servicing disc brakes how
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1. the system to prevent the master cylinder from overflowing Fluid is drained at the master cylinder or at the bleeder screw Follow the instructions in the service manual carefully to avoid getting air into the system and hampering the vehicle s braking ability CAUTION Never pour drained brake fluid back into the system Refill the reservoir with new fluid of the proper type after all work is finished on both brakes but before driving the car 2 Push the piston back into the bore following the exact service manual instructions Using a screwdriver or pry bar to do this procedure is not recommended because it could damage the piston If working on a vehicle with four wheel disc brakes a special tool is usually required 3 Position a C clamp around the caliper tighten it to force the piston into the bore A wood block might be needed to retract the piston Using a C clamp to seat the piston 4 If the piston fails to move with pressure the caliper must be rebuilt or replaced CALIPER OVERHAUL Some of the conditions that demand overhauling the caliper include fluid leaking at the piston bore a damaged dust boot or a piston that does not retract And while it is not essential it is also a good idea to rebuild the caliper whenever the pads are being replaced Because this is a rather involved job you might not want to rebuild the caliper yourself other possibilities are having the job done professionally or buying a re2. Parts 4 PLUS HOW TO SERVICING DISC BRAKES Tool And Material Checklist Brake Pad Kit O C Clamp Jack and Jack Stands O Micrometer Large Screwdriver O Service Manual Socket and Wrench O Hammer Assorted Wrenches O Needle Nose Pliers O O OOOOO00O Drift Wheel Chocks Brake Cleaner Safety Glasses or Goggles This How To Guide is des wa ed a ral o w of a vehicle repair procedure You should always refer to a service ual designed for you se te oe rn instructions Parts Plus assumes no liability for an ect procedur Most backyard mechanics are leery of doing any brake system maintenance because of the importance of brakes to driving safety Such maintenance however is well within the range of the do it yourselfer If you study a service manual and work carefully you can easily and safely do a complete brake job at home using ordinary tools and equipment GENERAL SERVICE PROCEDURES The following general service procedures and precautions apply to all disc brake systems 1 Work on only one wheel at a time Failure to do so can cause the pistons to come out of the other caliper 2 When removing a wheel be careful not to damage the rotor brake lines bleeding hardware and other components 3 Do not attempt to remove the wheel hub with the wheel and tire mounted to the vehicle The wheel tire and caliper must be removed before the hub and rotor can be removed 4 Keep the caliper rotor and pad and plate a
3. built unit ROTOR SERVICE A pulsating pedal might be caused by excessive runout or out of parallelism Excessive runout can also cause a car to pull to one side However these rotor conditions cannot be detected visually A professional can judge the extent of runout by mounting a dial indicator parallelism is checked with a micrometer by taking readings at four or more points around the circumference each the same distance from the edge of the rotor If these readings do not meet the manufacturer s specifications the rotor must be machined or replaced iS Micrometer Checking the rotor for parallelism REASSEMBLY 1 Insert the new pads into the caliper exactly as the old ones came out 2 Check the assembled brake against the set vice manual and the brake on the opposite wheel 3 Reinstall all pins springs and other removed parts being sure to replace those that need it 4 Finish reassembling the brake Replace the caliper if it was removed 5 Double check the manual to make sure everything is back together correctly 6 Follow the manual instructions for bleeding and closing the system if required 7 Be sure there is plenty of fluid in the master cylinder reservoir 8 Pump the brake pedal slowly to reseat the pistons against the pads 9 Reinstall the wheel assembly Spin it while someone else operates the brake pedal to be sure the brake is operating correctly 10 When both brakes have been servi
4. ced lower the car and tighten the lug nuts on both wheels 11 Test drive the car being alert for Unusual noises and braking patterns
5. ng light on the dashboard When the rotor wears through and contacts the face of the sensor the light is activated 3 Tactile This is actually two sensors one on the rotor face and one on the lower portion of the brake pad When the two sensors contact a pedal pulsation is created to warn the driver Brake Warning Light Sensor A Wear sensors A audible B visual and C tactile Ifa visual check of the pads must be made there are a few guidelines to keep in mind For example the friction material on nonmetallic pads should protrude at least 1 16 above the rivets on semi metallic pads it should be at least 1 32 above the rivets On pads that are bonded to the backing plate the amount of friction material should equal the thickness of the backing plate If the pads fail meet these specifications replace them keeping in mind that disc brake pads should always be replaced in axle sets To make a complete brake pad inspection following these steps 1 Engage the parking brake and position wheel chocks behind the wheels to prevent the car from rolling 2 Use a large screwdriver or the pointed end of the jack handles to remove the wheel covers from the front wheels 3 Use the wrench end of the jack handle or socket wrench to loosen the lug nuts on both front wheels approximately one turn 4 Jack up the front of the car until the wheels are off the ground Position jack stands under the car 5 Remove
