Page 409 of 3229

Publi s hed: 11-May-2011
Brake System - General Information - Brake System
Diagnosi s and Tes ti ng
Principle of Operation
For a detail ed descripti on of the brake s ys t em, refer t o t he rel evant Des cript ion and Operat ion secti on in the workshopmanual. REFER to:
Brake Syst em (206-00 Brake Sys t em - General Informat ion, Des cript ion and Operat ion),Front Dis c Brake (206-03 Front Di sc Brake, Des cri pt ion and Operati on),Rear Di sc Brake (206-04 Rear Di s c Brake, Des cri pti on and Operati on),Parking Brake (206-05 Parki ng Brake and Actuat ion, Descri pti on and Operat ion),Hydraul ic Brake Act uati on (206-06 Hydraul ic Brake Act uati on, Des cript ion and Operat ion),Brake Boost er (206-07 Power Brake Act uat ion, Des cript ion and Operat ion).
Inspection and Verification
1. Verify t he cus t omer concern.1.
2. Vis ually ins pect for obvious s igns of damage and s ys t em i ntegri ty.2.
Visual Inspection
MechanicalElectricalBrake mast er cyl inderBrake cali per pi st on(s )Brake di scsW heel bearingsBrake padsPower brake boos t erVacuum pumpBrake pedal li nkageBrake boos ter vacuum hos eTires
Damaged or corroded wiring harnes sBrake mas ter cyli nder fluid level s wi tch
3. If an obvious cause for an obs erved or report ed concern is found, correct t he caus e (if pos s ible) beforeproceeding t o t he next s t ep.3.
4. If t he caus e is not vis ually evi dent , verify t he concern and refer t o t he Sympt om Chart.4.
Road Test
Carry out a road tes t to compare act ual vehicl e braking performance wi th the performance s t andards expected by t hedri ver. The abi li ty of t he t est driver to make val id compari s ons and det ect performance defi cienci es wil l depend onexperience.
The dri ver s hould have a t horough knowl edge of brake s ys t em operat ion and accept ed general performance guideli nes tomake good comparis ons and detect performance concerns .
An experienced brake t echnician will al ways es t abl is h a route that wi ll be us ed for all brake di agnos is road t es t s . Theroads s elected will be reasonably s moot h and level. Gravel or bumpy roads are not sui table because the s urface does notall ow t he ti res t o grip t he road equall y. Crowned roads s houl d be avoided becaus e of t he large amount of wei ght s hifted tot he low set of wheels on t his type of road. Once the route is es tabl is hed and cons ist ent ly us ed, the road s urface vari ablecan be eli minat ed from t he t es t resul ts .
Before a road tes t, obt ain a compl et e des cript ion of t he cus t omer concerns or s uspected condit ion. From t he des cript ion,t he techni cian's experience wi ll all ow t he techni cian t o mat ch pos s ibl e caus es wi th s ympt oms. Certai n components wil l bet agged as pos si ble s us pect s whil e others wil l be eli minated by the evidence. More i mport ant ly, t he cus t omer des cri pt ioncan reveal uns afe condit ions which s hould be checked or correct ed before the road t est . The descri pti on wil l als o help formt he bas i c approach t o t he road tes t by narrowi ng t he concern t o s peci fi c components , vehicle s peed or condit ions .
Begin t he road tes t wit h a general brake performance check. Keepi ng t he des cri pti on of the concern in mind, t est t hebrakes at different vehicle s peeds usi ng both light and heavy pedal pres s ure.
If the concern becomes evident duri ng thi s check, verify it fit s t he descri pti on given before the road t est . If t he concern isnot evi dent , att empt to dupl icate t he condi ti on us ing t he informat ion from the des cri pt ion.
If a concern exi st s , refer t o t he Symptom Chart.
Symptom Chart
SymptomPossible CauseAction
Brakes nois yBrake padsBrake dis csGO t o Pinpoint Test A.
