Replace Disc Brakes

Front brakes on all modern cars are disc brakes. The front brakes generally provide 80% of the stopping power, and so tend to wear faster than the rear. Replacing them — pads, rotors and calipers — is quite simple once you understand the process, and can save you a great deal of money. These instructions will include a full front brake replacement. Also, having a service manual for your vehicle will save your sanity, as well as time and money. If you only need pads, or pads and rotors, but not calipers, skip the steps for replacing calipers. Repeat the steps below for each side of the car as necessary. The work will go even smoother if you ask a competent friend to help you — especially the first time you do this kind of work.

Steps

Before You Begin

  1. Consider the symptoms of the brakes; for example:
    • If the front brakes have been squealing loudly, you may need pads only.
    • If the car or brake pedal has been shaking when braking, you'll need to have the rotors resurfaced (called "turning"), or replace them.
    • If the car pulls to one side while braking, but stays straight otherwise, you may need calipers. This is a sign of uneven wear of your brake pads caused by uneven pressure in your brake lines.
    • If the brakes have a grinding noise, this means rotors are done, spent, wasted, or whatever you want to call it, just replace them.
  2. Determine the parts and tools you'll need. There are two bolts that hold the caliper to the pad bracket, and two bolts that hold the pad bracket to the steering knuckle. You may need both SAE and Metric sizes of wrenches and sockets, as well as bleeder screw wrenches. Also, you may need a set of hex (ALLEN) or star (TORX) key wrenches or a hex or star bit socket set.
    • Consider using line wrenches to remove calipers. Theses wrenches have a better bite and reduce the chances of rounding off hex nuts fitting on the hose end.
  3. Buy more parts than you think you'll need. You can always return what you don't use (keep your receipt and boxes and parts clean/undamaged). If you get caught without something while the car is apart, you may not have transportation to go buy anything.

Removing the Wheels

  1. Park the car in a clean, solid, well-lit place. Block the rear wheels with something heavy (like bricks or lumber which is small enough to jam under the wheels) to prevent the car from rolling or sliding while it's jacked up. Apply the emergency or parking brake to hold the rear wheels fast. (The vehicle's "PARK" gear will only hold one of the drive wheels, if you have a front-wheel drive car then it will hold only one of your front wheels and if you have a rear-wheel drive car then it will hold only one of your back wheels).
  2. Loosen the lug nuts before jacking the car up (do not remove lug nuts yet). If you skip this step, loosening the lugs may be very annoying, if not impossible. It is also somewhat dangerous to loosen lug nuts after a car has been jacked up.
  3. Jack the car up with a sturdy jack on a solid surface (such as a floor jack if you have concrete to work on) and lower it very slowly and carefully onto jackstands. Caution: a floor jack's wheels need to be able to roll and the jack needs to travel a little and so it must not embed (sink) into a soft floor or surface.
    • Never work without jackstands that are on solid flat surface like stepping-stones or wide scraps of strong wood to keep the jackstands from sinking, leaning or tilting and falling, etc. Position the jackstands under a solid part of the car — the frame or subframe. You can easily damage the underside of the car, or even break something.
    • Give the car a couple of good hard, small shoves from side to side; if it's going to shift, slide off the jackstands, sink into asphalt, dirt or gravel, or just twist around and fall, better to learn now while the wheels are on than when you're partially under it with the wheels off.
  4. Finish removing the wheels, and lay the wheels under the car, just to the rear of the jackstands. In case the car slips off the stands, those wheels may prevent you, your arms or head from being caught under a falling car (preventing the car from falling to the ground) if the jack stands fall over.

