Brake ServiceBrake Service

Chapter 52Chapter 52

Page 732Page 732

Diagnosis is KeyDiagnosis is Key

This will make or “brake” you as a technician.This will make or “brake” you as a technician. This is really no laughing matter because if This is really no laughing matter because if

we don’t find the problem, mis-diagnose, or we don’t find the problem, mis-diagnose, or don’t properly repair a brake problem it could don’t properly repair a brake problem it could lead to our harm and/or (on a test drive) the lead to our harm and/or (on a test drive) the customers life as well if the problem is not customers life as well if the problem is not found on a test drive. (we don’t test drive found on a test drive. (we don’t test drive after most repairs here at SPHS– it may come after most repairs here at SPHS– it may come up and get us someday; so do it right and let up and get us someday; so do it right and let me look at it before you turn the car loose.)me look at it before you turn the car loose.)

Brake Pedal CheckBrake Pedal Check

•Should not be any pulsation in the pedal•Put light pressure on the pedal (engine off) if the pedal sinks, it indicates an internal leak in the master cylinder•Should be about two inches of reserve pedal at the bottom of the brake travel

•Make sure the car doesn’t pull left or right dip the front or rear – might indicate a brake problem•Should be about an inch of free pedal at the top

Master Cylinder Master Cylinder InspectionInspection

Hold pedal down with light pressure for up to a Hold pedal down with light pressure for up to a minute, if the pedal sinks and there is no external minute, if the pedal sinks and there is no external leakage of the system; it indicates an internal leak leakage of the system; it indicates an internal leak of the master cylinderof the master cylinder

Check for roughly equal fluid levels in the reservoir; Check for roughly equal fluid levels in the reservoir; if one the front brake chamber is lower it may if one the front brake chamber is lower it may indicate worn brake pads ( front brakes do more indicate worn brake pads ( front brakes do more work) or one of the piston areas are leaking over work) or one of the piston areas are leaking over and overflowing the other chamber.and overflowing the other chamber.

Replenishing orInlet port

Compensating PortCheck Fluid level

Rear seal CheckRear seal Check

ContinuedContinued Check the compensating portsCheck the compensating ports—( have —( have

a partner press the brake pedal down while the a partner press the brake pedal down while the cover of the reservoir is off and you should see a cover of the reservoir is off and you should see a small surge coming up in each chamber; if there small surge coming up in each chamber; if there is a heavy surge, there is air in the system)is a heavy surge, there is air in the system)

Brake dragBrake drag– – if the compensator ports areif the compensator ports are blocked or the brakes pedal is adjusted to tightly, blocked or the brakes pedal is adjusted to tightly, the brakes will be applied all the time. the brakes will be applied all the time. (try rolling the vehicle by hand– it should roll (try rolling the vehicle by hand– it should roll

easilyeasily.. Isolating an air-in-system problemIsolating an air-in-system problem– –

same as compensating port test; but; pump the same as compensating port test; but; pump the pedal 10 times and hold the last pump– then pedal 10 times and hold the last pump– then release– note the chamber with the high surge.release– note the chamber with the high surge.

Power Brake CheckPower Brake Check

With the engine off, pump the pedal With the engine off, pump the pedal several times as you do you should several times as you do you should hear a rushing sound—this checks hear a rushing sound—this checks for a hole in the booster diaphragm for a hole in the booster diaphragm which would render it useless.which would render it useless.

With pressure on the pedal, start the With pressure on the pedal, start the engine and the pedal should sink engine and the pedal should sink about an inch.—If yes, it’s a good about an inch.—If yes, it’s a good booster.booster.

Brake Switch TestBrake Switch Test

Push the pedal and have a partner check Push the pedal and have a partner check for light operationfor light operation * if all lights don’t work check the fuse first * if all lights don’t work check the fuse first

before changing out the switchbefore changing out the switch The switch has two wires—one in (12 volts) The switch has two wires—one in (12 volts)

and one out (should also be 12 volts is and one out (should also be 12 volts is switch is o.k.)switch is o.k.)

