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Fault Diagnosis

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					             Fault Diagnosis
                      DISC BRAKE PADS




• Ferodo Friction materials
• Components of the brake system
• Components of the hydraulic system

• Trouble shooting

   – Possible causes (Part 1)

   – Problem solving (Part 2)

• INSPECTION OF COMPONENTS
                  Friction materials
Disc pads.
   CERAMIC :-
   standard use

  PLATINUM :–
  premium use

  DS PERFORMANCE :–
  specialist
       Friction materials

Ceramic disc pads.
  Asbestos free

  Metal free

  Stable co-efficient
 of friction
       Friction materials
Platinum disc pads.
   Asbestos free

  Semi-metallic

  Stable co-efficient
 of friction
 The Brake System is a “Whole system”
     and all components must work in
      EQUILIBRIUM with each other

Light Duty Systems

  Hydraulic System

  Mechanical System

  Friction System

  Operator
           Hydraulic systems
              Inspection
Master Cylinders     Reservoir
                                           Piston

                                                Spring
Brake Pipes

Brake hoses
                     Master cylinder   Brake pipe
Calipers

Brake booster
                   Brake pedal
Brake Fluid
                                                    Slave cylinder
        Hydraulic systems
Master Cylinders :-

Sizes

Contamination
                Hydraulic systems


Brake Pipes:-

Age

Material

Mechanical valving
           Hydraulic systems.


Brake Hoses:-
Age

Type

Porosity
                Hydraulic systems

Calipers:-
Seals

Age

Replacement frequency

Porosity
                        Piston


                                 Seal
                                        Piston
                                        Dust boot
              Hydraulic systems
  Brake booster:-
•Brake fluid leaks     Vacuum pipe
                                     Vacuum valve


•Booster vacuum pipe
•Vacuum valve
•Check condition

                        Seal

                                               Diaphragm
                                Spring
            Hydraulic systems
BRAKE FLUID
 Check the Brake Fluid
  •Black
  •Clear
  •Muddy Brown
  •When was the brake fluid last
     CHANGED?
  •Boiling point of the Brake Fluid?
  •Has it been tested? yes/no
  •How was it tested?
    Light Duty Trouble Shooting

Category A - Audible


Category B - Physical


Category C - Performance


Category D - Aesthetic
Light Duty Trouble Shooting

   Category A   Audible.



• Squeal        High-pitched noise

• Graunching    Metal on metal grinding

• Rattle        Metallic rattle, clunking.

• Grinding      Scraping noise.
        Light Duty Trouble Shooting
CATEGORY “A” AUDIBLE.

  Complaint
  Squeal - High-pitched noise.
  • Possible causes
  • Dust.
  • Dirty Pistons and Calipers.
  • Wheel Bearings worn or badly adjusted.
  • Discs worn.
  • Suspension Rubbers Perished.
  • Changes from the front influencing
     performance at the rear
        Light Duty Trouble Shooting

CATEGORY “A” AUDIBLE
  Complaint
  Graunching - metal on
  metal grinding
   • Possible causes
   • Metal Pick-up
   • Slide pins burred or worn
Light Duty Trouble Shooting

CATEGORY “A” AUDIBLE
  Complaint
  Rattle - Metallic rattle,
  clunking
   • Possible causes
   • Pads not fitted correctly
   • Anti Rattle Plates Omitted
   • Anti Rattle Springs
        Omitted
        Bent
   • Inherent to Vehicle
Light Duty Trouble Shooting
CATEGORY “A” AUDIBLE
  Complaint
  Grinding - Heavy metal grinding, scraping noise
   • Possible causes
   • Disc Pads BACK TO FRONT
   • Friction material completely worn out
Light Duty Trouble Shooting


Category B              Physical.



 •   Lock-up     Brakes grab & Lock.

 •   Judder      Rhythmic, oscillating shudder,
                 also noisy.

 •   Snatching   Brakes grab & let go.
    Light Duty Trouble Shooting
Category “B” Physical.

 Complaint
 Lock-up - Brakes grab & lock-up,
  • Possible cause
  • Air in Hydraulic System.
  • Foreign objects.
  • Wrong co-efficient of friction.
  • Load sensor valve not working or not
    set-up.
  • Narrower Tyres fitted.
  • Suspension raised.
    Light Duty Trouble Shooting
Category “B” Physical

  Complaint
  Judder - Rhythmic, oscillating
  shudder, also noisy.
  • Possible causes
  • High spots on Discs
  • Caliper seizure
  • Slide Pins Bent
  • Discs Warped
      Light Duty Trouble Shooting
Category “B” Physical.

  Complaint
 Snatching - Brakes grab & let
 go.
  • Possible causes
  • Caliper action not smooth.
  • Brake fluid contaminated.
           Light Duty Trouble Shooting
     Category C Performance
•   Fade        Spongy feel to brake
                pedal, resulting in pedal
                fade.

