How To Repair Brakes

Brakes, Tires and Wheels

By Rodney (Mechanics)

To repair your car’s brakes properly, you need to do a thorough job and not skip any steps to save time or money. This includes rebuilding or replacing worn-out calipers and wheel cylinders, changing the disc and drum brake hardware, resurfacing or replacing the drums and rotors, replacing the brake fluid and bleeding the lines, adjusting the parking brake and inspecting the ABS system.

If you neglect any of these steps, you may not notice any difference in your braking performance right away, but you may encounter problems later on. And that could mean the difference between a lasting and a failing brake job.

How To Repair Brakes

Not everyone can afford to do a complete overhaul of their brake system, and some vehicles may not need much work if the pads are still good. But if doing some extra work can extend the life of your brakes, improve your safety and/or boost your braking performance, you should do it.

For example, you don’t have to replace the rear brake shoes when you put new front disc brake pads, as long as the rear brakes are in good shape. But if the shoes are worn or dirty from fluid or grease leaks, you should change them — and any other drum parts that are not up to standard. Even if the shoes meet the service requirements, you should consider if they will last as long as the new pads in the front. If the shoes are thin, put new ones on the rear brakes too.

The condition of the brake calipers and wheel cylinders also determines if they need attention. You should fix or replace them right away if they show any signs of leaking or sticking. And even if they seem to work fine, you can rebuild or replace them as a preventive measure to prolong the life of your brake system. The seals in the calipers get harder over time and the piston bores get rusty. When you push a piston back into its bore to fit new thicker pads, the seal may wear faster if it rubs against a rough or corroded surface. This can cause fluid to leak and contaminate the brake pads.

Brake Repair Precautions

Before you start any brake work:

NEVER go under a vehicle that is not properly supported. That means never rely on a jack alone to keep the vehicle up. Always use a pair of support stands placed under the vehicle to prevent it from falling on you. Make sure the support stands can handle the weight of the vehicle, too. Do not use wood blocks, boxes, wheels or bricks as supports because they may slide or collapse and let the vehicle fall.

Wear breathing protection (a mask approved by OSHA, not a cheap dust mask) when you remove brake dust. NEVER use an air hose to blow brake dust off brake parts. Brake dust may have asbestos or other fibers that can harm your lungs if you breathe them in. Use a liquid cleaner to get rid of brake dust.

Do not touch any brake lines or parts in a vehicle that has an “integral” ABS system (one where the master cylinder is joined with the ABS modulator, pump and pressure accumulator) without first letting the pressure out of the system. You can usually do this by pressing the brake pedal 24 to 40 times with the key off.

More and more newer cars have antilock brake systems that can get the brakes ready before you brake (to shorten the braking reaction time), or even apply the brakes by themselves as part of the collision prevention system (automatic braking).

WARNING: Before you work on the brakes of these vehicles, you need to TURN OFF the braking system, otherwise the system might activate the brakes suddenly and make the caliper pistons push out with a lot of force. This could hurt your fingers if they are between the pads and rotors. If the pads have been taken out, the pistons can pop out of their calipers. This can happen even when the ignition and engine are off!

You can turn off the antilock brake system by finding and taking out the main power fuse for the ABS system, or by using a scan tool to turn off the system for a while. You can also disconnect the battery, but this might make you lose some memory settings in different vehicle modules.

Brake Inspection: The First Step In Doing A Complete Brake Job

Having good brakes is very important for safe driving, so the first step of a complete brake job is to check the whole brake system carefully, including the antilock brake system if the vehicle has one.

On vehicles with ABS, turn the ignition on to see if the ABS warning light works. The ABS light should come on for a few seconds and then go off if everything is okay. No light? Then you need to replace a bulb or fix a wiring problem. If the light comes on and stays on (does not go off), then you need to do more tests to find out what’s wrong with the ABS system.

On some ABS systems, there might be some problems that are not serious enough to make the ABS warning light stay on. These might be saved in the ABS module’s memory as “non-latching” or “soft” fault codes. To see ABS codes, you need a scan tool that can work with ABS.

Next is the brake system itself:

Press the brakes and start the engine. Does the pedal go down a little? That’s good because it means a good vacuum booster. No boost might mean a hole in the booster diaphragm or vacuum connection.

How does the brake pedal feel? Is it hard? A soft or squishy-feeling pedal usually means air in the lines or leaks. A pedal that goes down slowly is a common sign of a bad master cylinder. Is the pedal travel normal? A low pedal might mean worn linings, the need for adjustment, bad or stuck drum brake adjusters or a low fluid level.