6. ore removing it 1 Remove the pads Ifthe brake uses two differently shaped pads in the same caliper note which side each pad came from Removing the brake pads 2 Clean the caliper disc and entire brake assembly with a good brake cleaner If petroleum based fluids get on the disc or friction pad the brake will not work 3 While cleaning inspect the dust boot for cracks or cuts and check around the piston bore for signs of moisture If the boot is damaged or fluid is leaking at the piston base the caliper must be rebuilt or replaced 4 Be sure all parts are dry before reinstalling the pads When the brake pads must be replaced it is often recommended that the pins springs and clips be discarded and replaced as well You can buy a brake pad kit that contains pads and all of the necessary hardware as well as installation and lubrication instructions Never reuse any parts that are worn bent or corroded PISTON RETRACTION Before installing the new pads the pistons must be forced all the way back into the bores All disc brakes are self adjusting as the friction pad wears thinner the piston comes farther out of its bore to maintain a proper seat between the pad and the disc Therefore each piston must be pushed back into its bore to create room to slide the new thicker pad into the caliper On some cars the pistons must be pushed back even to remove the old pads 1 Some brake fluid should first be drained from
7. ssembly clean at all times Avoid contact with grease oil and other fluids wear safety glasses or goggles for eye protection Wire Hook Caliper Housing Rotor Hang the caliper by a wire hook 5 Do not allow the caliper to hang by the brake hose the hose could split as a result Instead hook one end of a wire coat hanger into one of the caliper boltholes and hang the caliper on a part of the chassis 6 Periodically check the fluid level in the master cylinder reservoirs 7 After repairing disc brakes check for a firm pedal action before road testing the vehicle NOTE Whenever the brakes are serviced be sure to make a thorough check for leaks in the system BRAKE PAD CHECK It is important that worn disc brake pads be replaced before they cause extensive rotor damage There are ways to determine when the pads need replacing Some make it easy for the driver they have built in wear sensors that notify you when the pads are worn In vehicles without wear sensors the pads should be inspected visually every 10 000 to 12 000 miles More frequent checks are needed if the vehicle is driven under severe conditions There are three types of wear sensors They are 1 Audible This sensor is a soft metal tab attached to the edge of the pad backing plate that emits a high pitched squeal when it contacts the rotating rotor face 2 Visual This type consists of a sensor recessed in the back of the brake pad and a warni
8. the lug nuts then the wheel and tire assembly 6 Inspect both sides of the rotor for signs of excessive wear cracks scoring corrosion discoloration or unevenness If any of these conditions are detected consult a qualified mechanic 7 Find the inspection hole on the caliper This hole allows you to view one or both linings and judge the extent of wear without removing the caliper provided the pads are bonded to the backing plates If the pads are riveted it is not possible to accurately judge the extent of wear using the inspection hole Rotor Bleeder Screw Caliper Inspection Hole Inspection hole location 8 If necessary remove the caliper and pads to inspect the pads NOTE Follow the service manual instructions On some vehicles the pads can be removed without removing the caliper it is a simple matter of removing a bolt and swiveling the head of the caliper out of the way CALIPER REMOVAL Keep in mind that these are general instructions For specific directions on caliper removal consult the service manual If the caliper is secured to its supports with bolts follow these steps 1 Push the piston back into the bore see Piston Retraction 2 Determine if the bolts are fastened on the outboard end of the caliper the side resting on the outside surface of the rotor with retaining clips mp Antirattie lip Removing an antirattle clip 3 Ifso pull the clips off and remove the bol
9. ts 4 Calipers retained by clips can usually be tapped out with a hammer and drift Those secured with Hex or Allen head screws must be removed with the appropriate wrench Top Slide Plate Tapping out the top slide plate Calipers without bolts are usually secured at the top and bottom by slide plates Remove them as follows 1 Locate the spring pins holding the slide plates There are normally two pins on each plate Spring Pins Removing spring pins from the slide plates 2 Pull out the pins using needle nose pliers and retain them 3 Use a screwdriver to tap out the top and bottom slide plates In some cases the caliper is secured on its machined guides by a support key and screw Remove the screw and then drive the key out of the anchor with a hammer and drift Once the bolts slide plates or key and screw have been removed lift the caliper from the rotor In some instances it might be necessary to push the caliper down and then pull it away from the rotor so it clears the anti rattle springs Snap Ring Support Housing Boot y Antirattle Piston Spring Seal Side Plate Shim Piston Housing Brake Hote Bleeder Pad Screw Antirattle Clips Parts of a typical caliper BRAKE PAD REMOVAL Support springs shims retaining clips or retaining pins may be used to hold the brake pads in the calipers Make a note or sketch of how this hardware fits in relation to the pads bef
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