Vibrati on when brakes areappliedW heels /t ires out of bal anceW heel hub nut s loos eBrake cal iper mounti ng bolt s loos eBrake padsForeign mat eri al /s crat ches /corrosi onon brake dis c contact surfacesExcess i ve brake dis c t hicknes s
GO t o Pinpoint Test B.
Page 410 of 3229

1
1
SymptomPossible CauseAction
variat ionExcess i ve brake dis c runoutW heel beari ng wear or fail ureSus pensi on bushi ng wear or failureSt eeri ng bus hing wear or failure
The brakes pull or dri ftTi re pres sures/wearBrake cal ipersBrake padsBrake dis csW heel al ignment adjus tmentW heel beari ngSus pensi on bushi ngs and bal l joint s
GO t o Pinpoint Test C.
The pedal feels s pongyAir in brake s ys t emLeak i n hydraulic sys temBrake boos t er/mas ter cyl inderfail ureBrake pads
GO t o Pinpoint Test D.
The pedal goes down fastAir in brake s ys t emLeak i n hydraulic sys temBrake boos t er/mas ter cyl inderBrake pads
GO t o Pinpoint Test E.
The pedal goes downs lowl yAir in brake s ys t emBrake boos t er/mas ter cyl inderGO t o Pinpoint Test F.
Exces s ive brake pedaleffortBrake padsBrake boos t erGO t o Pinpoint Test G.
Brake l ockup duri ng li ghtbrake pedal forceBrake padsBrake cal ipersGO t o Pinpoint Test H.
Brakes dragParking brake controlappl ied/mal functi onSei zed parking brake cablesSei zed cal iper sl ide pi nsSei zed brake cal iperBrake boos t erPedal gear
GO t o Pinpoint Test I.
Exces s ive/Errat ic brakepedal t ravelHydraul ic s ys temBrake padsBrake dis csHub and bearing as s embly
GO t o Pinpoint Test J.
The red brake warni ngi ndi cat or is always onFl uid l evelBrake fl uid l evel s ensorParking brake controlEl ect ri cal circui t
Fi ll the sys tem t o s pecificati on. Check for l eaks .Ins tall a new brake mas t er cyli nder fluid res ervoiras requi red.REFER t o: Brake Mas ter Cyli nder (206-06 HydraulicBrake Act uati on, Removal and Ins tal lati on).Check parking brake operat ion/elect rical circui ts .REFER t o: Parking Brake (206-05 Parki ng Brake andAct uat ion, Diagnosi s and Test ing).
Slow or incompl ete brakepedal returnBrake pedal bindi ngBrake boos t er/mas ter cyl inderGO t o Pinpoint Test K.
Pinpoint Tests
PINPOINT TEST A : BRAKES NOISY
T ESTCO NDIT IONSDET AILS/RESULT S/ACT IONS
A1: INSPECT BRAKE PADS
Ins pect the condi ti on of the front and rear brake pads . Check for damage to any ant i-s queals hims .
Are the brake pads OK?YesGO to A2.NoCLEAN or INSTALL new brake pads as requi red.REFER to: Brake Pads (206-03 Front Di sc Brake, Removal and Ins tal lati on) /Brake Pads (206-04 Rear Di s c Brake, Removal and Ins t allat ion).Test t he s yst em for normal operat ion.
A2: INSPECT BRAKE DISCS
Ins pect the brake di s cs for exces si ve corros ion, wear or di s c thi ckness variat ion.
Does exces si ve corros ion, wear or di s c thi ckness variat ion exis t?YesINSTALL new brake di s cs and brake pads as required.REFER to: Brake Pads (206-03 Front Di sc Brake, Removal and Ins tal lati on) /Brake Di sc (206-03 Front Di s c Brake, Removal and Ins t allat ion) /
Page 411 of 3229

1
1
1
1
1
1
1
1
Brake Pads (206-04 Rear Di s c Brake, Removal and Ins t allat ion) /Brake Di sc (206-04 Rear Dis c Brake, Removal and Ins tal lati on).TEST the sys tem for normal operat ion.NoVehicle i s OK.
