Haynes Tech Tips - Brake Pads
Modern vehicles are equipped with disc brakes on the front wheels, and many have disc brakes on the rear wheels, as well. Disc brake pads wear out over time and should be inspected for wear approximately every 15,000 miles. If you hear a loud squealing noise when the brake pedal is depressed, this is a sign that the brake pads may need replacement.
Disc brake pads must be replaced on both front or rear wheels at the same time - never replace the pads on only one wheel. Also, the dust created by the brake system can be harmful to your health. Never blow it out with compressed air and don’t inhale any of it. An approved filtering mask should be worn when working on the brakes. Do not, under any circumstances, use petroleum-based solvents to clean brake parts. Use brake cleaner only!
Brake fluid can harm your eyes and damage painted surfaces, so use caution when handling it. If you get any fluid in your eyes, immediately flush your eyes with water and seek medical attention.
- Brake System Cleaner
- Brake Pads
- Brake Anti-Squeal Compound
- High-Temperature Brake Grease
- Jack and Jackstands
- Lug Nut (or bolt) Wrench
- Filtering Mask
- Safety Glasses or Goggles
- Large C-Clamp
- Length of Wire (a straightened-out coathanger will work)
- Wrench, Socket, Allen Wrench or Torx Wrench, Depending on Caliper Design
- Purchase a service manual for your vehicle. It contains essential information for getting the job done safely and correctly the first time.
- Park the vehicle on a level surface, open the hood and locate the brake master cylinder - it’s usually mounted on the driver’s side of the firewall. Cover all painted areas around the master cylinder (fender included), remove the reservoir cover or cap(s) and remove about half of the fluid from the reservoir. It is necessary to do this so the reservoir doesn’t overflow when the caliper piston(s) is pushed back into its bore to make room for the new pads. This can be accomplished with a suction pump, a siphoning kit or an old turkey baster. Warning: Brake fluid is poisonous - don’t start the siphoning action by mouth. If you use a turkey baster, never again use that baster for cooking! Dispose of the fluid properly.
- Loosen the wheel lug nuts for the brake pads you will be replacing (front or rear), then raise the front or rear of the vehicle and support it securely on jackstands. Remove the wheels. Work on only one brake assembly at a time.
- Most vehicles have what is known as sliding brake calipers. A piston (or pistons) inside each caliper presses against the inner brake pad, pushing it against the brake disc. The outer pad is pulled against the brake disc as the U-shaped caliper body slides in response to piston movement (see illustration).
- The following photo sequence illustrates a typical brake pad replacement procedure for a sliding caliper. Some vehicles use fixed calipers, which have pistons on each side of the caliper. Your service manual will illustrate the differences if you have fixed calipers.
- A cutaway view of a typical front disc brake caliper (sliding type).
- Before removing anything, clean the caliper and pads with brake cleaner and allow it to dry – position a drain pan under the brake to catch the residue – DO NOT USE COMPRESSED AIR TO BLOW THE DUST FROM THE PARTS!
- If equipped, remove the anti-rattle spring - this kind can simply be pried off.
- Use a large C-clamp to compress the piston(s) into the caliper. DO NOT attempt this on rear calipers with an integral parking brake – see your service manual.
- On some calipers, all you have to do is remove the lower bolt or guide pin, then swing the caliper up for access to the brake pads.
- On other calipers, both bolts (guide pins) must be removed. Some models use Allen or Torx-head bolts - always use the proper tool to avoid damaging the bolts.
- Don’t ever allow the caliper to hang by the brake hose - hang it from the coil spring or other suspension member with a piece of wire.
- Once the caliper has been removed, the pads can be pulled out of the caliper.
- . . . or caliper adapter.
- Most caliper adapters have anti-rattle clips or springs that should be removed and inspected. Various designs are used – be sure to note how they are installed on your vehicle.
- Remove the anti-squeal shims from the pads, if present. Note how they are positioned - some models have only one shim per pad, but some may have two.
- Carefully peel back the edge of the piston boot and check for corrosion and leaking fluid. If any is present, replace the calipers (see your service manual).
- Check the runout of the brake disc by reinstalling the lug nuts, mounting a dial indicator as shown and rotating the disc. The reading should be within the specification in your service manual. Excessive runout leads to brake pedal pulsation or steering wheel vibration during braking. You’ll need to replace the disc or have it machined to correct the problem.
- Use a micrometer to measure disc thickness and compare it with the specification listed in your service manual. Replace the disc if it is not within specification.
- If the discs check out OK, de-glaze them with sandpaper or emery cloth – use a swirling motion.
- Apply anti-squeal compound to the back sides of both new brake pads. Allow the compound to “set up” for a few minutes before installing them (follow the instructions on the product).
- If the piston isn’t completely bottomed in the caliper, use a C-clamp and the old inner pad to bottom the piston in the caliper bore. Again, DO NOT attempt this on rear calipers with integral parking brake mechanisms – see your service manual.
- Apply a light coat of high-temperature brake grease to the upper steering knuckle-to-caliper contact surface.
- Wipe off the caliper mounting bolts (guide pins) and apply a thin coat of high-temperature brake grease to their sliding surfaces. To install the caliper, reverse the removal procedure. Be sure all clips and shims are installed correctly. Tighten the mounting bolts to the torque listed in the service manual. Repeat the procedure on the other brake assembly. When the job is complete, check the brake fluid level and pump the brake pedal until it is high and firm. Test the brakes before driving in traffic.