAsd intorrnation that will help lou to comptet€^a particular proc€dure. CAUTIoNS are gG; to pr“funtyou lrom riakirg an error that could damage the \€iicle. wARtlttlcs rsmind 'ou lo be especially_carelul in itrose arLas wtreire cardessnssJ can caus€ personal injut Tfte tollorving list conlains some gonoral WARNINGS thal l/ou should lollow when you rrvork on a whicle' . Always wear safety glasses for eye protection. . Use safety stands whenever a procedure requires you to be under the vehicle. . Be sure that the ignition switch is always in the OFF posi- tion, unless otherwise required by the procedure. o Set the parking brake when working on the YeqgLe. lf you have an automatic transmission, set it in PARK unless instructed otherwise for a specific service operation. lf you have a manual transmission, it should be in ifeVenSe (engine OFF) or NEUTRAL (engine ON) unless instructed otherwise for a specific service opera- tion. . Operate the engine only in a well-ventilated area to avoid the danger of carbon monoxide' o Keep yourself and your clothing away from moving. parts when ihe engine is running, especially the fan and belts' . To prevent serious burns, avoid contact with hot metal parts such asthe radiator, exhaust manifold, tail pipe, cat- alytic converter and muffler. . Do not smoke while vrorking on the vehicle. . To avoid injury always remo\€ rings, watches, loose hanging jewelry and loose clothing before beginning to work on a vehicle. Tie long hair securely behind your head. . Keep hands and other objects clear of the radiator fan blades. Electric cooling fans can start to operate at any tinre by an increase in underhood temperatures, even though the ignition is in the OFF position. Therefore, care should be taken to ensure that the electric cooling fan is completely disconnected when working under the hood. IM PORTANT SAFETY NOTICE \// v' The recommendations ard suggosfions contain€d in this manual ars made to assisl the doalsr in improving his d€alorship parls and/ o, ““-i““ deoartnent ooeratib-ns. These recommgndalions ard suggestions do not sup€rsede ot o/orride the provisions of the iv#il-fi'p;ii;y il“rii,“f di tfr“ Srrop L,t“nuat and in arry cases where there may be a conflict, ths pro/isions ol the warrantv and Policy Manual or the Shop Manual shall govern. The descriptions, testing procedures, and specifications in this handbook were in effect at the time the handbook was approved for printing. Ford Motor Company reserves the right to discontinue models at any time, or change specifications, design, or testing pr6cedures without nbtic6 and without inc-urring obligation. Any reference to brand names in this manual is intended merel! as an example oin“ typ“. of tools, lubricants, materials, etc. recommended for use. Equivalents, if available, may be used. The right is reserved to make changes at any time without notice. WARl{lt{G: Marry braks linings contain asbestos fibers. When vrorking on braks compononts, avoid b]oathing trle dust. Brgathing tho asb€stos dust can cause asbestosis and cancor. Breathing asb€stos dusl is harmful to )pur health. Dust and dirt presont on car trrhe€l brake and clutch assgmblies rnay clntain asbeslos libers lhat aro hazardous to your health when mads airborn€ by cleaning with comFssssd air or by dry brushing' Wh€el braks assembliss and clutch lacirEs shouH be cloamd wing a vacuum cleansr rocomnpfibd br use with asb€stos tibers. il;;;;i; J;d O. Oisposea O in a nr.--nn€rthat pre\r€nts dust expooure, such as sealed bags. Th€ bag must be labeled psr OSHA instruc{ions ard the trash haulor notitiod as to th€ contsnts ot the bag lf a vacuum bag suitable ior asbostos is nol available, cleaning should be don€ $€1. ll dust goneration is still possible, technicians should uoar gorornncnt apprc\rod toxic dust puritying respiraiors. OSHA requires areas whero asbestos dust goneration is possiblo to.b€- isolated ard posH with warnirq signs. Only technicians concerned with pgrtorming brako or clutch salvics should be present in the area. \_, --1 Copyright @ 1988 Ford Motor Company\l INTRODUCTION Objectives. How to Use This Manual . . . . .1 STANDARD BRAKE SYSTEM. .....2 Hydraulic Brake System llescription . . . . . . . . .z Friction ........2 TheHydraulicPrinciple ....2 Brakekdal. ....3 BrakeFluid .....4 DualMasterCylinder ......4 BrakingandVehicleWeight .......5 PatkingBrakes .......6 DrumandDisc Brakes. .....7 Ilual ll{aster Cytinder Operation. . . . . . . .9 TlpicalMasrerCylinder ....9 The Reservoir and Compensating Forts . . . . . .10 Operation