PINPOINT TEST B : VIBRATION WHEN BRAKES ARE APPLIED
T ESTCO NDIT IONSDET AILS/RESULT S/ACT IONS
B1: ROAD T EST VEHICLERoad tes t t he vehi cl e between 40-80 km/h (25-50 mph) wit hout applying brakes .
Is t he vibrati on pres ent ?YesTEST for nois e vibrat ion and hars hnes s (wheel /t ire balance, worn/damaged s us pensi onbus hings /component s , etc.). REPEAT road t es t i f neces sary.NoGO t o B2.B2: CHECK FOR BRAKE VIBRAT ION
Road tes t t he vehi cl e between 40-80 km/h (25-50 mph) wit h li ght and medium appli cat ion on thebrake pedal .Is a vibrat ion pres ent?YesCHECK the brake cal iper mounti ng bol ts and wheel hub nuts and TIGHTEN as necess ary. CHECK t hebal ance of al l road wheels and t ires and REPAIR as necess ary. CHECK t he brake di scs for excess i vewear, runout, t hicknes s vari ati on or cracks . INSTALL new brake di s cs and brake pads as required. GOto B3.NoVehi cl e i s OK.B3: IS VIBRAT IO N ST ILL PRESENT UNDER BRAKE APPLICAT ION?
Road tes t t he vehi cl e between 40-80 km/h (25-50 mph) wit h li ght and medium appli cat ion on thebrake pedal .Is a vibrat ion pres ent?YesCHECK for wear or fai lure of s t eering gear bushi ngs . CHECK for wear or fai lure of s teeri ng gear balljoi nt s . CHECK for wear or fail ure of front wheel bearings, s us pens ion bus hings and ball joints . CHECKfor wear or fail ure of rear wheel bearings , s us pensi on bushi ngs and bal l joint s . REFER t o relevants ect ion i n works hop manual and INSTALL new components as required.NoVehi cl e i s OK.
PINPOINT TEST C : THE BRAKES PULL OR DRIFT
T ESTCONDIT IONSDET AILS/RESULT S/ACT IONS
C1: ROAD T EST VEHICLE
Road t es t t he vehi cle and apply t he brake pedal.
Does the vehicl e pull or drift ?YesGO to C2.NoVehicle is OK.C2: INSPECT T IRE CONDIT ION/PRESSURE
Check for exces s ive t ire wear or i ncorrect pres sures.
Are the t ires at t he correct pres sure and i n good condit ion?YesGO to C3.NoADJUST the ti re press ures or INSTALL new ti res i f exces si vel y worn. TEST t he s ys t em for normaloperat ion.
C3: CHECK CALIPERS
Check the di sc brake cal iper pis tons and pi ns for binding, leaking or s t icki ng.
Do t he dis c brake cali per pi st ons and pins bi nd, l eak or s t ick?YesRECTIFY s t icking pins and INSTALL new brake calipers as required.REFER to: Brake Cal iper (206-03 Front Dis c Brake, Removal and Inst all ati on) /Brake Cal iper (206-04 Rear Di sc Brake, Removal and Ins tal lati on).TEST t he sys t em for normal operat ion.NoGO to C4.
C4: INSPECT BRAKE DISCSCheck the brake di s cs for exces si ve damage, t hicknes s vari ati on or runout .
Does exces si ve damage or runout exi st ?YesINSTALL new brake dis cs and brake pads as required. TEST t he s ys t em for normal operati on.NoGO to C5.
C5: INSPECT T HE FRONT HUB AND WHEEL BEARING ASSEMBLYCheck the front hub and wheel bearing as s embl y.
Page 412 of 3229

1
1
1
1
2
3
4
5
6
7
1
1
Are the wheel bearings OK?YesGO to C6.NoINSTALL new wheel bearings as requi red.REFER to: Front W heel Beari ng (204-01 Front Sus pensi on, Removal and Ins t al lat ion).TEST t he sys t em for normal operat ion.
