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Check system for leaks visually. If problem is related tohydraulic ser Check system for leaks visually. If problem is related tohydraulic ser

Check system for leaks visually. If problem is related tohydraulic ser - PDF document

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Uploaded On 2016-08-06

Check system for leaks visually. If problem is related tohydraulic ser - PPT Presentation

Important Follow these steps carefully to prevent damage to master cylinder seals1 Loosen brake line at master and have assistant push pedal down approximately 12 inch andhold in that position2 ID: 434816

Important: Follow these steps carefully

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Check system for leaks visually. If problem is related tohydraulic service just performed, then bleed using Õs procedures.If system has open-face master, then pump pedal upand check for gyser when pedal is released quickly. Ifgyser is present, that circuit of hydraulic system has air.If problem is still present after above steps, then proceedwith flowchart. This flowchart covers most vehicles andsystems, but is not meant to be all inclusive. Use boxesnext to each step to chart path taken. It is sometimesnecessary to retest to ensure accurate results. Important: Follow these steps carefully to prevent damage to master cylinder seals.1. Loosen brake line at master and have assistant push pedal down approximately 1/2 inch andhold in that position.2. Install line locks on each brake hose in hydraulic system Ñ use only approved type.3. Have assistant depress brake pedal and hold pressure on system Ñ while pressure is on sys-tem, try and rotate each tire. If line locks are installed properly, tires will spin freely. If tire will notspin or drags, repeat steps 1 and 2. 4. Have assistant continue to hold pressure on pedal wile performing the steps below. kT Condition 1Condition 2 With the line locks installed,pedal is high and hard System is good from mastercylinder to line locks. Problemis at one or more of the wheels.To isolate the problem, followthe procedure below. If wheels are properly isolated, the problem is infront of line locks, between 1. Remove brake lines from master cylinder.2. Install plugs or dummy lines in master cylinder.3. Bleed at each outlet fitting using single stroke method, making sure notto exceed 3/4 pedal travel. With line locks installed,pedal is still low or spongy Is vehicle equipped with RWor RABS Note: For RWAL/RABS-equipped vehicles, checkEH valve for by-passing dump valve.Cylindrical Body Valve: Remove accumulator capscrew and spring. Have assistant apply brakewhile holding screwdriver against accumulatorpiston. If piston moves during brake apply, dumpvalve is leaking and valve needs to be replaced.Block Style Valve: Remove rubber dust cap fromaccumulator cap screw. Insert paper clip until itbottoms against accumulator piston. Have assis-tant apply brake while holding screwdriveragainst accumulator piston. If piston moves dur-ing brake apply, dump valve is leaking and valveneeds to be replaced.See June 1999 issue, page 44 for more details 1.2: DETERMINE TYPE OF HYDRAULIC SYS- Front to rearsplit system Diagonalsplit system Quick-Take-UpMaster Cylinder With brake pedalstill depressed,remove line lockon rear brake With brake pedalstill depressed,remove line lock onright rear brake Afailed QTU valve can cause a, spongy pedal on vehiclesequipped with QTU master cylin-ders. Diagnosis of the QTU valve isnot straight forward.Best method of diagnosis is to usea process of elimination. Follow thesteps below.1. Is low pedal gone with line lockson front brake hoses?2. If no, then problem is not in frontbrakes or QTU valve. If yes, thencheck for all conditions listed¥ Air at front brakes;¥ Binding or incorrectly installe¥ Seized sliders or pads;¥ Separated linings;¥ Excessive rust build-up behindpads or shims;¥ Excessive wheel bearing play;¥ Ballooning brake noise.If any of the above is found, thencorrect and retest. If none of theabove is found, then problem ismost likely a by-passing or non-functioning QTU valve. Replacemaster cylinder and bleed accord-ing to manufacturerÕs instructions. 1.2A: Check Pedal Condition With brake pedalstill depressed,remove line lockon rear brake 1.2B: Check Pedal Condition Pedal is lowor spongy Pedal ishigh and Pedal is lowor spongy Problem is not inrear brake circuit,problem is one orboth front brakes.With brake pedal stilldepressed, removeright front line lock. Rear brake(s) are causing pedal condition.Check the following possible causes (Drum Brakes):¥ Rear brake and parkingbrake adjustment;¥ Drum size and ¥ Lining condition; and¥ Excessive wheelbearing play. 1.2C: Check Pedal1.2D: Check Pedal Pedal ishigh and Pedal is lowor spongy Problem is not inright front wheel.With brake pedalstill depressed,remove left frontline lock. This condition should not. If pedal is high andhard with all line locksremoved, then problemmay be intermittent.Retest and if pedal isgood, test drive vehicle. If when either one or both of the front line locks areremoved the low-pedal condition is duplicated, thencheck for the following possible causes:¥ Proper caliper installation (bleeders at highest point);¥ Pad installed wrong, binding on guide rails, or friction materialnot secured to backing plate properly;¥ Excessive wheel bearing play;¥ Inspect brake hoses for ballooning (line lock at top of hose);¥ Excessive rotor runout;¥ Defective calipers causing the piston to retract too far into thebore; and¥ Excessive rust build-up between pad/shim and caliper housing. Pedal ishigh and Pedal is stilllow or spongy Pedal ishigh and Pedal is lowor spongy Pedal ishigh and Pedal is lowor spongy Pedal ishigh and Pedal is lowor spongy Pedal ishigh and Pedal is lowor spongy Pedal ishigh and Pedal is lowor spongy Pedal ishigh and 1. Reconnect secondarybrake line to master2. Bleed at fitting.3. Open fitting anddepress brake pedalone inch, tighten fitting. 1.3C: Secondary Circuit Good.1. Connect primary circuit brake line tomaster cylinder.2. Bleed line at fitting.3. Open fitting anddepress brake pedalone inch, tighten fitting. 1.3D: Air in Secondary Circuit Between Seals are bypassing internally in master. Replace master cylinder. See note.NOTE: If master cylinder has just beeninstalled, bench bleed unit again followingthe correct procedure and retest. Primary Circuit Good.If pedal is high and hard at thistime, the problem was probablya pocket of air that was removedduring test procedure. Removeline locks at wheels and checkpedal. If pedal is good, test drivevehicle. If still low, retest system. 1.3E: Air in Primary CircuitBetween Line Lock and Master1. Locate next component in primary circuit.2. Plug outlet of component andbleed fitting.3. Open fitting and depress Secondary Circuit Good.If pedal is high and hard at thistime, the problem was probablya pocket of air that was removedduring the test procedure.Reconnect primary line andbleed at fitting. If pedal is highand hard, remove line locks atwheels and check pedal. Ifpedal is good, test drive thevehicle. If pedal is still low, retest 1.3F: Air in Secondary CircuitBetween Line Lock andMaster Cylinder.1. Locate next component insecondary circuit.2. Plug outlet of componentand bleed at fitting.3. Open fitting and depressbrake pedal one inch, tighten Component tested is notsource of problem.1. Locate next componentin system and repeatprevious step.2. Repeat this procedureuntil faulty component is Component being tested iscause of pedal condition.1. Attempt to bleed 2. If bleeding does notchange pedal condition,replace component andretest system. Component tested is notsource of problem.1. Locate next componentin system and repeatprevious step.2. Repeat this procedureuntil faulty component is Component being tested iscause of pedal condition.1. Attempt to bleed 2. If bleeding does notchange pedal condition,replace component andretest system. , SPONGY Call us for all your brake caliper needs.(888) 740-0829Visit our website: http//www.ucx.comE-Mail: ucx@pobox.comFax: (216) 249-3396323 Eddy Road, Cleveland, Ohio 44108