basic brakes

Download Basic Brakes

Post on 31-Dec-2015

15 views

Category:

Documents

0 download

Embed Size (px)

DESCRIPTION

Basic Brakes. Split systems/dual master cylinders. Used exclusively since 1960s Most use front/rear split Some use diagonal split. Brake Fluid. Fluid ruins paint!!! Use DOT 3 in virtually all cars Never ever mix with petroleum based liquids - PowerPoint PPT Presentation

TRANSCRIPT

  • Basic Brakes

  • Split systems/dual master cylindersUsed exclusively since 1960sMost use front/rear splitSome use diagonal split

  • Brake FluidFluid ruins paint!!!Use DOT 3 in virtually all carsNever ever mix with petroleum based liquidsWhen cleaning brake parts use only brakeclean, clean brake fluid, or denatured alcoholVery hygroscopicSome recommending flushing intervals

  • Master cylinderPrimary piston is acted on by pushrodSecondary piston is acted on by hydraulic pressureEach piston will have its own:Compensating portVent (relief) portReturn springReservoir

  • Master cylinder diagnosisUsually fails with one cup bypassingLow or no fluid pressure from one side of cylinderLow pedal with brake light coming onMoisture or petroleum in cylinder will destroy/swell cups

  • Master cylinder repairsRebuilding rare todayMost new are rebuilt MUST be bench bled before installationIf done completely system bleeding will not be necessary

  • Power boostersCan be vacuum or hydraulic boostedVacuum uses engine vacuum to assist pedal travelHydraulic shares power steering pressure off of pump to assist pedalBoth have fail safe if booster failsFail-safe will require increased pedal effort

  • Vacuum booster testingPedal will fall away when engine startedWill store vacuum for two or three applicationsIf vacuum leaks off possibly check valve leakage or internal leakageBrake fluid in booster indicates failed master cylinder and both must be replaced

  • Brake hoses and linesSteel lines are double wallUse special double flare ISO flare steel or brass fittingsNever use single flare or compression fittingsHosesUsually double lined hosesLines on hose body should not twist when installed

  • Brake hoses and lines problemsHoses can balloon only under pressure causing spongy brakesInner wall can block off flow/pressureMetal lines can rust from inside out

  • Common hydraulic valvesPressure differential valveMetering valve Proportioning valve

  • Drum brake Duo-servo vs. non-servoShoesPrimary / secondaryRiveted vs. bondedAsbestos still aroundDrumsUsually cast ironMust carry heat away

  • Drum brake serviceDrum removalCan be rusted around center of drumImports may have threaded removal holesMay need to adjust down shoesIf shoes are wet with brake fluid, oil, grease shoes must be replacedDrums should be resurfacedAll dust MUST be wetted down or vacuumed away

  • Drum brake serviceShoes should be replaced one side at a time for comparison purposesUsually remove return springs first, hold downs secondAny weak or stretched spring needs new hardware kit

  • Drum brake serviceAdjuster should be cleaned and lubricatedBacking plate pads need lubricationRoll back dust boots for inspectionAny grease or brake fluid on shoes should be cleaned off before installation

  • Drum brake problemsGrabbingSquealing when appliedFadingPulsating pedalMust isolate front or rearSnapping or clicking noiseGrinding when appliedLow brake pedalLocked up on very cold days

  • Disc brakeTwo categoriesFixedMovingCalipers containing one or two pistonsFloating caliper and sliding caliper must move freely Rotors usually cast iron - can be vented or solidPads often will have wear indicators

  • Disc brake serviceMost require R&R of calipersSlides and pins must be cleaned and lubedSome pads have anti-rattle plates or require anti-squeak adhesive to back of pads or will have retaining tabsAs pads wear fluid level will dropPiston must be bottomed in bore DO NOT allow caliper to hang by hose

  • Disc brake problemsPulsating brakes very commonBinding caliper piston or slides

  • Drum/rotor resurfaceDemo on car

  • Brake bleedingDemo on car