C6: CHECK SUSPENSION BUSHINGS AND BALL JOINT S
Check al l s us pensi on bushi ngs and bal l joint s.
Are the s us pens ion bus hings and ball joints OK?YesCheck and adjust s t eering geomet ryREFER to: Four-W heel Alignment (204-00 Suspens ion Sys tem - General Informati on, GeneralProcedures ).NoINSTALL new sus pens i on bus hings and ball joints as required. REFER t o t he rel evant sect ion i n t heworks hop manual.
PINPOINT TEST D : THE PEDAL FEELS SPONG Y
T ESTCONDIT IO NSDET AILS/RESULT S/ACT IO NS
D1: CHECK FOR SPONGY PEDAL (ENGINE OFF)
Check for a fi rm brake pedal.
Is t he brake pedal effort and brake pedal t ravel normal?YesVehi cl e i s OK.NoGO t o D2.
D2: CHECK BR AKE PEDAL RESERVE (ENGINE OFF)Pump t he brake pedal 10 t imes and hol d on t he final appli cat ion.
Does t he brake pedal feel fi rm on final appl icat ion?YesGO t o D3.NoBLEED the brake sys tem.REFER t o: Brake Sys tem Bleeding (206-00 Brake Sys tem - General Informat ion, GeneralProcedures ) /Brake Syst em Press ure Bleeding (206-00 Brake Sys tem - General Informat ion, General Procedures ).D3: CHECK BR AKE PEDAL RESERVE (ENGINE ON)
Appl y Parking Brake and ens ure transmis s ion i s in park/neutral .
Start engine and al low to idle.
Appl y t he brake pedal l ightl y t hree or four t imes .
W ait 15 seconds for t he vacuum t o recover.
Pus h down on the brake pedal unti l it s tops movi ng downward or an increas ed res i st ance to t hebrake pedal t ravel occurs .Hold t he brake pedal in t he applied pos it ion whi le increasi ng t he engi ne s peed t o 2000 rpm.
Rel ease the accel erat or pedal.
Does t he brake pedal move downward as t he engine s peed ret urns t o idl e?YesGO t o D4.NoCHECK the vacuum t o brake boos ter.
D4: CHECK BR AKE FLUID LEVELCheck t he brake mas t er cyli nder reservoi r fl ui d l evel.
Is t he fluid level OK?YesBLEED the brake sys tem.REFER t o: Brake Sys tem Bleeding (206-00 Brake Sys tem - General Informat ion, GeneralProcedures ) /Brake Syst em Press ure Bleeding (206-00 Brake Sys tem - General Informat ion, General Procedures ).TEST the s ys tem for normal operat ion.NoCHECK for l eaking brake s ys t em and RECTIFY as necess ary. ADD fl ui d and BLEED t he brakesys t em.REFER t o: Brake Sys tem Bleeding (206-00 Brake Sys tem - General Informat ion, GeneralProcedures ) /Brake Syst em Press ure Bleeding (206-00 Brake Sys tem - General Informat ion, General Procedures ).TEST the s ys tem for normal operat ion. REPEAT road tes t i f required.
PINPOINT TEST E : THE PEDAL GOES DOWN FAST
T ESTCONDIT IO NSDET AILS/RESULT S/ACT IONS
E1: ROAD T EST VEHICLE
Road t es t the vehicle and appl y the brake pedal .
Is t he brake pedal effort and brake pedal t ravel normal?YesVehi cl e is OK.NoGO t o E2.E2: PRESSURIZE SYST EM AND CHECK BRAKE PEDAL T RAVEL
Page 413 of 3229

1
1
1
1
1
2
3
4
1
2
3
4
1
W it h t he vehi cle s t at ionary pump t he brake pedal rapi dly (fi ve ti mes ).
