The Complete Brake Job

The Complete Brake Job
Brake system service is possibly the most all-important aspect of vehicle service. If the engine won ’ thymine originate, the customer is stranded. If the engine or transmission causes a rush or poor acceleration, the customer is annoyed. But if the vehicle won ’ triiodothyronine stop, that ’ s a large problem .
When wheels are installed, the fasteners must be tightened in an even practice to distribute clamping load, and must be tightened to the right torsion value in a consistent manner. unequal reduce of the fasteners can easily result in undue and uneven tension to the rotor hat, potentially causing distortion/warp at the rotor phonograph record surfaces. naturally, a deform rotor will lead to a bouncing/shuddering brake pedal point, ampere well as uneven wear of the friction surfaces. Never use an affect twist to tighten wheel fasteners, even though you view this as a time-saving overture. Set the shock wrench aside, grab your ( calibrated ) torsion wrench and tighten the fasteners properly to specification. Yes, this requires a few extra minutes, but it can avoid a rejoinder and a customer complaint .

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Regardless of using a new or secondhand rotor, constantly clean the rotor. That does not mean simply spraying the surfaces with a fast-evaporating brake scavenge solvent. While spray brake cleaning solution is viable and surely helps to remove surface contaminants, it ’ randomness best to handwash and scrub the disk with a mix of hot body of water and Dawn dishwashing liquid and a clean nylon brush. Why do I specially suggest using Dawn ? While I ’ thousand not a chemist and I don ’ metric ton make to know what the formula is, Dawn is merely the best soap I ’ ve always used for these applications, and it works well for removing oils and particles from the machine surfaces. You can surely follow up with brake clean solvent but don ’ triiodothyronine trust on the solvent alone. seriously, wash with Dawn and hot water, followed by a hot water rinse, followed by a cold body of water rinse ( this aids in slowing down surface flash corrode ), then dry thoroughly. once clean, wear clean disposable gloves while handling to prevent surface contamination. Rotor phonograph record cleanliness is a critical aspect of proper brake service .
Whenever servicing brake rotors, always take the fourth dimension to make a few measurements, even if the customer hasn ’ metric ton complained about a bouncing brake bicycle. measure lateral runout, magnetic disk thickness and measurement for thickness variation .
ailing machined or abused rotors, or rotors that have been warped as a resultant role of odd or over-tightening of the wheel fasteners can easily create a pulse brake pedal. apart from the annoying feel of this, if the pedal is pulsating/bouncing, this means that the pads are not in a reproducible full contact with the phonograph record surface, which results in a vary contact patch between the disk and pad, which reduces braking efficiency. Measuring lateral runout is a simple summons, and there ’ s no rationality to avoid the tax .
With the bicycle removed, install ALL of the wheel fasteners to solidly secure the rotor to the hub. Installing alone two or three fasteners can result in an erroneous runout read, which can easily fool you into thinking that the rotor has more runout than it actually has. This is particularly critical when dealing with thin-hat rotors. Uneven and incomplete deflection at the hub can easily result in heave disk that display excessive runout .
Always install and amply torsion to specification all of the wheel ’ s fasteners. In order to avoid damaging the nut seat surfaces, it ’ mho besides a good mind to install conic washers between the nuts and rotor hat surfaces. As an example, by installing lone two nuts on a five-bolt hub, you might obtain a runout reading of, say, 0.005 inches. By installing three nuts the reading might be 0.003 inches. But by installing all five, the read may be 0.002 inches, which would be within specification .
Mount a dial index to a stationary area that doesn ’ deoxythymidine monophosphate move in relation to wheel rotation ( frame of reference, strut, and so forth ). dial indicator mounts are available with magnetic bases or clamp-on designs. Position the dial indicator ’ mho diver at 90 degrees to the phonograph record surface, and push the plunger in to provide about 0.050 inches preload. then zero the gauge face. The plunger should feature a little roller yield at the tip to provide a consistent read. The piston lean should be placed about ½-inches inboard from the outer edge of pad contact. slowly rotate the rotor and locate the gloomy spot, then zero the gauge again. Using a Sharpie, make a address mark on the phonograph record at the lowest read localization. slowly rotate the rotor, observing the gauge, noting the highest reading. The difference represents the come of runout. Vehicle manufacturer specifications may vary, but as a principle of finger, the maximum allowable runout is about 0.001 inches to 0.002 inches for most applications. Depending on the rotor design, you may be able to correct for runout using an on-car lathe, or you may need to just replace the rotor. however, before replacing a rotor that you suspect of having surfeit runout, make a matchmark on the rotor hat and a corresponding roulette wheel stud, then remove the rotor and reinstall at the adjacent clockwise position and re-check runout. You may have a situation where stacked tolerances between the rotor and the hub are creating the surfeit runout. Continue to relocate the rotor on the hub, checking runout with each switch. You may be able to install the rotor with the high period of the rotor aligned with the low point of hub runout .
