DISC AND DRUM BRAKETROUBLE SHOOTING 2002 Federal-Mogul Corporation
DISC AND DRUM BRAKE TROUBLE SHOOTING1. EXCESSIVE PEDAL TRAVEL2. GRABBING OR UNEVEN BRAKING ACTION3. FRONT DISC BRAKES VERY SENSITIVE TO LIGHT BRAKEAPPLICATION4. EXCESSIVE PEDAL EFFORT5. RATTLES OR BRAKE SQUEAL6. BRAKE CHATTER, ROUGHNESS OR PULSATION7. PREMATURE REAR WHEEL LOCK-UP UNDER HARD BRAKEAPPLICATIONS8. SCRAPING9. DRAGGING BRAKES10. EXCESSIVELY HOT BRAKES AND FAILURE TO RELEASE11. BRAKE PEDAL CAN BE DEPRESSED WITHOUT BRAKING EFFECT12. BRAKE SYSTEM WARNING LIGHT DOES NOT TURN ON13. BRAKE SYSTEM WARNING LIGHT DOES NOT TURN OFF 2002 Federal-Mogul Corporation
1. EXCESSIVE PEDAL TRAVELPOSSIBLE PROBLEMPartial hydraulic system failure with dualhydraulic system.Low fluid level in reservoir.Incorrect master cylinder push rod adjustment.Air in hydraulic system.Rear brake not adjusting properly.Bent lining pad.Loose caliper mounting.Loose wheel bearing.Excessive lateral run-out of rotor.Weak or expanding brake hoses.CORRECTIONCheck front and rear system for failure andrepair. Fill and bleed system.Check for leak, repair, fill reservoir. Bleedsystem if necessary.Adjust push rod.Bleed system and refill master cylinder.Repair self-adjusting system and adjust brakes.Recondition caliper.**Replace hardware on single piston caliper.Torque mounting bolts to specifications.Adjust to specifications.Check run-out with dial indicator. Resurface orreplace rotor.Replace brake hose. Bleed system.2. GRABBING OR UNEVEN BRAKING ACTIONPOSSIBLE PROBLEMFront end out of alignment.Incorrect tire pressure.Unmatched tires.Restriction in hydraulic system.Loose caliper mounting.Wrong or damaged lining pad.Malfunctioning metering or proportioning valve.Power brake unit defective.Malfunctioning caliper assembly.Malfunctioning rear brakes.CORRECTIONCheck alignment. Replace worn parts.Realign front end.Inflate tires to recommended pressures.Tires with approximately the same amount oftread should be used on the same axle. Tiresshould be of the same type of construction.Check hoses and lines for damage. Replaceas necessary.Replace hardware on single piston caliper.Torque mounting bolts to specification.Recondition caliper.*Replace metering or proportioning valve.Repair or replace power brake unit.Recondition caliper.* Flush hydraulic systemwith brake fluid if seals are swollen.Check self-adjusting system and brake springs.Repair as necessary.3. FRONT DISC BRAKES VERY SENSITIVE TO LIGHT BRAKE APPLICATIONPOSSIBLE PROBLEMMetering valve malfunctioning.*CORRECTIONReplace metering valve and bleed system.RECONDITIONED CALIPERS: REPLACE ALL LINING PADS, HYDRAULIC PARTS. CLEANCALIPER BORE AND PISTONS ON BOTH CALIPERS. 2002 Federal-Mogul Corporation
4. EXCESSIVE PEDAL EFFORTPOSSIBLE PROBLEMCORRECTIONPower brake malfunction.Check power brake and repair if necessary.Partial hydraulic system failure with dualCheck front and rear system for failure andhydraulic system.repair.Lining worn beyond specification.Recondition calipers.**Sticking or frozen pistons in caliper.Recondition calipers.*Lining contaminated with grease, oil or brakeRecondition calipers.*fluid.Brake fade due to poor quality or incorrectReplace lining pads on both calipers.lining.NOTE: Due to the nature of the disc brake a squeal may be considered normal if and when itoccurs occasionally. A constant squeal indicates a possible problem in the brake.5. RATTLES OR BRAKE SQUEALPOSSIBLE PROBLEMLoose caliper mounting.Brake shoe anti-rattle spring weak or missing.Excessive shoe to caliper or shoe to pistonclearance.Poor quality lining.Rust.Worn hardware.CORRECTIONReplace hardware on single piston caliper.Torque mounting bolts to specifications.Replace anti-rattle springs.Recondition calipers.