Does t he brake pedal travel build up and t hen hol d?YesBLEED t he brake s ys tem.REFER t o: Brake Syst em Bleedi ng (206-00 Brake Sys tem - General Informati on, GeneralProcedures ) /Brake Sys t em Press ure Bleeding (206-00 Brake Sys tem - General Informat ion, General Procedures ).TEST t he s yst em for normal operati on.NoGO t o E3.
E3: CHECK FOR BRAKE SYST EM LEAKS
Check for ext ernal brake sys t em l eaks . For addit ional informati on, refer t o brake mas t er cyli ndercomponent tes t in this secti on.
Are l eaks found?YesREPAIR as neces s ary, ADD fluid and BLEED brake s ys t em.REFER t o: Brake Syst em Bleedi ng (206-00 Brake Sys tem - General Informati on, GeneralProcedures ) /Brake Sys t em Press ure Bleeding (206-00 Brake Sys tem - General Informat ion, General Procedures ).TEST t he s yst em for normal operati on.NoSys tem is OK.
PINPOINT TEST F : THE PEDAL GOES DOWN SLOWLY
T ESTCONDIT IONSDET AILS/RESULT S/ACT IONS
F1: CHECK FOR BRAKE SYST EM LEAKS
Check for ext ernal brake s yst em leaks . For addi ti onal i nformat ion, refer to brake mas ter cyl indercomponent t es t i n t hi s s ect ion.
Are there any ext ernal brake s ys t em l eaks ?YesREPAIR as neces sary. ADD fl uid and BLEED t he brake s yst em.REFER to: Brake Sys t em Bleeding (206-00 Brake Sys t em - General Informat ion, GeneralProcedures) /Brake Sys tem Pres s ure Bl eeding (206-00 Brake Sys t em - General Informat ion, General Procedures).TEST the sys tem for normal operat ion.NoCheck for brake mas t er cyli nder i nt ernal leaks, refer t o brake mas t er cyli nder component t est int hi s s ect ion, and repair as necess ary.
PINPOINT TEST G : EXCESSIVE BRAKE PEDAL EFFORT
T ESTCO NDIT IONSDET AILS/RESULT S/ACT IONS
G1: CHECK BR AKE PADSCheck t he brake pads for wear, contaminati on, correct i nst all at ion, damage and t ype.
Are any concerns found?YesINSTALL brake pads correctl y or INSTALL new brake pads as requi red.REFER t o: Brake Pads (206-03 Front Dis c Brake, Removal and Ins tall ati on) /Brake Pads (206-04 Rear Di sc Brake, Removal and Ins tal lat ion).TEST the s ys tem for normal operat ion. REPEAT road tes t .NoGO t o G2.G2: CHECK VACUUM
Dis connect the vacuum hose from t he brake boos ter.
Connect a vacuum/pres sure t est er to the vacuum hose.
Run the engine at normal operati ng temperat ure.
Record the vacuum readi ng.
Is t he readi ng 90 kPa (26.5 in-Hg) or greaterYesGO t o G3.NoLO CATE and REPAIR t he s ource of low vacuum. TEST t he s yst em for normal operati on.
G3: INSPECT SYST EM
Swit ch the engine off.
Reconnect t he vacuum hos e.
Ins pect t he brake boos ter, rubber grommet, and al l vacuum plumbi ng for cracks, hol es, damagedconnect ions , or mis s ing clamps .
Pump t he brake pedal s everal ti mes t o exhaus t the vacuum. Pus h down on the brake pedal andhol d.
Does the brake pedal move down when t he engi ne is st art ed?YesVacuum sys tem is OK.NoGO t o G4.G4: CHECK PO WER BRAKE BOOST ER VALVE
Check t he brake boost er val ve. For addit ional i nformati on, refer to Brake Boost er component tes t i nthi s s ect ion.
Page 414 of 3229

1
1
1
1
1
1
1
2
Is t he power brake boost er val ve OK?YesCHECK the brake boos t er. For addit ional informat ion, refer t o Brake Boos t er component t es t in t hissect ion. INSTALL a new brake boos ter as requi red.REFER t o: Brake Boos ter (206-07 Power Brake Act uati on, Removal and Ins tal lati on).TEST the s ys tem for normal operat ion.NoINSTALL a new brake boos t er valve. TEST the sys tem for normal operat ion.
