[krzysiekF36]

This is my first post here so I’d like to say hello!

I have an irritating issue with my F36 420d. Car is from 2015, with B47, RWD. During acceleration at 2000rpm I can hear a humming noise which is similar to broken wheel bearing. There is no way to reproduce this sound while car is parked. It occurs both in Comfort & Sport mode, only around 2k rpm. Noise is not dependent on speed, gear or turn direction. Front left, front right and rear right wheel bearings have been replaced due to another issues. Last summer I have changed gearbox & diff fluids. Driveshaft support bearing (apologies, I do not know the exact english name of this part) has been changed last week but without signs of improvement, noise is still there. Situation looks exactly the same with winter tyres and summer ones so it does not depend on “rubber” Car runs very well besides this one irritating sound.
Do you have an idea what might be the reason of such noise?

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By your excellent description, I take it that it is vehicle speed dependent and not engine rpm dependent? Does it change pitch?






Stay safe over there!

[Onizukachan]

He said not speed dependent, so I’d look at engine mounts. Perhaps one collapsed and 2k is a resonant frequency.

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You're right! Phrasing fail, I meant it mostly to see if it changes pitch.

I think you're onto something with a mount/resonance.

[krzysiekF36]

Thanks for replies

Is there a way to check engine mounts on my own? I mean without visiting the mechanic?

Stay safe!

[krzysiekF36]

Just one more thought. I'm not able to reproduce this sound while car is parked. Tried revving it slowly up to 2,5k and no suspicious noises occurred. Do engine mounts could produce it only during ride?

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Engine load is very different when driving, so it's plausible

[krzysiekF36]

I have finally checked engine mounts and all looks good. Tried also revving it moderately and more aggressive too, engine moves just a little bit so it is fine.
Do you have any further ideas how to trace the source of noise?

[krzysiekF36]

I’m still fighting with this a$$hole noise 😞 I bought and fit repair set for turbo actuator rod because one of the metal clips were missing, checked turbo heat shields, ac pipes, any loose hoses etc in engine bay… but hum/resonance is still there!

I did further tests during last long trip (4000km) and noticed new thing. When turbo is slightly building boost, the noise is barely noticeable, but when car is accelerating aggressively or from low rpm with full boost, the noise can be heard really well.

I think I have checked almost everything beside fuel filter mount and fuel lines/pipes. Still no error codes on the dash or in the code reader.

Do you have any ideas how to trace the cause of humming?

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Is it audible in a video or recording?

[krzysiekF36]

Unfortunately I am not able to record it because microphone in my mobile is pretty bad. It sounds exactly like the damaged bearing, but as we discussed it is not bearing related noise for sure because it occurs only at 2000rpm, from 30/40kmh and above

[pole1980]

It could be the diff, I had a similar humming on my M6 a while ago, and it turned out to be the differential.

Try to run the car on an elevator and have someone under the car and pinpoint the humming. Although it could result in nothing, as the wheels won't support the car, but it's still worth a try.

Are you sure they filled it with the correct amount and type of oil? The humming was there before the oil change in the diff?

[Eddamoo]

Some thoughts from me having fixed a few rattles in an F20, F30 and G02.

If its 2000RPM and not a specific speed, im assuming this happens at 2000rpm in EVERY gear above 40kmh (e.g. 5/6/7/8 in an auto), which suggests to me its purely engine resonance related as opposed to gearbox, diffs, wheels etc.

Our G02 had a similar problem - ~2000RPM under high load and only when the engine was cold (so its more clattery). It was the AC pipes where they connect to the heat exchanger in the cabin.

1. Check the panels beneath your windscreen that cover the brake fluid reservoir/master cylinder etc are fixed down properly or try removing them
2. Remove your engine cover
3. AC pipes can cause resonance to transmit into the cabin - Try different AC fan modes, close vents, recirculation etc to see if the noise differs.
4. Give everything you can see in the engine bay a wiggle and ensure its connected properly.

[krzysiekF36]

I’m sure that diff has been filled with correct amount and type of oil. I know trustworthy mechanic, he has private garage, not a big shop so I every time have a possibility to check which parts he is ordering and how the repair is done. Noise occurred for the first time about year later than diff fluid change.

Tomorrow I will try to check engine bay once again. Maybe this time with successful result 😀

edit: I’m going to call my mechanic and book a visit, unfortunately All looks fine in the engine bay. I failed to fix my car for the first time

[Zingaling18]

Pretty sure I have this same issue on my 328i but I can’t figure out what it is either. Electric buzzing/humming sounds like it’s coming from passenger side engine bay/fire wall on cold start. Only occurs when you are stepping on the accelerator in gear and it doesn’t matter how hard or lightly you step on the accelerator, the sound is constant and goes away a little after lifting off that pedal. I tried revving it in neutral also and it can’t be heard.
Usually goes away once the engine is warmed and after I restart the engine.

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Originally Posted by Zingaling18

Pretty sure I have this same issue on my 328i but I can’t figure out what it is either. Electric buzzing/humming sounds like it’s coming from passenger side engine bay/fire wall on cold start. Only occurs when you are stepping on the accelerator in gear and it doesn’t matter how hard or lightly you step on the accelerator, the sound is constant and goes away a little after lifting off that pedal. I tried revving it in neutral also and it can’t be heard.
Usually goes away once the engine is warmed and after I restart the engine.

It's unlikely, since the original post is for the diesel engine which is entirely different in equipment.


What you are describing sounds like the usual wastegate noises from the gas cars. Does it change in character if you switch from comfort, to sport, to ecopro while cold and noisy?

[Zingaling18]

Originally Posted by Enabled

It's unlikely, since the original post is for the diesel engine which is entirely different in equipment.


What you are describing sounds like the usual wastegate noises from the gas cars. Does it change in character if you switch from comfort, to sport, to ecopro while cold and noisy?

Oh I thought the original posters issue affected all the F series platform.

It does seem to be less noticeable in comfort versus when in sport mode.

[teostefan]

Hello! Is this problem similar to the sound I'm getting here?
https://youtube.com/shorts/2OplMa0Cqq0?si=krTsX90wyb3jsqbz

[krzysiekF36]

Hi! A little update from my side. I gave up and decided to ignore this noise as all major components have been checked and seemed to be fine. However, last week I was looking for something else related to B47 and found an information that various kind of vibrations/resonance noises is caused by ac pipes, but inside the cabin, not in the engine bay. I took the plastic panel which is above brake/gas pedals off, disconnected footwell light and little speaker (my car is LHD). Above gas pedal, close to the center of the car you will see ac pipes coming into the car. One of them was a bit loose in my case. I bought foam isolation which is used in heating systems for houses 😀 Diameter external is 18mm, for 13mm pipes. I put it on one of the pipes (this one which has longer straight piece) and secured with two zip ties. Total cost was about 1$ and 10 minutes of time, but it worked! Noise is completely reduced even during hard acceleration. I had no idea that two pipes which are not even touching each other can cause such loud and strange buzz. I hope this finding will help someone else too 🙂