•   Brake Fade - Inefficient stopping power.

•   Dead Pedal - Dead, non-progressive
                 feel to pedal.

•   Hesitation- Short delay before brakes take
         Light Duty Trouble Shooting
Category “C ” Performance.
  Complaint
  Fade - Spongy feel to pedal, resulting in
  pedal fade.
   •   Possible causes
   •   Hydraulic Blockage.
   •   Overloading.
   •   High Speed driving and short braking.
   •   Modified vehicle.
   •   Contaminated Brake Fluid.
        Light Duty Trouble Shooting
Category “C ” Performance.
 Complaint
 Brake Fade - Insufficient stopping power.
  • Possible causes
  • Contaminated Brake Fluid.
  • Sticking/Seized Calipers (Overheating).
  • Incorrect friction material fitted
    Light Duty Trouble Shooting


Category “C ”
 Performance.
 Complaint
 Dead Pedal - Dead non -
 progressive feel to pedal.
  • Possible causes
  • Caliper Seized.
  • Master Cylinder Blocked.
  • Brake Pipes Blocked.
  • Backing Plates Bent.
    Light duty trouble shooting
Category “C” Performance
    Complaint
    Hesitation – a short delay before the
    brakes take
•   Possible causes
•   Air in hydraulic system.
•   Insecure brake mountings.
•   Pedal free play excessive.
•   Firewall movement due to
    degeneration
   Light Duty Trouble Shooting

Category D          Aesthetic

Dust    Due to wear – disc or pads

Smell   New pads - bedding in

Smoke   After heavy braking
        Light Duty Trouble Shooting

Category “D ” Aesthetic


  Complaint
  Dust - Dust formed due to wear
  of disc & friction material.
   • Possible causes
   • Inherent in braking.
   • Lesser quality materials.
          Light Duty Trouble Shooting
Category “D ” Aesthetic
Complaint
  Smell - Usually during bedding-in or
  heavy braking.
   • Possible causes
   • Short lived 300 Km.
   • During descents down long hills
     with capacity loads.
   • After emergency stopping from
     speed.
      Light Duty Trouble Shooting
Category “D ” Aesthetic
 Complaint
 Smoke - From the wheel arches.
  • Possible causes
  • After heavy braking the
    material remains hot for a
    period.
         Light Duty Trouble Shooting
Trouble Shooting
  Observations
 Selection of the RIGHT TOOLS

  •   Avoid damage to the

      COMPONENTS of the system.

  •   Correct SIZE tools.

  •   No EXCESSIVE force.

  •   Pride of WORKMANSHIP.
      Light Duty Trouble Shooting
Trouble Shooting Observations.
 Removal of the DISC PADS.

  •   Loosening the CALIPER,

        Were the mounting points OK?
                                               Caliper mounting
        Did it appear to be in good working    points


        condition?

  •   Pushing the PISTONS back,

        Did the pistons push back easily,

        or were they stiff?

        Was the Bleed Nipple loosened before

                     pushing the pistons back?
        Light Duty Trouble Shooting
Trouble Shooting Observations
 Inspection of the DISC PADS

  •   Were the Disc Pads the CORRECT
      PART Number?

  •   Have the Disc pads been MODIFIED?

  •   Are the Disc Pads CRACKED?

  •   Are the Backing Plates BENT?

  •   How thick is the FRICTION MATERIAL?

  •   Was one Disc Pad more WORN than the
      Other (Inner/Outer)?
        Light Duty Trouble Shooting
Trouble Shooting Observations
 Inspection of the DISCS
  •   Are the discs
         VENTILATED or SOLID?
  •   Are the Discs
         CRACKED or GROOVED?
  •   Are the Discs Blued
         One Side or Both
  •   Are there signs of METAL PICK-UP?
  •   Are there HIGH SPOTS?
  •   Is the Disc WARPED?
  •   Do the discs conform to the legislated
      specification?
        Light Duty Trouble Shooting
Trouble Shooting Observations
 Inspection of the CALIPERS
  •   What TYPE of Caliper is it?
  •   Are the SLIDE PINS in good condition?
  •   Does the PISTON move freely in the
      Caliper?
  •   Are there CRACKS on the piston or the
      Casting?
  •   Are the RETAINING BOLT HEADS
      damaged?
  •   Are the MOUNTING POINTS
       solid?
           Light Duty Trouble Shooting
Trouble Shooting Observations
    Inspection of the DUST SEALS

    •   Slide Pin Seals

    •   Pistons Seals

•   Bleed Nipple Covers

        In Place?

        Torn?

        Cracked ?