During Irak Condition. . . . . .n BralreValveOperation... ...14 ProportioningValve .......14 MeteringValve ......14 Height-Sensing Brake-proportioning Valve. . . .15 Pressure Differential Valve. . . . . . .16 Fbont and Rear Disc Brakes . . . . . .lg BasicOperation... .......1g Tlpes of Disc Brakes ......19 PhenolicDiscBrakepistons .....20 R€arDiscBrakes ....20 Rearl)r:umBralreOperation .....22 Tlpes of Drum Brakes . . . . .22 DrumBrakeBuildup ......22 Irading-TrailingBrakes ...23 Duo-Servo (Self-EnergLirg) Action ....25 ParkingMechanism.. .....26 WheelCylinders .....27 Self-AdjustingMechanisms.. ....27 hwerBrakeOperation .....2g VacuumBoost. ......2g Hydro-Boost. . .30 Brakinghsition .....30 Releasedhsition-NoBraking ....31 Accumulator . . .32 Asbestoslt{aterials ....33 Breathing Asbestos Dust . . .33 AreaPreparation ....33 Precautions.. .......33 Diagnosticlests ......34 FedalActionTest. ...34 Warning Lamp Operation Test. . . .34 Brake Fluid kvel Test. . . . .34 AirEntrapmentTest. ......35 Master Cylinder By-pass Test . . . .35 Master Cylinder Non-pressure External I-eakTest. ...36 External Irak Test. . .37 Master Cylinder Compensator Fort Test. . . . . .37 Fower Brake Function Test (Vacuum Booster) . 37 Diagnosis of Conditions Causing Concern . . . .3g Concern Conditions That are Not Brake Related .....39 [,ow Fedal - Brake Larnp On. . . . . . . . .39 Lowkdal -Brake Lamp Otr. .......39 OtherConditions... ......39 BrakesPull . ...40 Hydro-BoostDiagnosis ....40 Bleeding the System . . .43 Orderof Bleeding.. .......43 ManualBleeding ....43 PressureBleeding ....45 Hydro-Boost. .......45 BRAKE NOISE AND VIBRATION D|AGNOS|S . ...46 Normal Bralre Noise Conditions and Causes . .46 Abnormal Brake Noise and Vibration . . .46 Noise at Wheels When Brakes are Applied _ SnapsorClicts ....46 Noise at Wheels When Brakes are Applied _ Scrape or Grind . . .46 Vibration While Vehicle is in Motion . . . . . . . .46 Noise at Wheels When Brakes are Applied _ Squeals, Squeaks, or Chatters . . . . .. 46 Noise at Wheels, Brakes Not Apptied - Squeal or Squeak . .46 .1 I I--Noise at Wheels, Brakes Not Applied - Growling, Clicks or Rattles . . .''''''46 Shop lVlanual Diagnosis Charts ' ' '47 Repairhocedures.. .. “ “ '48 LIGHT TRUCK RABS SYSTEM . ..49 l\{ajorComponentsandLocations . - - ' ' '49 RABSModule ...-..49 Diode/Resistor .-.“'49 Speed Sensor and Excitor Ring ' ' '49 DiagnosticConnector.... “50 Dual SolenoidElectro-HydraulicValve . ' ' ' ' '50 Yellow Rear Antilock Warning Lamp ' ' '51 SensorTestConnector... ... “ “51 SptemOperation... ... “ “52 System and Self-Ibsts “ “ “52 Diagnosisandlbstlng. .““52 WarninglamPs ..“'54 FlashoutCodes ...-..54 Obtaining the Flashout Code . . “ '56 Flashout Code Tests and Diagnostic Tests . . . .58 Rear Antilock Brake SPtem IViringDiagram ““60 HYDRO.MAX POWER BRAKE SYSTEM . ... .62 GeneralDescriPtion.. ... -..62 Mini-MasterCylinder(Split-Brake) ....63 Hydro-MaxBooster... ... -i'r';:'' r;''1-'l'i :=i 1. Review the Table of Contents of this manual, which describes the scope of subject coverage in the fol- lowing major areas: the brake system and subsys- tems; diagnostic tests and diagnosis of conditions causing concern; bleeding brake systems; brake noise and vibration; light truck RABS system and Hydro-Max power brake system. 2. Carefully study the main sections, covering the brake system and subsystems.Understanding and applying this information will help you use the service information in the appropriate Shop Man- ual correctly. 3. Study the other main sections to be aware of diag- nostic and bleeding procedures. 4. When a specific brake system condition is identi- fied, consult the Thble of Contents to locate the information you need to identiff and correct the brake system concerns. Then refer to the Shop Manual for the appropriate repair procedure. WHEEL BRAI(E ASSEMBLIES“ ; AI{D CLUTCII EACINGS SHOTITD .I '$$, CLEAIYED USING A VAC[J[]M CLEAI$ER RECOMMENDED FOR USE WTTTI ASBE$* . TOS F'IBER.S. IXJST AND DIRT:ffIOUtf} BE DISFOSED OF'IN A MAITIITIER TTIAT PREVENTS DUST EXPOSURE,,SUCII AS SEALBD BAGS. ' IIIE BAG .MTIST “ BE' LABELED PER OSHA trTISTRUCTIONS AI{D TIIE TRASH IIAIILER NOTIFIED OF TIIE CONTENTS OF TIIE BAG. . IF A VACT]TIM BAG SUTIABIE FOR ASBESTOS IS NOT AVTIIIABLE, CLEAITI- ING SHOT]LD BE DDTIE WET, IF DTXST GEI{ERATION IS STILL P|OSSIBLE, TECTINIICIANS SH(Xil.,I} IilEAR GOYERhI- . MEhIT-APPROVED TlOXIC DT}ST P{'RT^F II\G RESPIRATORS. . ., : .:...“. ._ OSIIA REQUIRES AREASWIffiRE ATSBF,$ ,'' TOS IXTST GEhIERATION IS POSSTBI,E'IO. BE : ISOLAIED AhlD' FOSIEf),::,\ffiffi : WARNING SIGNS. OhILY TECIU\ilCIAhIS “ CONCERI{ED,, WTTTI. PERFC)RilfII\IG.