PINPOINT TEST H : BRAKE LOCKUP DU RING LIG HT BRAKE PEDAL FORCE
T EST CONDIT IONSDET AILS/RESULT S/ACT IONS
H1: T EST BRAKE LOCKUPRoad t est t he vehicle and apply the brake pedal li ght ly.
Do t he brakes l ockup?YesGO to H2.NoVehicle is OK.
H2: INSPECT BRAKE PADS
Inspect brake pads for contami nat ion, correct ins t al lat ion, damage and type.
Are any concerns found?YesINSTALL t he brake pads correct ly or INSTALL new brake pads as required.REFER t o: Brake Pads (206-03 Front Di s c Brake, Removal and Ins t allat ion) /Brake Pads (206-04 Rear Dis c Brake, Removal and Inst all ati on).TEST t he s ys t em for correct operati on.NoGO to H3.
H3: INSPECT BRAKE CALIPERSInspect brake calipers for bindi ng, l eaking or s t icking.
Are any concerns found?YesINSTALL t he brake cali pers correct ly or INSTALL new brake cal ipers as required.REFER t o: Brake Caliper (206-03 Front Dis c Brake, Removal and Ins tall ati on) /Brake Cal iper (206-04 Rear Di sc Brake, Removal and Ins t al lat ion).TEST t he s ys t em for normal operati on.NoVehicle is OK.
PINPOINT TEST I : BRAKES DRAG
T ESTCONDIT IONSDET AILS/RESULT S/ACT IONS
I1: ROAD T EST VEHICLE
Road t es t t he vehi cl e and apply t he brakes .
Are the brakes funct ioning correct ly?YesVehicle i s OK.NoGO to I2.
I2: CHECK BRAKE CALIPERS AND PARKING BRAKE CABLES
Check the front and rear cali per pis t ons and pins for bi ndi ng, l eaki ng or st icking and parki ng brakecabl es for s t icki ng/binding.
Do t he dis c brake cali per pi st ons and pins bind, l eak or s t ick, or t he parking brake cabl es st ick/bi nd?YesREPAIR or INSTALL new components as required. Tes t the s ys tem for normal operat ion. Road tes tvehi cle i f neces sary.NoGO to I3.
I3: CHECK BRAKE BO OST ER
Check the brake boos ter connecti ng rod alignment and t ravel.
Is the connect ing rod OK?YesVehicle i s OK.NoINSTALL a new brake boost er.REFER to: Brake Boos t er (206-07 Power Brake Actuat ion, Removal and Ins t allat ion).TEST the sys tem for normal operat ion.
PINPOINT TEST J : EXCESSIVE/ERRATIC BRAKE PEDAL TRAVEL
T ESTCONDIT IONSDET AILS/RESULT S/ACT IONS
J1: T EST ON ROUGH ROAD
Road t es t the vehicle on rough road condit ions .
Apply the brakes s l owly.
Is t he brake pedal effort and brake pedal t ravel normal?YesVehicl e is OK.NoGO t o J2.
J2: CHECK BRAKE FLUID LEVEL
Page 415 of 3229

1
1
2
3
4
5
6
1
1
2
3
4
5
1
Check t he brake mas ter cylinder res ervoir flui d level.
Is t he fl uid l evel OK?YesGO t o J3.NoCHECK brake mas ter cyl inder res ervoir s ealing poi nts . For addit ional informat ion, refer t o Brakemast er cyl inder component t es t in t his secti on. ADD brake fluid and BLEED t he brake s ys tem.REFER t o: Brake Syst em Bl eedi ng (206-00 Brake Syst em - General Informati on, General Procedures )/Brake Sys t em Pres s ure Bleedi ng (206-00 Brake Sys tem - General Informati on, General Procedures ).TEST t he s yst em for normal operati on. REPEAT road tes t if neces s ary.J3: CHECK BRAKE PEDAL RESERVE
Run engine at idle speed.