Do the brake lights turn on when you press the pedal? No lights might mean a bad or misadjusted brake light pedal switch or broken bulbs in the tail lights.

Use the parking brake. Does the pedal or handle move smoothly? Is it adjusted right? Does the brake light turn on? No brake warning light might mean a broken bulb or a bad or misadjusted parking brake switch. Does the parking brake stop the vehicle? Put the transmission in gear while the parking brake is on. If it does not stop the vehicle, it needs to be adjusted. Now let go of the parking brake. If it does not let go completely, the linkage or cables need to be fixed.

Open the hood and look at the fluid level and how it looks. A low level might mean a leak or worn linings. A change in color means water in the fluid and the need for a fluid change.

Take off a front wheel and see how thick the brake pads are. If they are worn down to the minimum or if wear indicators are touching the rotor, you need new linings. If the pads are still above the minimum, you may want to change them anyway if they are almost worn out or if they make noise.

Replacing Your Old Noisy Brake Pads

Change Brake Pads

You can find different brands and grades of brake pads to replace your old ones. The cheapest ones are the economy grade or “value” line pads. They may work for some vehicles, but they will not last long or stop as well as standard grade or premium grade pads. Standard replacement pads are good for normal driving and suit many vehicles. They should have similar braking performance and service life as the original equipment pads. Premium pads (ceramic or semi-metallic) are often suggested for vehicles that have problems with wear and/or noise, or for vehicles that are used in high temperature or hard driving conditions. Ceramic pads also produce less dust, so they are a good choice if you drive a European vehicle and you hate seeing black brake dust on your wheels.

Different kinds and brands of brake pads have different friction qualities, so you should replace your old pads with the same kind or better.

If your car originally had nonasbestos organic (NAO) pads, you should look for NAO pads to replace them. Or you could choose ceramic pads for more durability and less noise, or even semi-metallic pads for high temperature or hard use driving.

If your car originally had ceramic pads (which are common on many newer cars), you should buy some type of aftermarket ceramic pad. Also, if you drive a big SUV that has semi-metallic pads, you should replace them with a good brand of aftermarket semi-metallic pads.

Removing The Brake Pads

When you take out the old pads, check for uneven wear. If one pad is much more worn than the other, the caliper may be stuck. You need to fix this before you put in the new pads.

Also look for any signs of dirt (brake fluid, oil or grease) on the old pads. If the caliper is losing brake fluid, you have to rebuild or replace it before you put in new pads. The same goes for a leaky wheel cylinder in a rear drum brake. Oil or grease can come from a bad wheel bearing or axle seal.

Before you can put in the new pads, you have to push the caliper piston(s) back into the caliper to make space for the new pads (which will be thicker than the old worn pads). You can use a big C-clamp for this.

When you put in the new pads, make sure they fit tightly in the caliper mount. If any mounting shims, springs or anti-rattle clips are very rusty or missing, put in new mounting hardware. Also check the caliper bushings, pins and slides for damage, wear or serious corrosion. Replace them if needed.

Replace Brake Rotor

Brake Rotor Checks

Also look at the condition of the rotors. Deep scratches or grooves mean they need to be resurfaced. Do you see any spots, cracks or bends that are discolored? These may also mean they need to be resurfaced or replaced.

Measure runout and parallelism, too. As a general rule, the rotors on most cars and trucks should have less than .003 inches of runout, and some cars can only handle up to .0015 inches of runout. If runout is more than this, you might fix it by changing the position of the rotor on the hub (Note: you should also check hub runout, resurfacing the rotors on the vehicle with an on-car lathe, or by putting tapered shims behind the rotors.

Look at the condition of the calipers and caliper mounts. Also look if the pads are worn the same. Uneven pad wear can happen because of rust on the caliper mounting guides or keyway.

Take off a drum and look at the drum surface, brake shoes, hardware and wheel cylinder. If the shoe linings are at or below the minimum, you need new shoes. If the linings are still above the minimum but are thin, you should get new shoes to make the brakes last longer.

Look for leaks everywhere: the master cylinder, proportioning valve, steel brake lines and rubber hoses, and ABS parts if the vehicle has them. Have someone help you press the brakes while you look under the vehicle. Rubber hoses should not get bigger under pressure. Any hoses that are worn, cracked or get bigger under pressure need to be changed.

Minimizing Brake Noise

That leads us to the problem of noise, which is a big problem for many vehicles these days. Another part of the complete brake job is doing everything you can to make less noise.

Anything that makes or increases vibration makes more brake noise. This includes too much runout or roughness on the rotors, shiny linings, loose pads, or even rusty, worn or loose caliper mounts.