*Replace pads- use insulator type.Clean caliper- lube with high temp. grease.Recondition calipers.*6. BRAKE CHATTER, ROUGHNESS OR PULSATIONPOSSIBLE PROBLEMLoose wheel bearings.Front end out of alignment.Rear drums out of round.Lining contaminated with grease, oil or brakefluid.Excessive lateral run-out of rotor.Rotor excessively out of parallel.CORRECTIONAdjust wheel bearings to specifications.Check alignment. Replace worn parts.Realign front end.Resurface or replace rear drums.Recondition calipers.*Check run-out with dial indicator. Resurface orreplace rotor.Check rotor and resurface or replace.7. PREMATURE REAR WHEEL LOCK-UP UNDER HARD BRAKE APPLICATIONSPOSSIBLE PROBLEMProportioning valve malfunctioning.CORRECTIONReplace proportioning valve and bleed system.8. SCRAPING*RECONDITIONED CALIPERS: REPLACE ALL LINING PADS, HYDRAULIC PARTS. CLEANCALIPER BORE AND PISTONS ON BOTH CALIPERS. 2002 Federal-Mogul Corporation
POSSIBLE PROBLEMLoose wheel bearings.Rotor rubbing caliper housing or splash shield.Loose caliper mounting.Broken return springs on drum brakes.CORRECTIONAdjust to specifications.Check for rust or mud build-up on caliper orsplash shield next to rotor. Check for bentsplash shield.Replace hardware on single piston caliper.Torque mounting bolts to specifications.Replace return springs in axle set.9. DRAGGING BRAKESPOSSIBLE PROBLEMMaster cylinder pistons not returning correctly.Check valve installed in outlet to front discbrakes.Metering valve incorrectly installed.Incorrect parking brake adjustment or bindingparking brake cable.Restriction in hydraulic system.CORRECTIONWith reservoir cover off, check for fluid spurt atbypass hole, as pedal is depressed. Adjustpush rod if necessary or recondition mastercylinder.Check outlet hole and remove check valve ifline is connected to disc brake caliper.Port marked “inlet” goes to master cylinder.Port marked “outlet” goes to disc calipers.Correct binding cable if necessary and adjustto specifications.Check hoses and lines for damage. Replaceas necessary.10. EXCESSIVELY HOT BRAKES AND FAILURE TO RELEASEPOSSIBLE PROBLEMBroken brake return springs on drum brakes.Frozen or sticking caliper pistons.Driver’s foot riding brake pedal.Master cylinder or power brake malfunction.Sticking or binding pedal linkage.CORRECTIONReplace return springs in axle sets.Recondition calipers.**Instruct driver not to rest foot on pedal.Repair or replace master cylinder or powerbrake unit.Free up and lubricate linkage.11. BRAKE PEDAL CAN BE DEPRESSED WITHOUT BRAKING EFFECTPOSSIBLE PROBLEMNo fluid in master cylinder reservoir.Air in hydraulic system.Rear brakes out of alignment.Leaking wheel cylinders.Internal leak in master cylinder.Leaking caliper seals.CORRECTIONCheck for leak and correct. Fill master cylinderand bleed system.Bleed system and fill master cylinder.Check and repair self-adjusting system. Adjustrear brakes.Recondition or replace wheel cylinder.Recondition or replace master cylinder.Recondition calipers*.*12. BRAKE SYSTEM WARNING LIGHT DOES NOT TURN ON*RECONDITIONED CALIPERS: REPLACE ALL LINING PADS, HYDRAULIC PARTS. CLEANCALIPER BORE AND PISTONS ON BOTH CALIPERS.*RECONDITIONED CALIPERS: REPLACE ALL LINING PADS, HYDRAULIC PARTS. CLEANCALIPER BORE AND PISTONS ON BOTH CALIPERS. 2002 Federal-Mogul Corporation
POSSIBLE PROBLEMBulb burned out.Warning switch has open circuit.Damaged warning light switch.CORRECTIONReplace bulb.Check circuit and repair.Replace switch.13. BRAKE SYSTEM WARNING LIGHT DOES NOT TURN OFFPOSSIBLE PROBLEMOne section dual brake system inoperative.Differential pressure valve not centered.Grounded wire to warning light switch.Damaged warning light switch. 2002 Federal-Mogul CorporationCORRECTIONCheck for leaks and repair.Center valve.Correct grounded wire.Replace switch.