bill phonograph record thickness, but avoid making any decision based on only one measurement location. measure for disk thickness in eight locations. Refer to the minimal service limit ( this should be visible on the rear cavity of the rotor hat ). even if one measurement location is within the permissible thickness, measuring for thickness variation at several spots may locate a thickness that is excessively close to minimum. This is sort of a double-check of findings that result from checking runout. by and large speaking, permissible thickness version should be no more than 0.0002 inches ( some OEs may spec a tolerance range of 0.001 inches to a little as 0.0004 inches ) .
It ’ sulfur best to monitor both runout and thickness version at the like time .
Checking lateral runout and thickness variation applies to all fomite applications, and should not be limited only to vehicles that exhibit a brake pulse issue. If the caliper is mounted incorrectly ( damaged mounting bracket, etc. ), this can place the pads at an slant that is not twin to the rotor disk. As the pads wear, they will wear unevenly, possibly resulting in a taper clothing. This places inadequate coerce at the rotor, which can lead to mismatched rotor wear ( thickness magnetic declination ) .
Be aware that when correcting rotors using an on-car bracken lathe of the want to prevent metallic shaving/particles from contaminating ABS wheel speed sensors and note wheels. Metal debris can be magnetically attracted to these surfaces, which can lead to fake codes and intermittent ABS intonation. After rotor resurface, clean the sensors and tone rings, rotors, axle, etc. of any debris. Soap and hot urine work well. Don ’ thyroxine apply compressed air to blow particles away, as this can cause the particles to expand contaminant .
A brake caliper is “ simply ” a rigid housing that contains one or more pistons that move inward under hydraulic press to make the slog clash material contact the rotor disk surface. Sounds childlike adequate. however, even the best quality fresh caliper can ’ thymine operate efficiently if mounting procedures aren ’ triiodothyronine followed. Depending on the stylus ( floating or fixed ), the caliper must be mounted so that the pads are twin to the brake rotor disk. If a caliper is mounted without attention to the attachment points ( rust/corrosion on mounting surfaces, etc. ), this can create a non-parallel leave, allowing the pads to contact the rotors at an angle, minimizing entire pad contact. This results in less than efficient braking performance and taper-wears the diggings friction material. Floating calipers that are attached to a caliper bracket trust on a pair of pins that allow the caliper to slide in/out. As the brake pedal is applied, hydraulic force pushes the piston and inboard diggings toward the rotor disk, causing the caliper to slide inward, allowing the outboard motor pad to contact the rotor. If the pins are rusted, pitted, and have less than a smooth coat, the caliper will either cock ( due to inadequate sliding action between the two pins ) or dredge and solution in insufficient embroider atmospheric pressure at the rotor and/or not retract when the pedal point is released, resulting in the pad ( s ) dragging against the rotor, causing premature diggings wear, elevated brake temperature and probable sugarcoat of the rotor come on. bankruptcy to clean rust buildup and properly lubricate caliper brackets is a major cause of brake noise, premature break and increased stopping distance .
When changing pads, the caliper piston ( s ) will have moved further outbound as the erstwhile pads become thin. In ordain to install the caliper now equipped with raw and thick pads, the piston ( mho ) must be compressed in order to provide the proper clearance for pad-to-rotor disk installation. Avoid using big channel lock pliers to push a piston. This can cause the piston to slenderly cock in its yield, and you stand a chance of damaging the piston contact confront and potentially tearing the piston seal. Rather, use a dedicated piston compressor tool that provides a full-width flat face against the piston ( second ) .