You may need to resurface the rotors to reduce pad vibration. You may also put in pad shims or insulators to make less vibration between the pads and calipers and new caliper mounting hardware to avoid problems here, too. Brake grease can also be put on the backs of the pads to make less noise.

Possible Cause Of Brake Noise

Brake Rotor Resurfacing

You do not need to resurface the rotors when you change the pads IF the rotors are in good shape (within the right runout, parallelism and wear specs). But there are good reasons to resurface the rotors.

If a rotor is close to the OEM minimum thickness or cannot be resurfaced without going over the spec, then the rotor is almost done and you should replace it. If the rotor is at or below the minimum thickness, you have to replace it.

Old rotors are risky rotors for three important reasons:

-Old rotors have less weight and are less able to take and get rid of heat. This can make brake temperatures go up, which may cause fading under hard use. Pad wear will also go faster.
-Old rotors are weak rotors. If you do not replace them, they may wear down to the point where they make the brakes fail.
-Old rotors make the caliper piston(s) travel more when you press the brakes. If the distance is too much, there is a risk of fluid leaking or the piston sticking.

Another reason to resurface rotors is if the runout or shaking is more than the OEM specs. You can try to reindex the rotor, but the best way is to resurface the rotor on the vehicle with an on-car lathe. The lathe will cut the rotor to match the caliper mount or hub (depending on how the equipment is mounted).

You may also need to resurface the rotors if the parallelism between the rotor faces is more than the OEM specs (usually about .0005 in.). If the rotor is bent or has hard spots, you will have to resurface or replace it.

Hard spots that happen from getting too hot or not tightening the lug nuts evenly can make raised areas on the surface that often go below the surface. The changes in the metal of the rotor will often make the hard spots come back after a few thousand miles, so replacing the rotor might be the best way to fix it.

No matter what kind of rotor resurfacing equipment you use, always take off the least amount of metal you need to make the rotor surface smooth. This will make the rotor last longer. After you cut the rotor on a lathe, some technicians will polish both sides of the rotor with a Flex Tool or sand the rotors with #120 to #150 grit sandpaper with medium to strong force for 60 seconds on each side to make a smooth, no-direction or crosshatch finish. This is done to lower the chance of noise with semimetallic pads.

Replacing Brake Hardware

A complete brake job may also need new hardware. When you change brake shoes, look closely at the condition of the hardware — especially the very important return springs. Over time, heat makes the springs weaker and reduces their ability to pull the shoes away from the drum when you let go of the brakes. The brakes may start to drag and make the shoes wear faster and the fuel economy go down. As the springs get older, they get weaker, longer and may break. MAP says you don’t have to change the springs unless they are clearly longer, discolored by heat, broken or damaged. But because of the risks of using old springs and mounting hardware, you should put in new return springs and other brake hardware — especially if the vehicle has a lot of miles on it.

If a parking brake cable is very rusty and needs to be changed, change both cables to lower the chance of future problems.

And don’t forget the wheel bearings. The ones that you can grease in older rear-wheel drive vehicles need to be cleaned, checked, packed with new grease, put back with new seals and adjusted to specs. The ones that are sealed should be checked for too much play or roughness. If either type are not in good shape, they need to be changed.

Make sure to grease the shoe support pads on the drum backing plates with brake grease (not normal chassis grease). Also, grease the parking brake mechanism.

Bleed The Brakes

A complete brake job also needs new brake fluid. Bleeding is needed for two reasons:

-To get rid of air bubbles that may have gotten into the system while you were fixing the brakes because of a leak or a brake fluid level that was too low. The air has to be removed because it can be squeezed and can stop a full, hard pedal.
-To get rid of water in the fluid.

Brake fluid takes in water over time, which makes its boiling point lower and causes internal rust.

Changing the fluid sometimes (every two years or when you change the brakes) for preventive maintenance gets rid of the water in the brake system, makes the fluid’s boiling temperature higher and makes the hydraulic parts last longer by lowering the chance of internal rust. This can be very important on vehicles that have antilock brakes (ABS) because of the high cost of changing the hydraulic modulator assembly.

Finishing The Brake Job

When you are done with your brake repairs, press the brake pedal a few times to make sure the pedal is hard before you move or drive the vehicle. If you don’t do this, the pedal may go all the way down and the brakes may not be able to stop the vehicle!

Do a short test drive at slow speed to make sure the brakes work right. The pedal should be hard, the brakes should work without pulling or grabbing, and you should not hear any noise.

30/30/30 Brake Pad Burnishing Procedure

Do 30 stops from 30 miles per hour with a 30-second break between stops. These stops should be done at a slowing down rate of 12 feet per second or less. This means that you should stop gently and easily.

