Strange noise when braking...

[RichInMich]

Got a weird situation to bring up - had my car in a few months ago to the dealer (13 SHO w/ PP) to have my rotors turned under warranty. After that was performed, the car sounded AWFUL whenever I applied the brakes. Sounded like they forgot to put the pads back on and it was straight metal scraping and grinding (which of course was not really what happened).

I attributed that to be cheap rotors (accustomed to that coming from the previous 19 years of owning GM vehicles), so I went about ordering new rotors and pads.

I could not get the rotors off when I went to do this (had a breaker bar out loaned to someone else), so I just ended up replacing the pads at first with the intent of replacing the rotors in a week or two later once I got all my tools back.

Well the noise still remained, though slightly improved. A few weeks later, I did end up replacing the rotors but the grinding sound still remains!

What in the world could this be? The new rotors have been on there for a few weeks, I've probably put 600 miles on them (new pads probably have 1000 miles on them).

Of course I can't take them back to the dealer now, he'll blame the problem on me (even though I've replaced pads and rotors at least a dozen times previously and have never had any issues at all).

Someone suggested the old rotors may have damaged the new pads in the two weeks they were on together, and told me to go buy a new set of pads to eliminate that as a possibility.

To summarize - never a sound or problem until the brakes are applied. No signs of uneven wear or warped rotors, just a weird metal on metal deep grinding feeling. The feeling is a lot worse "at speed" (i.e. 60+ mpg).

If this were a bad alignment, I'd feel it during normal driving conditions (someone had suggested maybe they couldn't get the rotors off so they pounded them hard and threw the car out of alignment - find that hard to believe though).

As always, thanks for your input.
-Rich

 

[SHOdded]

Here's a checklist to see if it is still somehow a brake problem. It is possible that a wheel bearing has gone bad, based on the observation at speed. Usually will be worse turning one way or the other unless both sides have simulaneously quit.

 

[sourcec0d3]

Did you inspect and lubricate the caliper surfaces where need be? I just did my rears for a loud noise and although the calipers weren't seized up i know the sound of when one is and sounds like metal on metal. and being that you've just replaced the rotors and pads have you inspected the pad surfaces to make sure they're both wearing? maybe a bad caliper also.

 

[SHOdded]

BTW, what kind of pads did you install this time? Ceramics are quieter than semi-metallics, for example.

 

[RichInMich]

I did ceramic pads - but seriously, this isn't a typical "pads are wearing down" noise which I'm quite familiar with. I replaced the sliding clips for all 4 pads and applied a dab of grease on those as well as on the caliper pins. The shims on the back of the pads were new, too, and I did **** them with the stuff I have always used. It sounds like the caliper is rubbing against the edge of the rotor, to be honest - but there is no evidence of that on the rotor or the caliper.

I'll bring it into a mechanic this week and have him look at it. It's perplexing, and certainly something that the dealer did because it was a lot worse before I replaced the rotors myself (a month after he turned the rotors under warranty).