Replacing the Brakes

  1. Remove the caliper from the pad bracket if necessary. (Some smaller economy-car calipers are simply held together by spring-clips, and it is very easy to remove the pads and to compress the piston without difficulty.) Larger car and truck calipers are much more hefty and are bolted in place. The pads may come out with the caliper, or stay in the bracket, depending on the car. Place the caliper on top of the steering knuckle, or hang it with a piece of clothes hanger wire or any other place where its weight won't be hanging on the brake hose, and will not fall.
  2. Remove the pads and inspect them for wear. You may need to siphon out some brake fluid from the master cylinder to accommodate the fluid being forced out (by the brake caliper piston). You should remove the cap to the brake fluid reservoir and cover it with a paper towel or rag to prevent any foreign matter getting in there.
    • Some calipers have pistons that are made of ceramic or other sensitive materials, and merely prying them back with a screwdriver can crack them and require replacing the entire caliper. Consider using a C-clamp or piece of wood to force the piston back and allow the pads to be freed, as described below in installing new calipers.
    • If either pad is down to the metal pins or backing, you'll need to machine (turn) or replace the rotors.
    • This is also a good time to compare the wear pattern of the brakes on the left side of the car to the ones on the right side. If there is a vast difference, you'll need to replace the calipers or rotors.
    • Some rotors easily slide off from the wheel lug bolts, but some are made into the wheel-hub and will require getting into the wheel bearings and grease repacking see below.
    • Modern disc brake pads are ceramic, but older brake pads may contain asbestos, which can be harmful if inhaled in the form of "brake dust." If your brake pads contain asbestos, you can learn about how to clean and/or dispose of them here.
  3. Apply anti-squeal paste to the backing of the new brake pads, but do not install them yet. Keep fluid and lubricants off of the brake pad material. Some cars, especially Ford Explorers/Mountaineers, have special lubricants on the caliper moving parts, and this lubricant cannot easily be obtained separately (ask for a "heat resistant grease made for brakes" from your auto shop). Try not to remove any of this where applicable. If these parts are dry and not lubricated, consider replacing the caliper, as you will probably notice other damage or signs of problems.
  4. Inspect the brake rotors: Always resurface the rotors with a crosshatch pattern if within spec, if the rotors are too thin to resurface replace them. A fresh rotor surface is required for proper break pad bedding
  5. Inspect the brake hoses. If they are leaking by the fittings or damaged, they'll need replacing — but that is outside the scope of this article. If you are only installing brake pads, skip to the step beginning: Clean the caliper slide pins below.
  6. Remove brake rotors if turning or replacing them. On most cars, the rotor is separate from the hub. Simply slide the rotor off of the lug studs. You may need to remove a set screw and/or use a rubber mallet to loosen the rotor. You may need an impact driver (hammer it while twisting counter-clockwise) to remove a set screw.
    • If the brake rotor and hub are one piece, remove the grease cup, cotter pin, and castle nut from the axle to allow removal. (Only if necessary, unbolt the pad bracket from the steering knuckle. The bolts that hold this on tend to get frozen, so you may need to employ a hammer, breaker bar, Liquid Wrench, or a torch to loosen them.)
  7. Get the rotors resurfaced ("turned") at a machine shop or auto parts store that turns rotors. Some auto parts stores have brake lathes or a small machine shop. Call before starting your job to verify hours; most machine shops are only open until noon on Saturday and are closed on Sunday. Rotor/hub assemblies can be turned if they are not badly worn or damaged, but consider replacing them if they are grooved. The shop should refuse to turn them if they are thin or damaged.
    • The replacement parts may be expensive, especially if you're replacing the hub and its bearings instead of putting the old hub and bearings back on the car. Be aware that not all new rotor/hub assemblies include the bearings (although they may have new races in place, so that you can just "drop in" the new grease-packed bearings). You may have to install races and seals yourself, as well as pack them with grease. So a set of bearings may be a necessary purchase as well.
    • When applicable, this is also a good time to repack your front wheel bearings. Refer to your service manual or lubrication guide for this procedure. You'll need some new cotter pins and wheel bearing grease for this, as well as a pair of needle-nose pliers.
  8. Install the new or resurfaced ("turned") rotors in reverse order of how they came off. New rotors have a layer of oil on them to prevent rust while they're on the shelf. Clean this off with carb/fuel-injector cleaner; it works better than brake cleaner in this case. Reattach the pad bracket. If you are not replacing calipers, skip to the step beginning: Clean the caliper slide pins below.
  9. Replace calipers if necessary. Make sure the brake fluid reservoir is securely closed, especially if you opened it earlier to allow for fluid to expand. Remove the "banjo" bolt holding the brake hose to the caliper. This is a special hollow bolt that allows fluid to flow through it; don't damage it or lose it. Make a note of its position or orientation; you will need to install it on the new caliper in the same orientation to avoid bending and damaging the hose.
  10. Drain the fluid from the caliper into a safe container for proper disposal.
  11. Notice that the new caliper will come with two brass washers, plus rubber grommets for the slide pins, pad retaining clips (if applicable), possibly new slide pins, and maybe that hollow bolt mentioned above. Make sure that the calipers are installed with the bleeder fittings/screws in the upper or top position. If you accidentally switch the left and right calipers and install them on the wrong side (easier to do than you think!), the bleeder fittings will be in a lower position, which will result in trapped air inside the caliper fluid chamber, which will make bleeding the brakes impossible to do. Remember, bleeder screws UP!
    • When replacing the calipers it is also advisable to replace the brake hoses to the caliper.
  12. Reattach the brake hose with a new brass or copper washer installed on both sides of the hose fitting, that the hollow "banjo" bolt goes through. Reusing the old washers, or failure to put the new ones in the right place will cause the brakes to leak. Tighten the bolt firmly.
  13. Clean the caliper slide pins if you haven't done so yet. Use a wire buffer-wheel, brush or fine grit sandpaper, if you will be reusing them and any place where the pads slide against the caliper or pad bracket with a wire brush. Apply silicone brake lubricant to all of those slide locations.
  14. Compress the caliper piston, or in some cases screw them in if necessary. Yes, some caliper pistons (such as some Nissan) do actually screw in and out. If so, there will be notches for a tool to engage the top of the piston. Pressing that kind of piston in will strip the threads and ruin the calipers and pistons.
    • Using the large C-clamp: if this is the press-in kind of piston, take one of the old brake pads and place it in the caliper against the piston to place the C-clamp against. Usually a heavy duty 8" to 10" size (inner measurement) C-clamp will do, (lighter duty clamps will spring, bend or break). Slowly and evenly compress the piston back into the caliper.
    • An even easier way to compress this piston is use a special (but inexpensive and readily available) Lisle Corp Brake Pad Spreader tool (Lisle part #24400 $7.95) made specifically for this — it beats hauling a heavy 10" iron C-clamp around — plus it's much faster to use!
    • Note: Prior to compressing the piston back into the caliper it's recommended you open the bleeder screw to allow the brake fluid to come out of the caliper while you compress the piston. This keeps the dirty fluid from going up through the brake line and possibly damaging the Master Cylinder and the internal parts of the ABS System if your car has ABS. This also eliminates the mess that may occur from brake fluid that will be forced into the master cylinder.
  15. Clean up any brake fluid that may come out of the reservoir at this point. Watch out for drips on the side where the reservoir is located. (See Note above) Be careful, brake fluid will damage or remove the paint from your vehicle if it is not cleaned off instantly!
  16. Put the new pads in the caliper or bracket. You may need to employ the large flat screwdriver again, but be very careful so you don't destroy any of the pad clips.
  17. Place the caliper back into the pad bracket, and bolt it in. On some brake calipers, blue Locktite needs to be applied to the bolts that hold the caliper to its mounting point.

