© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Publisher The Goodheart-Willcox Co., Inc. Tinley Park, Illinois by Russell Krick

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Vibration  Shows up as a chatter, pulsation, or shake in the brake pedal or steering wheel  Occurs only when the brakes are applied  Front brake problems may be felt mostly in the steering wheel  Pulsation in the brake pedal may be caused by brake problems at any wheel

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Vibration  Possible causes:  warped disc  out-of-round brake drum  hard spots on the disc or drum

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Grabbing Brakes  Brakes apply too quickly, even with light brake pedal application  Possible causes:  malfunctioning brake booster  brake fluid or grease on the linings  worn brake linings  faulty metering valve  mechanical problem in the wheel brake assembly

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Pulling Brakes  The vehicle veers to the right or left when the brakes are applied  Possible causes:  seized caliper or wheel cylinder piston  grease- or fluid-coated lining  leaking cylinder  faulty automatic adjuster  brake lining dust in a drum brake assembly

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Spongy Brake Pedal  The brakes will apply, but the pedal does not feel solid  Possible causes:  air in the brake system  faulty residual check valve in the master cylinder  maladjusted brake shoes

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Dropping Brake Pedal  The pedal slowly moves all the way to the floor when steady pressure is applied to it  Pumping usually restores pedal height momentarily  Possible causes:  internal leak in the master cylinder  external fluid leak in any component

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Dragging Brakes  The brakes remain partially applied when the brake pedal is released  To detect dragging brakes, carefully feel each brake assembly  dragging brakes will be abnormally hot

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Dragging Brakes  Possible causes:  seized wheel cylinder pistons or parking brake cables  overadjusted parking brake or master cylinder push rod  weak return springs  brake fluid contamination  master cylinder problems

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Braking Noise  Noises include grinding sounds, squeaks, or rattles  Metal-on-metal grinding sound when braking  caused by worn brake linings

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Braking Noise  Squeak when braking  caused by glazed, or hardened, brake linings; a dry brake drum backing plate; or a wear indicator rubbing on the rotor  Rattles  caused by a missing anti-rattle clip or loose parts

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Checking Brake Pedal Action  Apply the brake pedal and compare the movement to specifications  Brake pedal application specs:  pedal height  pedal free play  pedal reserve distance

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Brake Pedal Measurements

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Using a yardstick to measure the distance from the steering wheel to the brake pedal Brake Pedal Measurements

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Inspect the brake booster and the vacuum hose  hoses may collapse or harden  To test the booster, pump the brake pedal to remove any vacuum  Apply the brake and start the engine  the pedal should drop slightly as engine manifold vacuum develops

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  A faulty master cylinder may leak fluid past the rear piston or leak internally  Inspect for external leakage where the master cylinder mounts to the booster or cowl  Internal leakage will cause the pedal to slowly sink to the floor when pressure is applied

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Master Cylinder Removal  Disconnect the brake lines using a line wrench  Unbolt the master cylinder from the booster or cowl  On a vehicle without a power-assist booster, disconnect the push rod from the brake pedal assembly

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Master Cylinder Rebuild  Following the service manual procedures, drain the fluid and disassemble the unit  Honing may be used to remove minor corrosion or pits from the cylinder  surface must be in perfect condition  Measure piston-to-cylinder clearance  Inspect each component and replace all cups and seals

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Clean and lubricate the components with brake fluid and reassemble the unit Master Cylinder Rebuild

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Bench Bleeding Removes air from inside the master cylinder

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Installing a Master Cylinder  Bolt the master cylinder to the firewall or booster  Check the adjustment of the push rod if specified  Install the brake lines with the fittings lightly tightened

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Installing a Master Cylinder  Bleed the air from the fittings  Tighten the fittings  Fill the reservoir with fluid  Check brake pedal feel and road test the vehicle

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Air in the brake system will compress, causing a spongy brake pedal  Bleeding involves the use of fluid pressure to force air out of the brake system bleeder screws  Two methods are used:  manual bleeding  pressure bleeding

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Manual Bleeding  Attach one end of a hose to a bleeder screw and place the other end in a jar containing brake fluid  Have another technician apply light foot pressure on the brake pedal  Open the bleeder screw while watching for air bubbles flowing from the hose

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Manual Bleeding  Close the bleeder screw  Have your helper release the brake pedal  Repeat the steps until the flow from the hose is clear and free of bubbles  Perform the operation on all the brake assemblies, starting farthest from the master cylinder

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Manual Bleeding

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Pressure Bleeding Uses a pressure bleeder tank, which contains brake fluid under pressure

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Pressure Bleeding  Fill the tank with fluid  Charge the tank with 10–15 psi (69–103 kPa) of air pressure  Fill the master cylinder with fluid  Install the adapter and hose on the master cylinder  Open the valve in the hose

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only  Attach one end of a hose to a bleeder screw and place the other end in a jar containing brake fluid  Open the screw until the fluid entering the jar is clear of bubbles Pressure Bleeding

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Pressure Bleeding Repeat the steps on the other wheel brake assemblies

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Flushing a Brake System  Extends the life of the brake system components  Done by pressure bleeding all the old fluid out of the system  Removes contamination, such as dirt, rust, corrosion, oil, or moisture  Bleed each wheel brake assembly until clean fluid flows from the bleeder screw

© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only Tools and Procedures A brake vacuum is being used to prevent inhalation of brake lining dust