        Melted?
        Light Duty Trouble Shooting
Trouble Shooting Observations
 Inspection of the vehicle
 MODIFICATIONS TO THE VEHICLE.
  •   Are the CALIPERS the specified ones?
  •   Has the MOTOR been changed?
         V8 Tow Truck.
  •   Has the BODY been changed?
         Cash in Transit Vans.
  •   Are there WIDER TYRES fitted?
  •   Are there NARROWER TYRES fitted?
  •   Has the SUSPENSION been modified?
             Lowered or Raised.
        Light Duty Trouble Shooting
Problem Solving:
  Observations
Foreign objects.
   • Chips and/or Gouges on the
      friction material.
   • Discs Badly scoured.
   • Objects picked-up by tyres and
      thrown into the caliper.
      ACTION:
Clean out caliper and replace brake
   pads.
      Light Duty Trouble Shooting
Problem Solving:
 Observations
  Discs Warped.
  • Pedal Jump.
  • Judder.
  • Steering Pull.
  • Poorly Skimmed.
  • Over Heated.
      Actions:
Replace the Discs and the pads
  as well as the Brake Fluid.
        Light Duty Trouble Shooting
Problem Solving:
  Observations
  Slide Pins Bent /Worn.
   • Caliper Seizure.
   • Sticky Caliper Movement.
   • Judder or Squeal.
   • Steering Pull.
   • Not correctly tightened.
   • Forced at some stage.
       Actions:
Remove and replace the pins and seals.
Check for other damage.
      Light Duty Trouble Shooting
Problem Solving:
  Observations
   • One pad worn
   • High spots
   • Steering pull
   • Slide pins coated with old lubricant
      & brake dust
   • Dust covers worn or melted
          ACTIONS
Overhaul Caliper.
Replace all Seals and Brake Fluid.
Lubricate slide pins with CV grease.
       Light Duty Trouble Shooting

Problem Solving:
  Observation
   Disc pads back to front
   •  Graunching
   • Grinding
       Action:
Training required
Replace pads and fit correctly
  Light Duty Trouble Shooting
Problem Solving:
  Observations
 Pistons Seized
  • High pad wear rate
  • Disc warp
  • Disc discoloration
  • Brake fade
  • Calipers never cleaned or
    overhauled
  • Dust covers torn, melted or
    missing
  • Poor maintenance
 Actions:     Overhaul Calipers
              Replace the seals and
              the brake fluid
    Light Duty Trouble Shooting

Problem Solving: Observations
   and Consequences
   Dust Covers Torn
   •   Piston seizure
   •   Brake fluid leak
   •   Caliper action not smooth
   •   Brake fluid contaminated
   •   Dust covers aged and
       perished
   •   Poor fitting procedures
   • Foreign objects
      Actions:
Remove and replace
      Light Duty Trouble Shooting

Problem Solving:
 Observations
  Hydraulic Hoses Leaking
   • Brake fade or Failure
   • Excessive Pedal Travel
   • Vibration or Scuffing
   • Incorrectly tightened
   • Cuts from foreign matter
       Actions:
Replace completely
        Light Duty Trouble Shooting

Problem Solving:
  Observations
  Metal Pick-up
   • Discs badly scored
   • Pads show traces of metal
     splinters (check with magnet)
   • Metallurgical reaction of disc
     material to disc pads
         Actions:
Replace Discs and Disc Pads.
Light Duty Trouble Shooting
Problem Solving:
  Observations
       High Spots on dics
  •   Points of discoloration at a
      radius usually equally
      spaced
  •   Calipers not functioning
      properly
  •   Discs not skimmed correctly
      Actions:
 Check Calipers
 Re-skim Discs or replace Discs
      Light Duty Trouble Shooting
Problem Solving:
  Observations
 Discs Over Skimmed (too thin).
  • Warping.
  • Cracking.
  • Disintegration.
  • Lack of observation by skimmer.
  • Poor vehicle management.
    Action:
     Replace Discs.
       Light Duty Trouble Shooting
Problem Solving:
 Observations
  Pads not fitted correctly.
   • Backing plates bent.
   • Pads badly worn (tapered).
   • Lack of training.
   • Poor workmanship.
      Actions:
Training required
Replace disc pads correctly.
       Light duty trouble shooting

Problem solving: Observation
    Cracked pads
•   Pads flexing
•   Pads not free to move
•   Piston bent in back plate
•   Actions:
•   Replace pad set
        Light Duty Trouble Shooting

Problem Solving:
  Observations
    Incorrect pads fitted
    •  Damaged pads
    •  Friction material lose
     from back plate
         Actions:
•   Training required
•   Replace disc pads
    correctly
       Light Duty Trouble Shooting


Problem Solving:
  Observations
  Pads surface glazed.
  • High temperature at
    short durations
      Actions:
Correct by normal use
      Light Duty Trouble Shooting
Problem Solving:
  Observations
    Denaturing.
    • Whitish outer edge.
      (denaturing)
•   Excessive temperature due to
    intensive use or dragging
        Actions:
    If minor damage pads can be
    re-used but recommend
    replacement

				
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