STOP AND THINK!IS IT NECESSARY TO REPLACE HARDWARE AND HYDRAULIC PARTS?CONSIDER THESE FACTS!NEW HYDRAULICS GIVE NEW PERFOMANCEThe dust boot and hydraulic seal are vital to brake performance. The piston and inboard shoemust move freely. The piston seal not only prevents fluid leakage but also acts as a selfadjusting mechanism. The seal grips the piston. When sufficient lining to rotor clearance existsthe seal allows the piston to slip out. As the seal grips the piston it is stretched out whenhydraulic pressure is applied, and returns to normal when pressure is released pulling the pistonback with it. This action give running clearance.If gummy residue collects on the piston and cylinder bore, piston movement will be restricted andinsufficient lining clearance will develop, leading to rapid wear.Always replace the dust boot, seal and clean the piston and bore with every reline.OLD HARDWARE WEARS OUTNEW HARDWARE EXTENDS LINING LIFECaliper pins and sleeves rust and cannot be cleaned and reused. The caliper pins and sleevesride in rubber bushings. The rubber bushings deteriorate with age, heat and stress. Runningclearance wear of the pads depend upon the proper relaxation of the rubber bushings andsleeves. Drum brake return springs and hold-down parts wear out and lose their tension due toheat, constant stretching, and compression when the brakes are applied and released. Adjustingparts are also affected by stress and heat. Adjusting cables stretch, and worn adjusting screwsprevent the brake assembly from adjusting. If these parts are not replaced, the results will behigh lining wear and poor brake performance. Other hardware that must be replaced includesanti-noise clips and springs for quiet brake operations.DO THE JOB RIGHT!USE NEW HARDWARE AND HYDRAULIC PARTSFOR DISC AND DRUM BRAKE JOBS YOU CAN RELY ON! 2002 Federal-Mogul Corporation
When To Use Chemical Compounds During Disc Pad InstallationThe Federal-Mogul TEC Center recommends different uses of chemical compounds wheninstalling disc brake pads depending on the pad design. The type of design will determine whatchemicals a technician should and should not use on the back of the disc brake pad plates toprovide optimal function and service life with Wagner disc pad products.Disc Pads with Integrally Molded InsulatorsWagner ThermoQuiet , with its patented IMI Sound Insulator design, requires that NO chemicalcompounds (EMP, Silicone Lubricants, Moly Lube, etc.) be placed on the insulator area of thedisc brake pads. ThermoQuiet with the IMI Insulator is designed to be installed right out of thebox and onto the vehicle. Use of chemicals on the insulator may reduce the insulator’seffectiveness.Disc Pads with Shims AttachedWhen installing disc pads with constrained layer shims already attached to the disc pad plate, theTechnician should put a slight coat of Wagner’s Silicone Lubricant on the back of the shim. Thiswill aid as an additional noise suppressant.Technicians should NOT put any other chemical compound on the back of the shim. Compoundsthat are tacky might cause the shim to be pulled from the back of the disc pad plate. Chemicalcompounds such as Moly Lube or other products that have a petroleum base should not beutilized. Petroleum base products can have an adverse effect on rubber in a brake system.Disc Pads without Shims AttachedWhen installing disc pads that do not have shims attached (as per OE) the technician shouldutilize the EMP compound that is included in the box with the pads. EMP compound should beput on the back of the disc pad plate where there is contact with the outer caliper fingers orcaliper piston when installed. EMP compound should be applied in a thin coat approximately 1.5– 2.0 mm thick on the back of the disc pad plate 10 to 15 minutes prior to the installation of thedisc pads. This will allow the EMP compound proper cure time. If time for curing is not allowedthe EMP compound will be ineffective as a noise suppressant.GeneralOn all disc brake designs, the caliper rails or abutments (where there is metal-to-metal contactwith the disc pad plate) should be cleaned and lubricated with Moly Lube. Guide Pins should belubricated with Wagner’s Silicone Lubricant. Moly Lube or petroleum based products should notbe utilized with caliper guide pins as it will adversely affect the rubber guide pin boots. 2002 Federal-Mogul Corporation
