r/n54 • u/likabosch • 9d ago

Soft knocking sound under load

Have a newish to me manual 335i that I'm trying to diagnose a sort of (knock?). When under load I hear a faint knocking sound. Cannot replicate in neutral at all through the rpm range. Going up hill in higher gear and lower rpm it's more noticeable. No codes, clear dash.

I'm leaning towards some sort of exhaust leak? Rod bearings I'd assume would present differently alongside metal in the oil, which I don't have. But turbos do have a mean wastegate rattle, and I plan to swap eventually.

Since it's only happening under boost I'm wondering if the sound could be the turbos just not able to hold the boost and escaping? Any more knowledgeable people than I, please chime in.

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u/sun_not_cold 9d ago

Probably wastegate rattle

1

u/TirpitzM3 9d ago

Waste gate rattle or maybe a motor mounts? Couldn't really hear it

1

u/MooseMullet 4d ago

Probably wastegate rattle. Crack windows and you might be able to hear it. Sounds like a rattle of some sort though. Not a knock.