Bleeding the Brakes

  1. Bleed the brakes. If you have not replaced the calipers or loosened any fittings, you can SKIP to the next section. You may wish to bleed the brakes later if you determine that the brake peddle feels mushy or goes down too far.
    • You'll need a good helper for this, and do one side at a time.
  2. Use break cleaner to clean up any grease from fingers/skin and any break fluid that may have gotten onto the rotor or pads during installation. Grease and or fluid on the pads can keep your car's breaks from gripping properly and will make stopping harder.
  3. Put the wheels back on the car to hold the rotor on straight, if it is the easy removal kind of rotor (separate from the hub).
  4. Do not let the car down from the jackstands yet.
  5. Remove the rubber cap from the hollow bleeder screw, and unscrew the bleeder screw about 1/4 or 1/2 turn. This should be just enough to loosen it, being careful not to damage the screw (use a snugly fitting solid wrench, not pliers and not an adjustable wrench). Attach an appropriate size clear or rubber hose to the bleeder screw with the other end immersed in brake fluid in a jar or can before depressing the brake pedal. This helps to avoid sucking air back into the bleeder screw if the pedal is let up at the wrong time.
  6. Have your assistant slowly depress the brake pedal until it's at the floor and keep there until you tell them to let it back up. Some fluid may flow out or you may see bubbling from the tube in the jar while only air is coming out. While the pedal is at the floor, close the bleeder screw. Have your assistant slowly lift the pedal. While the brake pedal is all the way up, open the bleeder screw again.
  7. Repeat the process of pressing the peddle down, closing the screw, letting up, loosening, return to pressing the peddle down, etc... until you see clean brake fluid (without bubbles) coming out of the bleeder. Always tighten the bleeder screw before letting up the peddle; final check that it is tightened securely when finished. (Some brakes are gravity-bleed, and fluid will just run out when you open the screw, and only require you to open the bleeder screw until you see clean fluid, without working the brake pedal, but the pedal pressing procedure works in all cases).
  8. Make sure the brake fluid reservoir does not run empty while bleeding the brakes. If the fluid gets too low you'll be introducing air into the master-cylinder and brake system again and will have to bleed it all out, which is even more extensive than just clearing air out of the wheel-cylinders and hoses.

