Scraping Noise After Brake Job

[Daughter-of-a-Yukon-Owner]

New member here. I'm 17 and graduated from my school's Automotive program three weeks ago. I thought this meant I was knowledgeable enough to save my parents some money by replacing the front brake pads, rotors, axles, and bearings on their 2000 Yukon XL 2500 for them. Everything went relatively smoothly aside from a rusted-on bearing hub bolt that needed to be sawed off and replaced. After putting the tire back on, I gave the wheel a spin and a soft but noticeable grinding noise emanated from the wheel assembly. I tried the tire on the other side and the same thing happened. I looked up the problem and most people said to drive the car normally and the noise would go away after a mile or so. I drove the car 16.2 miles to my high school and back (braking hard three or four times) but the noise didn't go away. I invited an Autotech classmate over to take a look. We tried rebuilding the caliper pistons. Turns out the dust shield isn't replaceable, and I had to buy a new caliper for the passenger side. The noise didn't go away after replacing the caliper either. Any advice for a girl who's out of ideas?

Thank you,

Daughter-of-a-Yukon-Owner

[Daughter-of-a-Yukon-Owner]

Thanks for the quick reply, Jsdirt. I'll keep your advice in mind for this job and the ones that fallow.

The morning after you replied I put the car on four jack stands and checked everything you mentioned. I found that the noise is definitely coming from the pads. It's strange because one pad has so much room in the caliper that it leans on the rotor to stay upright, and the other pad is so tight in the caliper that it constantly touches the rotor. The calipers are brand new so they don't have any fluid pressure in them yet, maybe that has something to do with one of the pads leaning on the rotor.

I grabbed caliper, and it slid half inch front to back, I thought that was normal. I'll double check that I installed the sleeves today. Thanks again!

[crankman]

For new disc brake pads , they scrape for quite a while sometime forever just a bit. I never thought nothing about it. There brand new they got to get set with the rotor surface. I think your fine.

[Daughter-of-a-Yukon-Owner]

The noise is gone!

On the topic of the loose calipers, I checked that the shims fit, but it turns out I forgot to install all the sleeves on the calipers (it's hard working on cars as a ditz ). As far as the noise goes, it was coming from the back wheels the whole time. This poor Yukon has been so abused. I wish I had pictures for you guys of how bad the back brakes were. The brake pads on the back were literally gone, and the rotors were so ruined that when my dad took it to OReilly's, they started taking pictures of it to show other customers the perfect archetype of "bad rotors". When I fixed the back rotors and pads you couldn't hear any noise at all. It went to the normal level of rubbing that crankman referred to.

Jsdirt was right, this was quite a lesson. From now on I'll be sure to check all my bases before I start ripping the car apart again.

Thanks to everyone who posted. This is a great community. Lots of knowledgeable people here.

[Jsdirt]

Usually that's one of 2 things - the dust shield got bent and is rubbing the rotor, or, chunks of rust or metal got into the tone ring for the ABS.

 

Note the word "usually". You'll learn pretty fast that nothing is set in stone in this line of work. Even jobs you've done 1,000,000 times will throw you a curve ball sometimes. Trying to figure these things out over the internet is even more of a curve ball.

 

Delving deeper into this, sometimes shims on the caliper or pads can rub the rotor if installed incorrectly, or forced on over rust, or totally wrong shims for the application, thanks to some chain parts store. Also, if the rotors are rusty where they mate up with the new hub surface, that can throw the rotor out enough to rub a caliper or caliper mount - that would be immediately noticeable as a pulsating brake pedal, however.

 

Another possibility is that there was alot of rust that should've been removed before installing the new bearing, which can make the bearing not sit where it's supposed to - long shot, but certainly possible.

 

One time I installed a caliper, but forgot to install the 2 sleeves that went over the caliper bolts (forget what make/year that was) - the caliper rubbed loudly on the rotor when I threw the wheel back on. When I took the wheel off an grabbed the caliper, and it moved a half inch front to back, I realized what I did, lol.

 

Since you've driven it enough, remove both wheels and look closely for any metal powder, just in case something isn't right. That will lead you to what the problem is.

 

If it's a 4x4, you can raise the entire vehicle up on jack stands, engage the 4x4, and with the front wheels removed observe their motion, and see if you can pinpoint where the noise is coming from. Without 4x4, you can just spin them by hand to try and track the noise down. Do it safely, obviously - moving parts will do evil and permanent damage to your body.

 

Just take your time, and look closely at everything you did. When you find out what happened, it will be an excellent learning experience you and your classmate will never forget.

 

 

One more thing I thought of: Check that new bearing bolt - make sure it's not too long and contacting the back of the hub, or nicking the studs as the hub spins.

[Doug_Scott]

If you can grab and move the caliper half an inch easily, something is wrong. The brake pads will have "shims" that go between the pad and the caliper. They also will have some form of anti-rattle device attached. Under normal conditions the brake pads will be sitting with 0 clearance between pad and rotor. Note that 0 clearance does not mean the pad is actually being applied to the rotor face, it simply means there is no room left between the rotor and the pad, so the pad will make a slight noise as the rotor rotates. Generally it is not loud enough to hear inside the truck with the windows up.

 

Did you replace or machine the rotors? Which brand/model brake pad did you install? Does the noise change when you apply the brakes?

[Jsdirt]

We all make mistakes - we're only human after all. Glad you straightened it out.

 

You'll learn, and get better & better, the more you do this. Everyone learns at different rates of speed. Some pick it up fast, others never do, and most get better with time. Main thing when starting out is, take your time and concentrate on doing it right the first time, rather than chasing the dollar. The money will come in time. Even seasoned techs can screw up quite often. It happens. The main goal should be to eliminate mistakes, rather than flagging hours. It's a tough industry in that respect.

 

The biggest problem with this industry is the incentive to haul ass. Everyone has different abilities and experience. Some people can work like crazy and get it done, and others (like myself) work better at a slower pace. Flat rate encourages speed over quality of work. I know I make more mistakes the faster I try to go. I think that's just human nature. We aren't God, and we aren't machines.

 

One of my instructors said to me once, "You can have a repair 3 ways: fast, cheap, or good ... but you can only pick 2". Lots of truth to that - if you want it fast & cheap, it ain't gonna be good.

[Doug_Scott]

We all make mistakes - we're only human after all. Glad you straightened it out.

 

You'll learn, and get better & better, the more you do this. Everyone learns at different rates of speed. Some pick it up fast, others never do, and most get better with time. Main thing when starting out is, take your time and concentrate on doing it right the first time, rather than chasing the dollar. The money will come in time. Even seasoned techs can screw up quite often. It happens. The main goal should be to eliminate mistakes, rather than flagging hours. It's a tough industry in that respect.

 

The biggest problem with this industry is the incentive to haul ass. Everyone has different abilities and experience. Some people can work like crazy and get it done, and others (like myself) work better at a slower pace. Flat rate encourages speed over quality of work. I know I make more mistakes the faster I try to go. I think that's just human nature. We aren't God, and we aren't machines.

 

One of my instructors said to me once, "You can have a repair 3 ways: fast, cheap, or good ... but you can only pick 2". Lots of truth to that - if you want it fast & cheap, it ain't gonna be good.

 

For most people, the easiest way to speed up is to skip steps. Sometimes it works, most time it doesn't. Shops that do not pay mechanics for come backs generally end up with better mechanics. Poor mechanics cannot make money when they have to fix their own come backs.

 

Being able to specialize in the shop where you work is also an easy way to make more money, eventually. Personally, I always liked a properly run flat rate environment. It kept things fair, and it made it difficult to hide your lack of skill.