DIY Brake Pad Replacement – How to Change Pads and Avoid Common Mistakes
Doing your own brake job, if done properly can save a lot of money. But if a brake job is done improperly it could very well cost more than if a professional was paid to do the job to begin with. I’ve done hundreds of brake jobs in the last 25 years as a Master Auto Technician and in this article I’ll outline some of the basics. I also point out some common mistakes that beginners and even pros can make when doing a brake job.
If the car shakes when the brakes are applied, this means that the brake rotors are warped. Excessive side to side run-out causes the car to shake especially when stopping quickly from highway speeds. The rotors can be machined or resurfaced to make them true again as long as they are thick enough. If there is no pulsation or brake shake, brake pads can be replaced without machining them. In my experience though, if machining or replacing the rotors is not done when doing a brake job, most of the time there will be excessive squeaking noises after a very short time. I recommend taking care of the rotors by having them machined or replaced when doing the brake job.
Lifting the Car Safely
Sounds a little too basic doesn’t it? I’ve seen many people under cars without having a jack stand in place for safety. Hydraulic jacks are great, but what if one slips or fails in some way while someones under the car working? I can’t emphasize enough the importance of having the car safely raised with a jack stand in place, just in case the car falls for some reason. A jack stand under the car is very important for anytime work is to be done under the car, like for oil changes, starter replacement or any other job that could crush a person if the jack failed. I once worked with a mechanic that was changing his starter at home. His hydraulic jack had a slow leak and before he realized that the car was lowering gradually onto him, he was pinned under the car and couldn’t get out from under it. The compressing of his chest only allowed him to take very shallow breaths of air, which limited his ability to cry for help! Luckily a friend stopped by, saw what was happening and raised the car for him. If not for luck this could have had a totally different outcome, his mistake could have cost him his life.
Removing Wheels, Calipers and Rotors
After removing the wheels find the caliper bolts and check to see what type of head the bolts have to determine what tools will be needed. Common fasteners will have either regular bolt heads, allen or torx. Typically there will be two bolts holding the caliper and two bolts holding the caliper bracket. Usually just the caliper can be removed if just replacing the brake pads. Suspend the caliper with an elastic cord or something similar to prevent the weight of the caliper from possibly damaging the brake hose. If the rotor is being removed to be machined or replaced most of the time the caliper bracket will need to be removed as well. Rotors will either just slide off or on older style setups will be held on by the wheel bearings. Most cars today will have rotors that slide off. The wheel bearings on this design are not serviceable, meaning they are lifetime greased and can only be replaced when they fail so they are not repacked with grease during a brake job like in the past.
Pushing the Piston
Pushing the brake caliper piston back in is required to install the new brake pads. The piston slowly extends out as the brake pads wear. This is why no brake adjustment is needed for the disc brake system, it’s basically self adjusting. Big channel lock pliers can be used to compress the piston back into the caliper. There are also brake tools that can be used to push the piston back in. A big C-clamp used to be my favorite method for returning the piston back into the caliper. If working on rear disc brakes, a piston wind back tool like the KD 41540 (one of DenLors best sellers) is usually required to push and turn the pistons back in. It is recommended to open the brake bleeder screw when pushing the piston, this allows it to go back in easier and prevents possible damage to the master cylinder and/or ABS (Anti Lock Brakes) pump or valves from forcing old fluid back into the system. Closing the bleeder valve immediately after the caliper piston is pushed back in will insure that bleeding the brakes will not be necessary. If dust boots in the caliper are broken, caliper replacement is necessary. Broken boots will allow moisture and dirt to enter the surrounding area of the piston and will cause it to stick or seize. There are slides on some caliper brackets that can freeze up or seize also that can cause uneven pad wear. The slides should be taken apart and lubricated with silicone gel or disc brake grease. The slides must work freely for the brakes to work properly.
Installing the Brake Pads and Calipers
Take note of any possible differences in left side brake pads and right side brake pads. Also there is sometimes differences in inboard and outboard brake pads. Obviously the friction part of the brake pad goes towards the rotor. My uncle a long time ago, before I ever started working on cars did a brake job on his Cadillac. I remember hearing that he placed the brake pads in backwards! He ruined his brake rotors. It seems like an impossible mistake, but when you’re not familiar with what you’re doing anything is possible. With aftermarket brake pads, most of the time they will come with their own noise insulators that fit onto the back of the pads. Some will have adhesive backs that will have plastic to peel off before installing, others may have tabs built into them. Note that if these are supplied, the OE (Original Equipment) pad insulators will not be re-used. After the pads are in place, be careful not to TWIST the brake caliper hoses when putting the calipers back on. It’s a common mistake to twist them and the hoses can kink on turns.
Pump the Brake Pedal!
After everything is back together, it’s time for a test drive. But first pump the brake pedal before putting the car in gear! The pedal will go to the floor and you may be headed for a crash if you don’t. When the pedal is pumped the pistons are pushed out and the pedal becomes firm. There was an auto technician that I worked with that forgot to pump the brakes after doing a brake job. He backed out of his service bay, when he hit the the brakes the car kept going and he drove into the car that was half way up on the rack behind him. It broke the rear window of the car he was driving, luckily there was no other damage.
There are many types of brake systems but most disc brakes are basically the same. Following the steps I’ve listed here should help in replacing your brake pads. But if you are not completely confident, it’s always a good idea to ask a friend that has some hands on experience to help guide you through your first brake job.
Source by Dennis Bandy