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Discussion Starter · #1 ·
Hi,

I am getting a weird mosquito-like noise from the rear passenger wheel. I can only hear it when the window is down and louder when it bounces back from parked cars or fences when I drive by.



It's a high pitch, mosquito like sound which starts manifesting at and over 45 - 50km/h.
It is not related to the RPM or acceleration and pressing the clutch does not change it. It is purely related to the car's speed on the road.

I noticed that if the car is cold, I don't get the sound, but once I drive it for about 10 minutes I get the sound.

I recently replaced the wheel bearings and rebuilt both e-brakes (new pads, mechanisms springs dust shield and rotor).
I am getting the same noise with different tires. I also have new pads and disks, the disk is not warped, I checked it using a micrometer and I only have +/- 200 microns over the entire surface, which is the same on all discs (again they are maybe 5 months old, same as pads, all OEM).

Any ideas what it could be? It's driving me insane.

Thank you in advance.
 

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Discussion Starter · #2 ·
Update:

I was able to record a video with the exact noise:
https://www.youtube.com/watch?v=GIwUCZGa1v4

The noise starts at 6seconds into the clip. It is a faint mosquito like noise.
During the recording, I used a phone and placed in on the passenger seat and had both windows down. The noise is coming from outside of the car (sounds like it's coming from the wheels).
 

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Discussion Starter · #6 ·
Update:
Changed pads to performance ceramic pads, resurfaced the disk and installed new calipers.
Also replaced all the trailing arm bushings (unrelated) and the issue is still there.

I drove the car for about 1500 kms this month in two long trips, and it seemed that after the first 400kms the noise started to randomly stop. drove it back and it would go on for a day off for another. did another 800km round trip, and then the noise went away for a week. Now it's back...
 

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2004 330Ci 115k miles
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Ok, you put one of those on a wheel spinning at 60 km/h and tell me how it goes...
Obviously, you don't touch it to any moving part as that would create noise itself and mask the noise you're trying to find. But you can touch it to various stationary parts while the noise under investigation is happening and then you can find the source. As you touch it to different parts listen for the noise getting louder or softer. When you find the spot where the noise is loudest you are close to the source.
 

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Discussion Starter · #8 ·
Obviously, you don't touch it to any moving part as that would create noise itself and mask the noise you're trying to find. But you can touch it to various stationary parts while the noise under investigation is happening and then you can find the source. As you touch it to different parts listen for the noise getting louder or softer. When you find the spot where the noise is loudest you are close to the source.
:clap: Thanks @BaliDawg. Sorry for the tone, I thought it was an automated marketing message. I will actually try that and post my findings.
 
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