If the old pads have experienced severe wear and have become very thin, the piston ( s ) have been operating beyond their intended bore path. If the pads have been worn thin, an increase area of the piston ( mho ) has been exposed to the elements for a while, possibly allowing grit to build up on the piston walls. Pushing the dirty piston fully back into its bear can result in forcing grit into the seal and digest. This can result in a awkward piston that international relations and security network ’ metric ton able to freely travel within its bear. If the piston ( s ) don ’ t travel easily and smoothly, it ’ second meter to replace the caliper .
even if piston stipulate seems OK, constantly inspect the run valve to make sure it can be opened. If a bleed valve is hard stick, you can be faced with a stubborn bleed, or even if it moves, it may not successfully seal when closed. If you suspect a bad valve and were able to remove it, installing a raw valve may or may not provide a fix, depending on the condition of the caliper ’ s female threads and valve seat. Rather than wasting time and effort to repair, just replace the caliper .
besides, check the hex size of all hemophiliac valves before you begin initiation. It ’ second park, specially for some remanufactured calipers, to have bleed valves that feature a different hex size. It can make you crazy when faced with constantly hunting for a different line wrench size if each caliper has a unlike hex size. Knowing that you have the correct line wrench ( s ) handy from the start will save clock time and aggravation. In some cases, during the remanufacturing process, correcting damaged shed blood valve female threads may have resulted in re-machining to a larger size, which may change the size of the hex ( for exercise, master calipers may have featured bleed valves that require a 10mm line wring, but the reman caliper may feature a bleed valve hexadecimal size of 5/16 inches, and so forth ). Check this from the start to avoid the motivation to travel back and away to your tool thorax .
Sliding calipers that ride on smooth-wall lead pins must be inspected for cleanliness and fluent battle of the pins to their bores. If usher pivot boots are damaged, this is a clear indication that the pins are probably scored or hoary. Simply replace it with new pins and modern boots, applying a dilute coat of high-temperature caliper peg grease anterior to initiation. Never install guidebook pins dry .
Inspect the original pads for taper or mismatched wear. Tapered wear indicates that the caliper is not aligned by rights with the rotor magnetic disk. This could be due to sticking luger pins on a floating caliper design or a damaged/bent caliper mounting bracket. eminence that another sphere to inspect are the caliper mounting bracket match surfaces, as rust/debris may have been trapped between the mounting bracket and steering knuckle during a previous bracken job, which may have cocked the bracket .
If the pads on a floating caliper feature inadequate wear, this is an indication that the caliper is not able to slide by rights. This can prevent the outboard motorboat pad from making adequate contact with the rotor, relying on the inboard pad to do most of the work. The result : the inboard pad becomes more tire than the outboard motorboat pad. This is an exercise of why it ’ s thus important to make indisputable that the caliper slide pins and bushings are cleanse and well lubricated .
If inadequate and/or excessive diggings clothing is found on a fixed caliper application, the guidebook ears of the slog backing plates may be sticking to the stainless steel steel guide/sliding clips, or the back plate ears may be stuck against the caliper, causing the diggings to be stuck against the rotor without being able to release the pad. Again, this emphasizes the need to clean/replace the pad hardware so that the pads are able to move freely within their function compass. Lube the friction surfaces ( where the pad backing plate contacts the caliper and/or guides ) with a silicone-based lubricant that offers a eminent melt point ( a dedicated bracken lubricant is recommended, designed specifically for pad/caliper lubrication ) .
When installing new pads, be sure to remove all rust/debris from the caliper in those areas where the launching pad backing plate makes reach. Test-fit the pads to the caliper to verify freedom of bowel movement. For exemplify, if the pad backing home plate ears make significant touch with the caliper resulting in a too-tight fit, in some cases when using “ dicker ” pads, the bet on plate ears may need to be cautiously filed down to obtain adequate headroom. The best approach is to use entirely high timbre surrogate pads from established manufacturers such as Brake Parts Inc., Wagner, Advics, and so forth, to obtain pads with tight quality restraint .
naturally, you never want to introduce any lubricant to the rotor disk of pad clash material. When installing new pads, make indisputable that your hands are clean and free of contaminants.

When you encounter a gloomy, sink or spongy brake bicycle, one defendant is the master cylinder. The cylinder may be bypassing, allowing fluent to leak past the piston seals internally, preventing a press buildup. This applies to all vehicles .
overlord cylinders feature brim cup seals. This design allows for the seal to improve as the pressure increases. Another have of this seal is that it does not create a vacuum when the piston retracts .
As the bicycle is depressed, the piston is pushed in the advancing direction. The lip cup seal, attached to the primary piston, generates pressure in the chief bedroom first gear, which in flex, forces the secondary piston fore, building imperativeness in the junior-grade chamber. As the press increases in both chambers, the edges of the seal are pressed against the bore of the headmaster cylinder. As blackmail increases, seal is improved .
In the manufacture work, the test routine for master cylinders is done at low pressure. Lip cup seals are more likely to fail under low pressure .
Perform an isolation trial. Use the proper tool that won ’ thyroxine damage the flexible hydraulic brake hose, clamp off all brake hoses. Press down on the brake pedal, and if the pedal is low or spongy, remove the brake lines from the overcome cylinder, and install threaded plugs in the outlets ( not plastic plugs ) .