BBrraakkee NNooiissee – Is it the Fault of the Disc Pads or the Rotors?Many service technicians are experiencing comebacks on disc brake pads soonerthan they expect due to noise. In most cases, the brake rotor is the culprit.Proper rotor surface and cleaning are critical to overall braking performance. TheFederal-Mogul Technical Training Center and the St. Louis rotor & drummanufacturing facility have teamed up to provide the following information.Rotor Surface’s Impact on Brake NoiseThe smoother the rotor, the better. When dragging a fingernail over the rotor surface, itshould feel glass smooth. The proper rotor surface is critical in reducing or eliminatingbrake noise comebacks. New Wagner brand rotors are machined to a mirror-likefinish, requiring no additional machining or preparation prior to installation.However, when refinishing brake rotors, most shop lathes will require a non-directionalfinish to obtain the proper rotor surface or RA. A non-directional finish is necessary tobreak off the "mountain peaks" that are produced when the rotor is turned using a shoplathe. Otherwise, these fragments break off during initial brake application and end uptrapped in the “valleys”. Eventually the fragments end up embedded in the pad, causingnoise.A non-directional finish will also reduce the phonograph record type grooves, which cancause noise. The grooves prevent the proper rotor surface area from contacting the discpad. As a result, the rotor’s contact points will overheat, hardening the contact points.The contact points will eventually break off and end up embedded in the pad, eventuallycausing noise when they contact the rotor.Installing “softer” disc pads to compensate for a rough rotor surface will result inincreased dusting and accelerated pad wear. Therefore, optimal braking performancerequires a smooth rotor surface.A Note Regarding Brake LathesMany technicians have reported very good results using the newer, more expensiveround bits. Older lathes may have significant wear in the bearings, which will preventthe rotor being held true during machining. Speed in a shop certainly means money, butit should not take precedence over required maintenance of equipment and propermachining processes. 2002 Federal-Mogul Corporation
Cleaning the Rotor and Its Impact on Brake NoiseProper cleaning of resurfaced rotors must be done. This is one of the most overlookedareas. The proper way to clean a resurfaced rotor prior to installation is to use plain oldsoap and hot water and a scrub brush. This will clean the particles out of the "valleys".Brake cleaner spray may not clean fragments from the “valleys”. Subsequently, thefragments become embedded in the pads, eventually causing noise. Try the twomethods (brake cleaner spray vs. soap and water). Using the "white paper towel test",you’ll discover the soap and water method is the most effective.Rotor Refinishing Procedure Check lateral runout and parallelism prior to cutting Ensure tool bits are sharp and brake lathe is in good operating conditionSp
3. front disc brakes very sensitive to light brake application 4. excessive pedal effort 5. rattles or brake squeal 6. brake chatter, roughness or pulsation 7. premature rear wheel lock-up under hard brake applications 8. scraping 9. dragging brakes 10. excessively hot brakes and failure to release 11. brake pedal can be depressed without ...