Apply the brake pedal li ght ly three or four ti mes .
W ait 15 s econds for the vacuum t o repl eni sh.
Pus h down on t he brake pedal unt il i t s tops moving downward or an increas ed res is t ance t o t hebrake pedal t ravel occurs .
Hol d t he brake pedal i n t he appl ied pos it ion whi le i ncreas i ng the engine speed t o 2000 rpm.
Rel eas e t he accel erator pedal .
Does t he brake pedal move downward as t he engi ne s peed returns to idle?YesGO t o J4.NoCHECK the vacuum t o the brake boos t er.
J4: CHECK T HE FRO NT WHEEL BEARING ASSEMBLY
Check t he front wheel bearing as s embly.
Are t he front wheel beari ngs l oose?YesINSTALL a new front wheel beari ng if damaged.REFER t o: Front W heel Bearing (204-01 Front Suspens ion, Removal and Inst all at ion).TEST t he s yst em for normal operati on.NoCHECK the front brake di scs for thicknes s variances .
PINPOINT TEST K : SLOW OR INCOMPLETE BRAKE PEDAL RETU RN
T ESTCONDIT IO NSDET AILS/RESULT S/ACT IO NS
K1: CHECK FOR BRAKE PEDAL RET URN
Run the engine at i dle whi le maki ng s everal brake appli cat ions .
Pul l the brake pedal rearward wi th approxi matel y 44.5 N (10lb) force.
Rel eas e t he brake pedal and measure t he dis tance t o t he toe board.
Make a hard brake appl icat ion.
Rel eas e t he brake pedal and measure t he brake pedal t o t oe board di st ance. The brake pedalshould return t o it s original posi ti on.
Does t he brake pedal return t o it s original posi ti on?YesVehi cl e is OK.NoGO t o K2.
K2: CHECK FOR BRAKE PEDAL BINDINGDis connect t he brake boos ter from the brake pedal. Check t he brake pedal t o ens ure freeoperat ion.
Is t he brake pedal operat ing freel y?YesINSTALL a new brake boos ter.REFER t o: Brake Boost er (206-07 Power Brake Act uat ion, Removal and Ins tall ati on).TEST t he s yst em for normal operati on.NoREPAIR or INSTALL new brake pedal. TEST t he s ys t em for normal operati on.
Component Tests
Brake Booster
1. Check al l hos es and connecti ons . All unus ed vacuum connect ors s houl d be capped. Hos es and thei r connect ionss hould be correctl y s ecured and in good condi ti on wit h no hol es and no col laps ed areas. Ins pect t he val ve on t hebrake boos ter for damage.
1.
2. Check t he hydraulic brake s ys t em for leaks or low flui d.2.
3. W i th the aut omat ic trans mi s si on in PARK, s t op the engine and apply the parki ng brake. Pump t he brake pedals everal ti mes t o exhaus t all vacuum in the s ys tem. W it h t he engi ne s wit ched off and al l vacuum i n t he s ys t emexhaus t ed, apply the brake pedal and hold i t down. St art t he engi ne. If t he vacuum sys tem is operat ing, t hebrake pedal wil l tend t o move downward under cons t ant foot pres sure. If no mot ion is felt , the vacuum boos t ers ys tem is not funct ioning.
3.
4. Remove the vacuum hos e from t he brake boos ter. Mani fol d vacuum should be avai lable at t he brake boos ter endof t he hose wit h t he engi ne at idl e s peed and t he automat ic trans mi ss i on in PARK. Make s ure that all unusedvacuum outl ets are correct ly capped, hos e connectors are correct ly secured and vacuum hoses are i n goodcondit ion. W hen it is es tabli s hed that manifold vacuum is avai lable t o t he brake boos ter, connect t he vacuumhos e t o t he brake boost er and repeat St ep 3. If no downward movement of the brake pedal is felt , ins tal l a new
4.
