[e90yyc]

Metallic noise when d/s rear wheel is turned... Sounds like something rubbing, but I can't figure out what it could be. Noise goes away when I remove the brake disc and spin only the hub

What confounds me most is that the noise only occurs for about 90 degrees of the rotation... I'd think that if a splash guard was rubbing, it would be audible all the time.

Here's what I've done:

- Adjusted parking brake using correct procedure (lock cable in service position, etc...). Before making the final adjustments I also tried loosening the parking brake shoes on that wheel to remove any possibility they are rubbing, but am still hearing the noise

- Inspected brake splash guard and checked clearance. As far as I can tell everything is okay.

By all accounts removing the splash guard is an unmitigated pain in the balls.... that is of course unless I wanted to just cut it off entirely, but I don't. So I'd say that option is out.

Looking for ideas here. Could prussian blue help in determining which surfaces are making contact?

For any astute listeners out where wondering what that other noise is, it's my diff. I have no idea whether it's gear or bearing related, but I've got a low-mileage replacement currently on the way. Believe it or not I was actually hoping it was just wheel bearings, but it looks like the joy of replacing those will come later down the road.

Edit: Forgot to mention that it’s definitely coming from that wheel. The video didn’t localize the sound at all.

[jsunma]

That is interesting...and I'm staying tuned to see what folks here turn up. My car is doing something similar, and I'm beginning to wonder if it's a CV joint. The scraping sound is not one typically associated with a CV joint though. On my car, I was getting rear wheel bearing noises, replaced the bearing (truly an awful job IMO) and while the noise is less, it's still there...coming from that same side that I replaced the bearing.

One quick check you could do is to remove the rotor and caliper and then turn the hub (like you are doing in the video, except the hub and not the rotor). That way you'll have eliminated all possible brake interference (parking as well as pads/caliper). Also you'll be able to get a better look at the splash shield and make sure it's not catching something (which I very much doubt). Anyhow, that's not much work to check.

Do you hear the noise when driving, and if so does it get worse when turning one way or the other (particularly right, as you feel that the left wheel is making the questionable sound)?

You're right, you cannot remove the splash shield entirely w/o removing the hub...which also means replacing the wheel bearing as you trash the bearing by pulling the hub.

How does the prussian blue thing work? I haven't heard of that before.

[e90yyc]

Originally Posted by jsunma

That is interesting...and I'm staying tuned to see what folks here turn up. My car is doing something similar, and I'm beginning to wonder if it's a CV joint. The scraping sound is not one typically associated with a CV joint though. On my car, I was getting rear wheel bearing noises, replaced the bearing (truly an awful job IMO) and while the noise is less, it's still there...coming from that same side that I replaced the bearing.

One quick check you could do is to remove the rotor and caliper and then turn the hub (like you are doing in the video, except the hub and not the rotor). That way you'll have eliminated all possible brake interference (parking as well as pads/caliper). Also you'll be able to get a better look at the splash shield and make sure it's not catching something (which I very much doubt). Anyhow, that's not much work to check.

Do you hear the noise when driving, and if so does it get worse when turning one way or the other (particularly right, as you feel that the left wheel is making the questionable sound)?

You're right, you cannot remove the splash shield entirely w/o removing the hub...which also means replacing the wheel bearing as you trash the bearing by pulling the hub.

How does the prussian blue thing work? I haven't heard of that before.

I'm realizing I may have omitted some key details... With the brake rotor removed there is no longer a noise. As far as I know I'm not hearing it while driving, but I could be mistaken.

Prussian blue (also know as engineers blue or marking blue) is a compound that can be applied to two surfaces to test for trueness, check meshing patterns, etc. So in my case, I'm hoping it could help show me precisely where this rubbing is occurring.

Frankly I don't see how that sound could be coming from an axle, but I'm far from an expert in this area.

The other noise (if you can hear it) is coming from my rear diff. I suppose I'll know if it was actually my wheel bearings once I install the replacement diff. Hoping that I'm not wrong though.

[e90yyc]

Anyone?

[mweisdorfer]

Originally Posted by e90yyc

Anyone?

Emergency brake? Is is running on the inside of the rotor?

[Jagtem]

If you're certain it's not making any contact with the brake shield, I'm inclined to think it's gotta be parking brake related. Perhaps the parking brake shoes are not perfectly aligned inside the rotor? Maybe try removing them altogether to see if that makes a difference?

[mweisdorfer]

Originally Posted by e90yyc

Anyone?

The heat shields are notorious for running on the rotors too.

[e90yyc]

Originally Posted by mweisdorfer

Emergency brake? Is is running on the inside of the rotor?

That was my first thought, but doesn't seem to be the case...

Before carrying out the correct adjustment procedure, I tried "loosening" the shoes at that wheel to remove any chance they could be rubbing (parking brake in service position and turned adjuster screw to loosen (move shoes closer to hub/inward). Still made the same noise...

Next step is going to be to remove the parking brake shoes altogether, and then see if the noise persists.

[e90yyc]

Originally Posted by Jagtem

If you're certain it's not making any contact with the brake shield, I'm inclined to think it's gotta be parking brake related. Perhaps the parking brake shoes are not perfectly aligned inside the rotor? Maybe try removing them altogether to see if that makes a difference?

Thanks!

I'm not certain -- that's the problem. Also why I thought it might be good to use some marking blue to determine whether there is any contact being made with the brake shield. I think I'll still give that a try, unless someone else has a better suggestion on how to accomplish this.

I'll try taking them off. I even sanded off all the rust inside the rotor where the parking brake shoes make contact. Given how subtle the noise is and how there is really no change in resistance when turning the wheel, I thought surely if it was the shoes, removing the amount of rust I did would have gotten rid of the noise... No joy though.

[mweisdorfer]

Originally Posted by e90yyc

That was my first thought, but doesn't seem to be the case...

Before carrying out the correct adjustment procedure, I tried "loosening" the shoes at that wheel to remove any chance they could be rubbing. Still made the same noise...

Next step is going to be to remove the parking brake shoes altogether, and then see if the noise persists.

Yep, there is a pretty detailed procedure in the Bentley Repair Manual on that.

[mweisdorfer]

The heat shield can only be taken off when you do a bearing DIY, from understanding. Unless you just cut them off like you said.