Road Test or Customer Road Test or Customer Complaint DiagnosisComplaint Diagnosis

Pedal pulsation— Drums out of round, Pedal pulsation— Drums out of round, rotors warped. –might need resurfacing or rotors warped. –might need resurfacing or replacement.replacement.

Grab– grease or oil on the linings, wrong or Grab– grease or oil on the linings, wrong or improperly installed pads.– clean and fix improperly installed pads.– clean and fix oil/grease problem.oil/grease problem.

Pull– oil on one set of pads (on one side of Pull– oil on one set of pads (on one side of vehicle), frozen caliper, blocked hose, loose vehicle), frozen caliper, blocked hose, loose brake parts.-various repairs needed. brake parts.-various repairs needed.

Brake Pull cont.Brake Pull cont.

If the vehicle pulls to one side while If the vehicle pulls to one side while braking– check for a brake not braking– check for a brake not working on the opposite side of the working on the opposite side of the pull.pull.

Don’t forget, worn wheel bearings, Don’t forget, worn wheel bearings, bad suspension parts, and chassis bad suspension parts, and chassis part all could create a brake pull.part all could create a brake pull.

Brake System ChecksBrake System Checks

Disc Brakes Disk Pad Thickness Comparison

Drum Brakes Drum Brake Lining Thickness Comparison

Disk Brake CheckDisk Brake Check

Items to Check (disk)Items to Check (disk)

Check Lines forChecks, Chaffs,and Bulging

Check the caliper and mount for Tightness– check for leakage

Check the condition of the lug studs---- and axle nut for tightness

Check the rotorFor warpage, cracks,and roughness

Check bearingsFor looseness

Use Dial Indicator Use Dial Indicator

Disc Brake R & RDisc Brake R & R

Measure Rotor Thickness Measure Rotor Thickness With a MicrometerWith a Micrometer

Rotor Micrometer

Fluid ServiceFluid Service Check fluid with a multimeter--- no more Check fluid with a multimeter--- no more

than .3 volts— replace fluidthan .3 volts— replace fluid Check for dirty or clouded fluid– should be Check for dirty or clouded fluid– should be

clear **DOT 5 has a purple dye added to clear **DOT 5 has a purple dye added to identify and caution you not to mix DOT 5 identify and caution you not to mix DOT 5 with the others.with the others.

BleedingBleeding

BleedingBleeding

Types of bleedingTypes of bleeding Manual Manual PressurePressure VacuumVacuum GravityGravity

Try to catch the fluid.Remember it is harsh on paint.

Use dielectric grease for a good seal

Master Cylinder ServiceMaster Cylinder Service

Most of this is Most of this is just replacing the just replacing the cylinder.cylinder. You may have to You may have to

change out the change out the reservoir when reservoir when you get a new you get a new cylinder.cylinder.

Take care not to Take care not to cross-thread the cross-thread the lines. Always start lines. Always start by hand.by hand.

Master Cylinder ServiceMaster Cylinder Service

Before installation the master cylinder Before installation the master cylinder needs to be bench bled. (you can use the needs to be bench bled. (you can use the master cylinder installed method seen master cylinder installed method seen below)below)

These adapters come with most new cylindersPump pedal until all air is purged

Drum Brake CheckDrum Brake Check

Items to Check (drum)Items to Check (drum)

Check LiningThickness

All springs for “spring”

Check anchoring clips

Check WheelCylinder forLeakage

Drum PartsDrum Parts

Hardware Backing plate

Drum

Wheel Cylinder

Adjusting Screw

Wheel CylindersWheel Cylinders Replacing this is more common than Replacing this is more common than

rebuilding themrebuilding them The bleeder is usually frozen– take some The bleeder is usually frozen– take some

penetrating oil and give it time to work, use a penetrating oil and give it time to work, use a six point socket and try to remove. You might six point socket and try to remove. You might get it; out 50/50 shot at it.get it; out 50/50 shot at it.

