I've got a situation with a 1993 850 that I wanted to see if anyone here had any input on. There's an intermittant squealing noise that sounds like it's coming from the front right (passenger side) wheel, but it's hard to tell. The noise will go away periodically during a drive, and sometimes come back. It only happens when the car is moving, and its pitch is proportional to wheel speed but not engine speed (so I've ruled out any possibility that it's coming from the engine or transmission).

The brake pads (the first obvious suspect) have plenty of life left in them so I don't believe them to be the problem. The noise does not stop during braking, but simply lowers in pitch until it stops as the car slows to a stop. Because of this I don't believe it to be pad squeal (wouldn't it stop while braking if it were?).

Lifting the car and turning the wheels by hand produces no noise, so I don't believe it to be wheel bearings either.

It crossed my mind that it could be coming from the parking brake shoes in the rear hub as well. The parking brake doesn't work very well and I suspect the shoes are adjusted too loose. Given that they are too loose (as opposed to too tight) I don't really think that could be the problem but I thought I'd mention it.

Does this sound familiar to anyone? Is there any more information that would be helpful?

Edit: I just wanted to add that there is no brake judder or anything to suggest that the rotors are warped.

 

My breaks were also noisy and I fixed it by cleaning and lubricating them...
I would suggest that you remove your break pads and clean the caliper and break pad guides with break cleaner and a toothbrush or wire brush. Then apply break lube (I think it's silicone based) to all of the the little metal tabs on the sideof the pads, and the back of the pads. Then reassemble the breaks.

FCP Groton sells "Brake Pad High Temperature Silicone" for $8.00. Part number 1161325. That's what I used.

good luck!

 

What kind of pads are you using? I have had squealing brakes on anything except OEM pads.

 

elchingon2002: I had considered that it might just be normal brake squeal and I'm hoping it is. I'm going to try to make time this weekend to take out the pads and clean everything as you describe. What worries me is that the noise sounds a little too much like a metallic scraping, perhaps like some little sheetmetal piece of brake hardware scraping against the rotor, although I don't think it's something on the pad surface because:
[ol][*]The rotor isn't obviously gouged up.[*]The noise isn't always present.[*]It doesn't stop or increase when applying the brakes (even when applying them hard).[/ol]Even so I do hope to be able to take them apart and give them a lookover and a cleaning this weekend.

JimKW: I'm not sure what kind of pads are on there. I've had the car for about a year and the pads were apparently replaced shortly before I got it. I believe the previous owners had it serviced at the dealer so the pads are probably OEM. The sound has only started fairly recently so it's doubtful that it's from a botched install.

Any more input is welcome. As it stands I'll monitor it this week as much as I can (it's my girlfriend's daily driver so I don't get to listen to it every day) and plan to take a closer look this weekend. Thanks for the help so far.

 

I was planning to disassemble the brakes and clean everything today but of course I overlooked the fact that I don't have the right size allen wrench to remove the guide pin and take the caliper off, so I won't be doing that today.

I'm getting worried that the sound might be from the wheel bearing, though. Wouldn't a normal brake squeal change sound when the brakes are applied? As in, it might only happen when applied, or stop when applied? This sound isn't affected by applying the brakes (hard or soft) except that it decreases in pitch as the car slows down.

I still can't hear anything when turning the wheels by hand, and I don't feel any play grabbing any wheels by the top and bottom and trying to shake them (any wheels.. though I'm pretty sure the sound is coming from the front), so I'm kind of at a loss.

 

once I heard noise I thought from the front brakes, turned out to be rear brakes... used shims on rear brakes.

 

And this may be coming from the rear wheels. In any case, I can't feel any play in any of the wheels, but if brake shims were the problem, wouldn't you expect the sound to change when the brakes are applied?

 

I'd second the advice to remove your calipers and pads and clean/lube them. My guess would be it's some kind of debris that got wedged between your pad and rotor...possibly on the inside so you can't really see if it's scratching the rotor. I've always used synthetic grease on the back of the pad and both sides of the shims and never had any squealing from the brakes. This is a quick and cheap way to narrow down what your problem really is. If it works, great...if not, at least you know it's not the brakes.

 

Check the rears.
Where the cross looking spring mounts on the pins. Sometimes the spring isn't all the way seated on the pin and slightly scraps the rotor making noise.

 

Just to close this up.. thanks for all the tips. In this case, though, it turns out the brakes weren't the source of the noise. I ended up taking the car to a mechanic when I couldn't narrow it down myself, and it turns out the bearing hub's seal was coming out and rubbing or resonating against the axle at speed. So, it was the bearing after all, but the bearing wasn't bad quite yet.

In retrospect, I should've referred to the noise originally as a screeching instead of a squealing...