Putting the Wheels Back On and Testing the Car

  1. Put the wheels back on. Tighten the lug nuts in a crossing patterning, opposing fashion so the wheel goes on straight. Example: If you have five lugs, tighten them across the wheel like drawing a star pattern with a pencil by criss-crossing back and forth.
  2. Check the brake fluid level and fill as necessary.
  3. Sit in the driver's seat and push slowly on the brake pedal a few times. The first time, the pedal may go down a ways, but the pedal should be high and firm after two or three times. This seats the pads against the rotors.
  4. Check for leaks at the brake hoses if you've replaced the calipers.
  5. Lower the car and perform a "mini" test drive, with wheel blocks situated a little behind and in front of the vehicles front and rear tires to allow some short movements rolling back and forth to test the brakes. Otherwise you may find out the hard way that your brakes aren't working. During an actual test drive, make sure the car doesn't pull, that there are no funny scraping or clunking noises, and that the brakes are working correctly.
  6. Retorque the lug nuts to be sure they are tight and put the hubcaps/wheel covers on.

Tips

  • Never push the service brake pedal while the calipers are off the rotors. The caliper piston will push out and you will have a very expensive mess of brake fluid and parts at each caliper.
  • Remember to install your new calipers with the bleeder screws in the upper or top position. If after installing you see that they are in a lower position, then you have accidentally switched the left and right calipers. Then you must remove them and reinstall them correctly. Remember, Bleeder Screws UP!
  • Use the jack from the trunk of the car if you must, but a small floor jack is much safer and not very expensive. Jack stands are good idea as well. Never work under a vehicle using just a jack! Always use jack stands!!!
  • When buying a set of wrenches or sockets try to get both SAE and Metric sizes together. Yes, sometimes you will need those Metric sizes. Alas, we live in a global economy, poor wretches that we are. There's a song in there somewhere.
  • Buy a service manual for your vehicle. Also, buy a pair of fender covers to keep your greasy paws and brake fluid off your vehicles paint, and also buy a good pair of washable mechanic's gloves. They're worth it!
  • Disc brakes squeal by their nature. Using High Temp Silicone based Disc Brake Lubrication available at all Auto Parts Stores may or will help prevent this, as will using dealership brake pads. Cheap brake pads squeal more often, but the squealing of new brakes does not indicate improper installation or safety hazard.
  • Keep your work area clean and organized, so you don't lose any tools or parts. Keep plenty of paper towels and rags handy. Also, remember to wear old clothes. Don't work in your suit, if possible.
  • Buy the best quality parts you can afford. You're already saving from not paying mechanic's labor charges, so splurge on the parts, for rice cakes!
  • When compressing the caliper, if you see that brake fluid will overflow, you can remove the excess with a clean turkey baster. Do not re-use the fluid once removed. If you need to add any, use new fluid. It's cheap, so don't try to save a few pennies on your brakes. You may need them.
  • Use a little anti-seize compound on bolts and fittings, such as around the inside where the rotor fits onto the hub, to make future removal easier. Don't use too much!
  • Always replace brakes in pairs. Pads on both sides, rotors on both sides. Calipers replaced in pairs.
  • Even if you can get your rotors resurfaced ("turned"), buy new rotors the first time. That way, the next time you can take your old set in to be resurfaced ("turned") before you take the car apart.
  • Most vehicles will not need to have the brakes bled, if you never open the hydraulic system (ie: Losing the bleeder screw, brake hoses or metal lines) unless there is a leak. This will save time and hassle from frozen or rusted bleeder screws.

Warnings

  • Unless you know your brake pads are made of ceramic and don't contain asbestos, err on the side of caution and treat them as though they do. Use a wet rag to clean dust (and dispose of the rag properly afterwards) as opposed to condensed air, which can make the particles airborne and easier to ingest.
  • Know where your extremities are. In the close quarters under the wheel-well, trying to loosen stubborn bolts, you can easily bang up your knuckles, elbow or head. Being aware of this will keep those minor bangs from becoming major ones.
  • Cars are not scary, but they are big and heavy. Take extra care to block the wheels, set the emergency brake, test the jack stands with those couple of shoves, and lay the wheels under the car while they're off, as extra safety back-ups to the jackstands.

Things You'll Need

  • Replacement parts
  • Jack stands
  • Jack (preferably a floor jack on a concrete work area)
  • Large stepping stones or pieces of lumber if not on concrete
  • Rags, paper towels, (and some cardboard to protect the floor)
  • Removal tools, usually three or four wrenches and a lug wrench
  • A clean, well-lighted place big enough to park a car in
  • Large flat screwdriver
  • Rubber mallet
  • A set of SAE/Metric wrenches and sockets
  • Hammer, breaker bar, Liquid Wrench, torch (removing stubborn bolts)
  • Brake Pad Spreader tool or large C-clamp (8" to 10")
  • Wire brush, fine sandpaper
  • High Temp Silicone Brake lubricant
  • Spray can of break-part cleaner
  • A friend (mainly for bleeding brakes)
  • Mechanics' hand cleaner
  • Jar or can with appropriate size hose for bleeding brakes
  • Brake fluid [DOT 3] or better (check your cars recommendation)

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