Press down on the brake pedal point and release the bicycle and wait approximately 10 seconds. This allows the quick takeup valve to open and the air to escape through the master cylinder compensating port, and the fluid in the reservoir to enter the bore of the passkey cylinder. Once air travel stops coming improving into the reservoir, or the pedal point becomes firm, apply sparkle coerce to the pedal point, and observe if the pedal point continues toward the floor .
When the dominate cylinder ports are plugged, and the air out is bled out of the bear, the pedal should be senior high school and hard under low pedal attempt or high pedal attempt. If the pedal sinks under either condition, the seal is damaged and the master cylinder should be replaced .
A slump or soft/spongy brake pedal is generally indicative mood of a master cylinder trouble. The piston inside the maestro cylinder is likely allowing brake fluid to pass the piston seals, preventing the buildup of braking pressure. The seals feature a lip cup manner that generates sealing as pressure is increased. This type of seal does not create a vacuum when the piston retracts as the pedal is released. As the brake bicycle is depressed, the piston pushes forward. The seals allow coerce to build in the basal chamber first ( for front brakes ). press is then built up in the secondary bedroom. Damaged or worn seals allow fluid press to leak past the seal and back into the fluid reservoir. When the brake pedal is depressed, bad seals just allow the fluid to pump between the wear and reservoir alternatively of being pressure-forced through the lines to the brakes. If this is the case, and bad seals are the issue, no external leaks will result. Be aware that a cast iron master cylinder that features a poor quality hurl may have cast pores that have opened up and result in external escape. Always match for external leaks beginning. If the master cylinder caparison shows signs of external leaks, we know that we have a bad separate, so replace the master cylinder ( with proper bench run and arrangement bleeding ) before wasting time with further diagnosis. even if we however have a poor pedal, at least we have replaced a known bad separate .
When diagnosing the hydraulic brake system, first perform an isolation quiz. Using the proper clamp tool, clamp off all four bracken hoses. Depress the brake bicycle. If the bicycle is gloomy or spongy, remove the brake lines from the master cylinder and install plugs at the cable mercantile establishment ports .
Depress the brake bicycle again, and then release the bicycle. Wait for about 10 seconds. This allows the flying take-up valve in the overcome cylinder to open, allowing tune to escape through the cylinder compensating port, allowing fluid in the reservoir to enter the master cylinder bear. Once publicize stops coming up into the reservoir, or if the bicycle becomes tauten, apply light atmospheric pressure to the bicycle and observe if the pedal continues to drop to the deck .
When the master cylinder ports are plugged and air is bled out of the bear, the pedal should be gamey and hard under depleted or high pedal feat. If the bicycle drops, the sealing wax ( sulfur ) is damaged and the overlord cylinder must be replaced .
here ’ s a tip if you encounter a trouble after installing a new master cylinder : As noted by Wagner Brakes, If a newfangled master cylinder has been installed and the system is manually bled, the brake bicycle is much depress completely, moving the primary coil and secondary pistons to their extreme forward side. The elementary piston may stick tied though there are springs attempting to push it back into position. When a dominate cylinder is assembled, the seals and cylinder bear are lubricated for a positive sealing wax. This, combined with any air trapped in the system can cause a vacuum lock in the cylinder. You can verify this condition by removing the master cylinder from the booster without disconnecting the brake lines. You may notice that the piston has not returned fully rear and is not resting on the snap ring. sometimes connecting a pressure hemophiliac and opening the bicycle hemophiliac screws will cause the piston to return. You can besides tap lightly on the caparison, with bleeders assailable, to free the piston. Once the piston has returned to its discipline position and air is bled from the system, the trouble should not recur .
As anyone who is experienced with servicing brake systems will attest, we need to be careful when choosing block-off plugs for master cylinder ports, since a assortment of thread sizes and pitches are in practice, arsenic well as line-to-port waterproofing designs. Installing an incorrect plug can well result in damaging the port threads, which mechanically requires scrapping the master and obtaining another new unit of measurement .
Improper shed blood procedures can besides cause wrong to a previously-good headmaster cylinder. If a master cylinder has been operating correctly for many miles of use, and the system is then bled in the course of a normal brake job, the maestro cylinder ’ s piston seals can be damaged if the pedal is pushed amply to the floor during bleeding. Over the run of farseeing term function, the piston inside the passkey cylinder travels a relatively short outdistance. If the system was ill maintained and the brake fluid has absorbed excess moisture, the end of the piston bear may feature corrosion build-up in the end of the bore that normally never experiences piston travel. If, during the bleed process, the pedal is pushed all the way to the floor, the piston is now pushed into the corroded area, possibly damaging the seal. To avoid this during a shed blood job, you can place an obstacle, such as a jam of wood, under the pedal point to avoid over-traveling the piston .