The 30/30/30 Burnish Procedure makes the pads and shoes fit the rotor and drums. It also puts the needed friction transfer on the rotors and drums for the best brake performance.

Do NOT go out and hit the brakes as hard as possible. This can make the pads shiny and cause brake noise and less stopping power. Be gentle on the brakes for the first few hundred miles of driving.

If the pedal feels soft or squishy, there may be air in the brake lines. You should bleed the brake lines again to get rid of the air. If the pedal moves too much, the self-adjusters in the drums may need to be adjusted again to make the space between the shoes and drums smaller.

If the brakes pull or grab, a caliper may be stuck or there may be oil, grease or brake fluid on the pads or rotors. Check and clean as needed.

FAQs

Q: What is the 30/30/30 Brake Pad Burnishing Procedure?

  • A: The 30/30/30 Brake Pad Burnishing Procedure is a method of breaking in new brake pads and shoes by doing 30 stops from 30 miles per hour with a 30-second break between stops.

Q: Why is the 30/30/30 Brake Pad Burnishing Procedure important?

  • A: The 30/30/30 Brake Pad Burnishing Procedure is important because it makes the pads and shoes fit the rotor and drums, and puts the needed friction transfer on the rotors and drums for the best brake performance.

Q: How can you check the wheel bearings?

  • A: You can check the wheel bearings by cleaning, inspecting, repacking and adjusting the ones that you can grease, and checking for excessive play or roughness in the ones that are sealed.

Q: What should you do before you drive the vehicle after a brake job?

  • A: You should pump the brake pedal several times to make sure it is firm, and do a short test drive at slow speed to make sure the brakes work properly.

Q: How can you check the condition of the calipers and caliper mounts?

  • A: You can check the condition of the calipers and caliper mounts by looking at the pads and seeing if they are worn evenly. Uneven pad wear can be caused by rust on the caliper mounting guides or keyway.

Q: How can you check the condition of the brake shoes and drum?

  • A: You can check the condition of the brake shoes and drum by taking off a drum and looking at the drum surface, brake shoes, hardware and wheel cylinder. You need new shoes if the linings are at or below the minimum.

Q: How can you check for leaks in the brake system?

  • A: You can check for leaks in the brake system by looking everywhere: the master cylinder, proportioning valve, steel brake lines and rubber hoses, and ABS parts if the vehicle has them. You need to change any hoses that are worn, cracked or get bigger under pressure.

Q: How can you minimize brake noise?

  • A: You can minimize brake noise by doing everything you can to reduce vibration. This includes resurfacing the rotors, installing pad shims or insulators, and using new caliper mounting hardware and brake grease.

Q: When do you need to resurface or replace the rotors?

  • A: You need to resurface or replace the rotors if they are worn, rusty, rough, bent, cracked, or have hard spots. You also need to resurface or replace the rotors if the runout or parallelism is more than the OEM specs.

Q: What are the different grades of brake pads?

  • A: The different grades of brake pads are economy grade or “value” line pads, standard replacement pads, and premium pads (ceramic or semi-metallic).

Q: What kind of brake pads should you replace your old ones with?

  • A: You should replace your old pads with the same kind or better, depending on the original equipment and your driving needs.

Q: What should you check on the old pads when you remove them?

  • A: You should check for uneven wear, contamination (brake fluid, oil or grease), and the thickness of the pads.

Q: How can you make room for the new pads in the caliper?

  • A: You can make room for the new pads by pushing the caliper piston(s) back into the caliper with a large C-clamp.

Q: What should you check on the new pads when you install them?

  • A: You should check that they fit snugly in the caliper mount, and that the mounting hardware, caliper bushings, pins and slides are in good condition.

Q: What are some signs that the rotors need resurfacing or replacement?

  • A: Some signs are deep scratches or grooves, discolored spots, heat cracks or warpage.

Q: How can you measure and correct rotor runout?

  • A: You can measure rotor runout with a dial indicator, and correct it by reindexing the rotor on the hub, resurfacing the rotor on the vehicle with an on-car lathe, or installing tapered shims behind the rotor.

Q: What are the consequences of neglecting some steps in brake repair?

  • A: You may not notice any difference in your braking performance right away, but you may encounter problems later on. And that could mean the difference between a lasting and a failing brake job.

Q: When should you replace the rear brake shoes?

  • A: You should replace the rear brake shoes when you put new front disc brake pads, if the shoes are worn or dirty from fluid or grease leaks, or if the shoes are thin and may not last as long as the new pads.