[Nimair786]

Wanting to know is this sound is normal. When I’m cold starting the car there is this buzzing noise. The noise is pretty apparent in this video from 30 seconds onward! I wanted to know if anyone has a similar noise and if so what it is? And if not is this normal? Any ideas what this might be? Car is bone stock. The noise seems to start right before the ac turns on.


https://youtube.com/shorts/xa-6UdC5x...4aQGWZVtQeROFc

[SwankPeRFection]

That sounds like a rattle of some kind possibly in the exhaust that’s happening as the RPMs drop after the cold start cycle. Does it go away if you rev it a couple of times and let the RPMs settle down again or no?

When did this start to happen?

[Nimair786]

Originally Posted by SwankPeRFection

That sounds like a rattle of some kind possibly in the exhaust that’s happening as the RPMs drop after the cold start cycle. Does it go away if you rev it a couple of times and let the RPMs settle down again or no?

When did this start to happen?

It goes away when the car is warm.

[SwankPeRFection]

Originally Posted by Nimair786

It goes away when the car is warm.

I’d get under it and check for loose clamps and tighten them up. Also, the vbands on the exhaust side of the turbos holding the downpipes on. It’s hard to tell in the video what side it’s louder on, but if it’s on the driver side then it’s probably not the vbands as that would be on the passenger, but check anyway. Might be easier to also listen for the rattle with the hood open to narrow it down.

[Nimair786]

Originally Posted by SwankPeRFection

I’d get under it and check for loose clamps and tighten them up. Also, the vbands on the exhaust side of the turbos holding the downpipes on. It’s hard to tell in the video what side it’s louder on, but if it’s on the driver side then it’s probably not the vbands as that would be on the passenger, but check anyway. Might be easier to also listen for the rattle with the hood open to narrow it down.

That’s the plan. It’s on the driver side. Passenger side is fine. People have said that it’s the wastegate rattling to let cats warm up. What’s crazy is some have this sound and others don’t

[SwankPeRFection]

If it was wastegates, then it would be the passenger side. They’re on the exhaust side of the turbos. You said that side is quiet.

[Nimair786]

Originally Posted by SwankPeRFection

If it was wastegates, then it would be the passenger side. They’re on the exhaust side of the turbos. You said that side is quiet.

Yup you’re right. Thinking it’s something to do with the AC. When I leave the ac on the sound comes on right before the ac turns on. If the ac is off and then sound doesn’t occur

[TopJimmy]

Start car in Sport (valves open).
Use a stick to go up the exhaust top and touch a valve flap. Does the vibration stop?
Close valves and check same way. Sometimes they get a bad bushing and rattle when open or closed or both.
If yes you have a rattling exhaust valve, go see the dealership.

[Nimair786]

Originally Posted by TopJimmy

Start car in Sport (valves open).
Use a stick to go up the exhaust top and touch a valve flap. Does the vibration stop?
Close valves and check same way. Sometimes they get a bad bushing and rattle when open or closed or both.
If yes you have a rattling exhaust valve, go see the dealership.

Yup. Just letting the dealership take care of it

[mike@x-ph.com]

Originally Posted by Nimair786

Yup. Just letting the dealership take care of it

Good luck

[Needsdecaf]

That sounds nasty. Definitely not normal.

[Nimair786]

Originally Posted by Needsdecaf

That sounds nasty. Definitely not normal.

Car is at the dealership. Will update with what they say

[Nimair786]

Update: dealership called. At first they weren’t able to figure out what is was but then they had an engineer come out from BMW. It the noise is the electronic transmission pump. They said the noise is normal

[SwankPeRFection]

Why is no one else saying their car makes the same noise? Seems sus.

[Nimair786]

Originally Posted by SwankPeRFection

Why is no one else saying their car makes the same noise? Seems sus.

A couple of folks I’ve talked to have said their car makes the same noise. I’m just relaying what the dealership said so if anything happens, it’s on them!

[Shaninnik]

I have the same noise. More or less the same, but mine sounds more like electrical buzz, after cold start but then stops a minute or two after. Was at dealership couple of days ago, they said all is normal. Indie garage said normal too.

[Giak]

I have the same noise! After cold start, as soon as revs go down to idle, I start hearing that noise. It's more a clunking noise, I thought it's the distribution/timing chain vibrating. I don't hear it when the engine is warm.

[him130849]

https://we.tl/t-tQYuWHfo7H

is this normal on a cold start from front passenger side?

[VinoG80]

Did the issue fix? 2 week old M3 making same noise driving me nuts, so far have had 2 issues already!
Steering wheel noise during slow turns (sounds like plastic catching)

And long cranks when starting and car is still warm

150K car and these issues are pretty annoying