[PranK]

This is a cross post from Reddit because it didn't get much traction there.

I have a very loud rattle at cold start idle in my 335i. It sounds a lot like a loose heat shield but I can't feel anything moving. It's around the turbos but I'm not convinced it's wastegate rattle as the noise completely goes away after 45 secs or so and doesn't happen when revving or when the car is warm. I know this is vague but I was hoping for a little direction before I just take it to the shop.

Quick edit: been watching a few wastegate rattle videos and while the sound is a little similar, mine behaved differently. The noise does not change level for the 45 seconds or so while the wastegate rattle noise peaks and drops after a few seconds. Mine definitely appears to go away after the revs drop and settle after the cold start which makes me think it's something loose.

[marvinstockman]

Noise locating:

https://www.amazon.com/s?k=mechanics..._ts-doa-p_1_13

[TheMidnightNarwhal]

Honestly I think it's the wastegate rattle. I similar thing and found it odd to how my rattle wasn't really always there when driving and once warmed up like you say, it goes away. It was mostly different from most people. And yep at one point I was also thinking for sure it was some heatshield or something.

I did the wastegate fix with the washers and it actually helped.

[PranK]

Originally Posted by marvinstockman

Noise locating:

https://www.amazon.com/s?k=mechanics..._ts-doa-p_1_13

Yeah this would be helpful.

[PranK]

Originally Posted by TheMidnightNarwhal

Honestly I think it's the wastegate rattle. I similar thing and found it odd to how my rattle wasn't really always there when driving and once warmed up like you say, it goes away. It was mostly different from most people. And yep at one point I was also thinking for sure it was some heatshield or something.

I did the wastegate fix with the washers and it actually helped.

Funny you say this. I spent a bit of time driving around my neighbourhood with the windows down this afternoon and I think I'm now leaning towards it being the wastegates. I just didn't think it sounded enough like the YouTube videos but I think I'm eating my words now. Thankfully the car came with a pretty good warranty so hopefully not much out of pocket.
Thanks for your reply!

[Serf27]

Drive against a wall with the windows down. If there’s a slight noise, you’ll hear it there and may be wastegates.
Jb4 fixed my wastegate rattle

[PranK]

Yeah I'm leaving towards mhd and would be interested to see if that "fixes" it. Given I have no low boost codes it could just be noise I guess.

[Serf27]

Mine is purely noise. No boost issues, peaking at ~18.5psi with 140k miles.
You should be fine as far as performance, just the annoying noise.

[PranK]

Originally Posted by Serf27

Mine is purely noise. No boost issues, peaking at ~18.5psi with 140k miles.
You should be fine as far as performance, just the annoying noise.

That's reassuring. Thanks mate!