“ BRAIG OR CTUTCII $DRVICE'SIIC}ULD. BE PFry$EI{T rN TP.flryfi,,,i,_ i,i,,, ,: ,. ' , ,' :HYDRAULIC BRAKE SYSTEM DESCRIPTION Frictlon A brake works by causing friction between a pad or shoe that does not rotate, ffid a disc or drum which revolves with the road wheel. This friction produces the force applied to slow a moving vehicle (or to prevent a station- ary vehicle from rolling). When brakes are applied, the energy of the vehicle is changed into heat. For example, the temperature of the brake linings of a car moving at 60 mph (95 km/h) can rise to 450'F (230'C) during an emergency stop. On a truck, because of the greater weight, the temperature can rise above l000oF (525'C). For this reason the linings of drum and disc brakes must maintain enough friction to provide adequate braking force, yet not so much friction that the linings burn out. The friction is measured as a “coefficient.“ For satisfac- tory perfonnance the friction coefficient of the linings must stay withinnarrorw limits over awide range of tem- peratures. If the friction coefficient stays within these limits, the linings will perform satisfactorily. However, if the linings and drums become overheated the friction coefficient may drop off rapidly, as shown in Figure 1. Figurc I - Fading The unsatisfactory performance is known as “fading.“ On the other hand, the coefficient of friction of some materials increases as the temperature rises. If brake linings were made of these materials, the brakes would “grab“ beyond 300'F (60'C), as shown in Figure 2. COEFFICIENT OF FRICTION 1.0 0.9 0.8 o.7 0.6 0.5 0.4 0.3 o.2 0.1 TEMPERATURE(oC) 40 75 100 125 1s0 17s Figure 2 - Grabbing To avoid both these conditions, the brake linings used on Ford Motor Company vehicle brake systems are designed to have friction coefficients that remain within the limits, across a wide range of temperatures. The Hydraulic Principle Modern brake systems use the hydraulic principle, which works in the following way. A liquid such as hydraulic fluid is virtually incompressible. Pressure applied to the piston of one cytrinder can therefore be transmitted by the hydraulic fluid through lines to a sec- ond piston. The force applied to the second piston is proportional to its surface area. If the second piston is the same size as the first, the force applied to the second piston will be equal. The second piston will also move the same distance as the first, as shown in Figure 3. I) I) Figure 3 - Pistons of Equal Size COEFFICIENT OFFRICTION 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 # :: ; ,.:.}i TEMPERATURE(oC)40 75 100 125 1s0 17s 200'v If the second piston has a larger surface area than the first, the force applied will be proportionally greater. However, the second piston will move a shorter dis- tance. For example, in the system illustrated in Figure 4, a main cylinder supplies three pistons. A force of 10 lb acts on piston A, which has an area of 2 nf . The pressure generated in cylinder A is therefore 5 psi. Now look at the three output pistons. Each is acted on by 5 psi inter- nal pressure. The middle piston, C, has an area of 2 irf , so it produces an output force of 10 lb. Piston B, how- ever, has an area of 4 fuf , so it produces 20 lb of force. Piston D, with 1 in'z of surface area produces 5 lb of force. The same pressure acting over a different area produces a different force. In a vehicle brake system there is a main cylinder which supplies four output pistons. The forces produced by the output pistons are proportional to their surface areas. Brake Pedal When the brake pedal is depressed, force is applied to the master cylinder. On a basic hydraulic brake system (where there is no power assist) the force applied is transmitted mechanically. As the pedal in Figure 5 piv- ots at point A, the force applied to the brake pedal is multiplied mechanically. The force that the pushrod applies to the master cylinder piston is therefore much greater than the force applied to the brake pedal. Figure 5 - Brake Pedal Action This force is transmitted by hydraulic pressure from the master cylinder to each of the wheel cylinders. This pressure is maintained as long as the brake pedal remains depressed. The hydraulic lines are made of steel. Hydraulic lines made of other materials should not be used on Ford Motor Company vehicles. froru t 20lb I 10lb I slb Figure 4 - Typical Pistons of Dlffercnt Sizes
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