Same goes for the lines.Same goes for the lines. It is held to the backing It is held to the backing plate with two bolts fromplate with two bolts from the back side.the back side. Any leaks=ReplacementAny leaks=Replacement

Drum Brake R & RDrum Brake R & R

Caliper ServiceCaliper Service It is more common to replace calipers thanIt is more common to replace calipers than

to rebuild.to rebuild. The bleeder is usually frozen– take some The bleeder is usually frozen– take some

penetrating oil and give it time to work, use penetrating oil and give it time to work, use a six point socket and try to remove. You a six point socket and try to remove. You might get it; out 50/50 shot at it.might get it; out 50/50 shot at it.

Same goes for the lines.Same goes for the lines. Copper sealing rings at the line must Copper sealing rings at the line must

be replaced each time the line is off be replaced each time the line is off

( 2 of them per)( 2 of them per) Any leakage= ReplacementAny leakage= Replacement

Measuring the Rotor or Measuring the Rotor or Drum Drum

This is important to do right because This is important to do right because it will determine if these parts can be it will determine if these parts can be resurfaced or if they need resurfaced or if they need replacementreplacement

Remember it is illegal not to mention Remember it is illegal not to mention dangerous to knowingly ignore these dangerous to knowingly ignore these readings. readings.

Resurfacing Rotors and Resurfacing Rotors and DrumsDrums

Follow the directions next to the brake Follow the directions next to the brake lathe only if the rotor/drum has 25 lathe only if the rotor/drum has 25 thousandths to work with.thousandths to work with. Example 10.030 Max (drum specification)Example 10.030 Max (drum specification) Your measurement 10.005Your measurement 10.005 Example .850 Min (rotor spec)Example .850 Min (rotor spec) Your Measurement .880Your Measurement .880

Don’t forget to crosshatch a finishDon’t forget to crosshatch a finish

Adjusting Parking Brake Adjusting Parking Brake CableCable

Adjusting Parking Brake Adjusting Parking Brake LeverLever

Adjusting Parking BrakeAdjusting Parking Brake

Vacuum Booster ServiceVacuum Booster Service The vacuum hose going into the front The vacuum hose going into the front

chamber needs to be in good shape.chamber needs to be in good shape. Gently pry the check valve out and a rush Gently pry the check valve out and a rush

of air into the booster should be heard.of air into the booster should be heard. The check valve will need to be replaced if The check valve will need to be replaced if

the brake work accordingly to the engine the brake work accordingly to the engine RPMs.RPMs.

Check to see if the rear chamber of the Check to see if the rear chamber of the master cylinder is up to level- the booster’s master cylinder is up to level- the booster’s seal might be bad and drawing fluid into seal might be bad and drawing fluid into booster. booster.

Brake AssignmentsBrake Assignments

Inspection of system and componentsInspection of system and components Turn rotors and drums, measure run-Turn rotors and drums, measure run-

out, diameter, thickness of pads discs out, diameter, thickness of pads discs and rotors.and rotors.

Adjust parking brakeAdjust parking brake Wheel bearing work (possibly) Wheel bearing work (possibly) Cleaning brakesCleaning brakes BleedingBleeding Component R+RComponent R+R

Your Job.Your Job.

Complete chapter Questions 1-10 Complete chapter Questions 1-10 (review) and 1-10 (ASE-style). Page 760(review) and 1-10 (ASE-style). Page 760

Write on a separate paper and write Write on a separate paper and write out the complete question and your out the complete question and your answer. ( do not write the other answer answer. ( do not write the other answer options). options).

Complete the chapter worksheet (I will Complete the chapter worksheet (I will give it out). You may write on it. give it out). You may write on it.

File all items in your note book.File all items in your note book. Notebooks will be graded in the future.Notebooks will be graded in the future.