Page 416 of 3229

brake boos ter.
5. Operate the engine for a minimum of 10 s econds at a fast i dle. Stop the engine and al low t he vehicle t o s t andfor 10 mi nut es. Then, appl y the brake pedal wi th approxi mately 89 N (20lb) of force. The pedal feel (brakeappli cat ion) s houl d be t he s ame as t hat not ed wit h t he engine runni ng. If the brake pedal feel s hard (no poweras s is t), ins t al l a new valve and t hen repeat t he tes t. If t he brake pedal s t ill feels hard, i ns t all a new brakeboos ter. If t he brake pedal movement feel s s pongy, bleed t he brake s ys t em.REFER t o: Brake Syst em Bl eedi ng (206-00 Brake Syst em - General Informati on, General Procedures ) /Brake Sys t em Pres s ure Bl eedi ng (206-00 Brake Syst em - General Informati on, General Procedures ).
5.
Brake Master Cylinder
Us ual ly, t he fi rs t and s tronges t indicat or of anything wrong i n t he brake s ys t em i s a feeling through t he brake pedal. Indiagnosi ng the condit ion of t he brake mas t er cyli nder, check pedal feel as evidence of a brake concern. Check for brakewarni ng lamp ill uminat ion and t he brake fluid level i n t he brake mas t er cyli nder reservoi r.
Normal Condit ions
The fol lowing condit ions are cons idered normal and are not i ndi cat ions t hat t he brake mast er cyl inder i s i n need of repair.
Modern brake sys tems are des igned t o produce a pedal effort that is not as hard as in the pas t . Compl aint s of lightpedal effort s s houl d be compared t o t he pedal efforts of another vehi cl e of t he s ame model and year.The fl uid l evel wi ll fal l wit h brake pad wear.
Abnormal Condi ti ons
Changes i n t he brake pedal feel or brake pedal travel are indicators t hat s omet hi ng coul d be wrong in the brake sys tem.The diagnost ic procedure and techni ques us e brake pedal feel , warning i ndi cat or il lumi nat ion and l ow brake flui d level asindicat ors t o diagnosi ng brake s yst em concerns . The foll owing condi ti ons are consi dered abnormal and indi cat e t hat t hebrake mas t er cyli nder i s in need of repai r:
• NOTE: Pri or to carrying out any diagnosi s , ens ure the brake sys tem warni ng indicator i s functi onal .
Brake pedal goes down fast . This could be caus ed by an external or int ernal leak.Brake pedal goes down s l owl y. Thi s coul d be caused by an int ernal or external l eak.Brake pedal is l ow or feels spongy. Thi s condit ion may be caus ed by no fl ui d i n the brake mas ter cylinder, reservoi rcap vent holes cl ogged or air i n t he hydraul ic s ys tem.Brake pedal effort is excess ive. This may be caus ed by a bi nd or obs t ructi on in the pedal/li nkage, a faul tynon-ret urn val ve, boost er or ins ufficient boos t er vacuum.Rear brakes lock up during light pedal force. Thi s may be caus ed by damaged brake pads , a parti ally appl ied parkingbrake, a damaged ABS s ens or or bearing fail ure.Brake pedal effort errat ic. This condit ion could be caus ed by the brake boos t er or incorrectl y ins tal led brake pads .Brake warning i ndi cat or is on. This may be caus ed by low fl uid l evel or fl oat as s embly damaged.
Non Pressure Leaks
Any reduced fl uid volume in t he brake mast er cyl inder res ervoi r may be caused by two types of none pres sure externalleaks .
Type 1: An ext ernal leak may occur at the brake mast er cyl inder res ervoir cap because of incorrect posi ti oning of t hegasket and cap. Repos it ion cap and gasket .
Type 2: An ext ernal leak may occur at the brake mast er cyl inder res ervoir mounti ng seal s. Repair s uch a l eak by ins tall ingnew s eals and make s ure that t he brake mas t er cyli nder reservoi r ret ai ning bolt i s correct ly i nst all ed.