Whenever servicing a vehicle ’ s bracken system, examine the fluid in the reservoir. If it appears dirty, vacuum the fluid out of the reservoirs and replace with bracing fluid anterior to bleeding. This reduces the risk of retaining contaminants in the hydraulic system .
Always remember to bench-bleed any master cylinder that has been emptied of fluid. An improperly bled master cylinder will result in a moo, soft pedal. This applies to a new whole angstrom well as a used master cylinder that has been drained. This involves connecting irregular transfer tubes from the output ports into the reservoir ( randomness ), filling the reservoir ( s ) and lento pushing the piston amply forward and lento releasing respective times until all traces of air bubbles are eliminated. In some cases, even after terrace bleeding via the output ports, it may be necessary to besides bleed via the headmaster cylinder ’ s bleed ports ( if so equipped ). once all trapped air has been released, be sure to keep the fluid level in the reservoirs sufficiently high to avoid exposing the release orifices at the bottom of the reservoir wells before installing the master cylinder. naturally, during system run, constantly keep an eye on the reservoir fluid flush to avoid running the overcome dry .
A mention regarding dominate cylinder reservoir fluid grade is worthy of note. A reservoir will feature min/max fluid level marks. Never overfill fluid above the soap indicator. When brakes are applied and the friction material contacts the rotors and/or drums, heat is generated in the arrangement, which causes the brake fluent to expand. The boom fluid rises the degree in the reservoir. If overfilled, the fluent can top-out and have nowhere to go, resulting in electric potential brake drag, which results in overheated brakes and premature clash material wear. Always pay attention to the reservoir fluid level. If under-filled ( below the minute line ), you run the risk of exposing the chief cylinder ports dry, which reduces or eliminates hydraulic pressure adenine well as sucking air into the arrangement .
ABS light may be on and/or false ABS energizing may occur following steering wheel bearing hub substitute on only one side of an axle .
If you diagnose a badly hub bear on one side of a vehicle and the ABS steering wheel amphetamine detector or note closed chain is integral to the bear, you may need extra repairs to restore proper ABS function. In many cases, replacing one hub bear will cause the driver to feel ABS false activation when coming to a slow break on dry paving .
faithlessly energizing is normally described as a pulse in the brake pedal when not expected. The pulsation comes from the ABS valves cycling the purportedly locked up wheel. This is due to the deviation in signal lastingness from the wheel focal ratio sensors ( WSS ) side to side. The problem is normally associated with air gap difference or wiring and/or connection integrity. In many cases, removing the WSS from the early side, if possible, and cleaning the mounting come on may repair the problem. The rust buildup actually lifts the WSS from the have a bun in the oven, increasing the air col and weakening the bespeak. Another possible emergence is play in the digest causing sine wave frequency change and or AC voltage variation. The new have a bun in the oven will have small to no play, while the remaining hub has acceptable turn but can hush affect signal intensity. Again, the remainder in bespeak from side to side may be enough to trigger assumed activation. If WSS is built-in and not serviceable, replacing the hub bearings in pairs may be the merely answer. The ABS system is activating adenine designed, so no admonitory fall will be illuminated in most cases .
If the ABS warning light is on, chances are the issue is with a bad wheel travel rapidly detector or a grind. Check the grounds first base ( establish cables grounded at the human body ) for cleanliness. If rusted/corroded, remove, clean and replace. Next, per your scan instrument ’ s direction for a specific wheel speed detector location, check the wheel rush detector. Inspect the detector connection. Remove the detector from its localization and clean the mounting sphere. Check the detector attraction for contamination.

If the electronic brake control condition module ( the ABS accountant ) is deemed defective and requires replacement, after the lines have been disconnected and the unit removed, check and clean all wrinkle connectors. Make sure that threads are clean and that each connection freely rotates on the arduous line. If rust/contaminants prevent exempt rotation, this can make reconnection unmanageable and can well result in thread damaged and/or a fluid leak. After the fresh accountant has been installed, the system must be bled, according to factory procedures. Always follow the specific routine. Otherwise you may never bleed the system by rights .
Our thanks to the following for their input signal in this article : Advics ; Raybestos ( Brake Parts Inc. ) ; Wagner Brakes

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Category : Car Brakes