Auto Mechanics, what the heck is going on here?




skydivr

Jumps from perfectly good Airplanes
Donating Member
Last week I took my BMW in for a set of brakes. I bought the pads aftermarket (low dust) that I have used before with zero issues. The dealer did the work. We had to replace the front rotors (from dealer) as they were worn down. Rear Rotors were ok and reused. Pads on all 4 wheels replaced. I personally coated the recommended no squeal compound on the pad parts 24 hrs prior.

Got car back, drove it home. When I got home, it would squeal (and I mean loud enough to be heard a quarter mile away) in the last 3 MPH before stopping. I even took a video on my phone to prove just how LOUD it was. I thought, "Well, maybe they just need to set" so I drove them the next day with no improvement. Drove it again today, no improvement. When I looked at the front rotors, I saw something I'd never seen before (attached). Rear rotors look perfect like they are supposed to (no 'swirl')

Can anyone tell me what the heck is going on? Looks like SOMETHING metal on the caliper is touching the rotor, which would explain the swirl as the wheel rotates.

Car going back to dealer on Monday. Don't dare let my wife and daughter in it...

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Twobrothersbusa

Team Gixxer Racing; IDMBT #1
Donating Member
Registered
They wanted you to trade for the loaner. Going to get you back in it to try again.:poke:
 

skydivr

Jumps from perfectly good Airplanes
Donating Member
THIS is what I'm talking about (at 27 seconds is when I rolled down window and held phone outside)

 

RussellJ

Rick Rollin'
Registered
Well that definitely does not look good.

That is my professional auto mechanic diagnosis :laugh:
 

StrtRac3r

Registered
To me it looks like the non directional finish on 2/3 of the rotor... But those inner lines on the inch near the hub looks to be wearing fast. Can't say I know the cause without taking them apart but u got it done at the dealer so just tell them to take care of it.
 

skydivr

Jumps from perfectly good Airplanes
Donating Member
Btw were the pads from napa? I have had bad experiences with their carbon ceramic.
Mintex replacement
pads - Very good, all-around brake pads for everyday driving. Designed for
long life and low dust operation. They have
Germany's "E-mark" approval, meaning they met or exceed BMW's original
equipment specifications.
 

kromdom

wannabe HOON
Donating Member
Registered
That metal-on-metal squeal almost sounds like there are NO pads (gasp) or very worn out pads? Possible for you to do a visual check if that squealing unit has pads (in case the shop "forgot")? ALSO, did you perform any "bedding" procedure? Best of luck.
P.S. I am not a mechanic by any stretch of the imagination although I consider myself a PLASTIC mechanic (i.e. I hand over my credit card to mechanics)
 

skydivr

Jumps from perfectly good Airplanes
Donating Member
Brand spanking new pads and front rotors....and yes I see the pads.
 

SKnight

Registered
The swirl marks are a non directional finish that helps bed the pads in faster and better. Think cross hatch on a cylinder wall.

The squeal is a harmonic that comes from the pads chattering in the brackets. Basically there's a shim missing somewhere or they forgot to lube the slides.

Do take it back to them but from what I see and hear it's safe to drive. Well, not for your ears but it should stop fine for as long as you wish to endure it.
 

skydivr

Jumps from perfectly good Airplanes
Donating Member
Rear rotors did not require machining; they look fine and do not squeal. Pad slap on rears.

I sent a pic to who I bought the pads from (Bavarian Autosport); They said none of their OEM rotors in stock have those kind of machine marks. At first he told me that the pads will bed in a week or so, but after I showed him that pic he was astonished. Even sent pic to his BMW FACTORY rep who was surprised.

It's going back in. Yes, I hope it's only a shim or forgetful slide lube, but that will still have to be redone.
 

JINKSTER

I Love my Wife!
Donating Member
Registered
The swirl marks are a non directional finish that helps bed the pads in faster and better. Think cross hatch on a cylinder wall.

The squeal is a harmonic that comes from the pads chattering in the brackets. Basically there's a shim missing somewhere or they forgot to lube the slides.

Do take it back to them but from what I see and hear it's safe to drive. Well, not for your ears but it should stop fine for as long as you wish to endure it.
I agree on the "Pad Chatter"..like whole heartedly..could it be a missing shim?..i'm guessing "most likely not"..so?..what could it "most likely be"..3 things come to mind..

1. I would imagine your brake fluid got purty hot since you needed new front rotors and the rears turned..did you get the brake fluid changed?..power bled?..cause contaminated/burned fluid and/or air in the system would do such and?..

here's the clincher..

2. That pad dressing you put on the back of the pads?..is it that blue silicone anti-vibration shid?.if it's anything more than an extremely thin film it can result in some extremely adverse affects and finally?..

3. All of the above.

best of luck, Bill. :cool:
 

skydivr

Jumps from perfectly good Airplanes
Donating Member
Not blue, red. If I had put it on there too thick, you'd think the tech would have spoken up about it. No didn't change fluid as the previous pads where not worn down all the way. Didn't have to turn the rears. have to ask about the dressing. It's pretty thick so a thin layer would be difficult.
 

brpo

Registered
All metal to metal parts in the caliper need a thin layer of brake grease or squealing is normally.
 

Blanca BusaLess

Suffers from PBSD
Donating Member
Registered
Those marks on rotor could no have come from anything in pad as it turned. How can something that is rotating leave straight lines going in to out? There would be circular marks going around the rotor not in to out. Marks look like some sort of resurfacing machine did that?
 

JINKSTER

I Love my Wife!
Donating Member
Registered
Those marks on rotor could no have come from anything in pad as it turned. How can something that is rotating leave straight lines going in to out? There would be circular marks going around the rotor not in to out. Marks look like some sort of resurfacing machine did that?
Saiid..radial liines would be the norm..the linear lines are from chatter..they are caused by the leading edges of the abrasive pads fluttering/chattering against the disc.
 

Pecan Pouch

P-squared, Poochie or US Marine
Registered
The swirl marks are a non directional finish that helps bed the pads in faster and better. Think cross hatch on a cylinder wall.

The squeal is a harmonic that comes from the pads chattering in the brackets. Basically there's a shim missing somewhere or they forgot to lube the slides.

Do take it back to them but from what I see and hear it's safe to drive. Well, not for your ears but it should stop fine for as long as you wish to endure it.

SKnight is correct, that is a non directional finish that your seeing. Most new rotors have them. Most shops (including myself) put a non directional finish on rotors after turning them.

The squeal could be from what SKnight says or they may have put something together wrong or they may be from the type/brand of pads that are on it (the squeal could be caused by how much metallic content is blended into the pads. Different companies use different amounts in different pads. A more aggressive pad will have more in it.) Use of a ceramic pad will cut down the black brake dust that builds up on your wheels.
 



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