[LionOfGosforth]

I'm new to the N54 engine and turbos in general so apologies if this question has been answered before. I did a search and found many threads related to turbo "whine" and the "siren" sound. I don't believe the noise i'm experiencing is either of those.

Anyway, this is a bone stock car and I only notice this noise when cruising, engine already warmed up. If I accelerate past 80 and then slowly decelerate to 80mph (right about 2.5k rpm's) I hear this very low pitched humming noise that slowly disappears as my speed goes below 80. If I accelerate again (slowly above 80) the noise also fades away. Only appears at 80mph and consistently so...

not sure if it's normal, expected, typical turbo behavior or a problem or not even turbo-related at all. Car has 18k miles and like I said, stock, no mods at all. Owned the car since about 16k, hoping previous owner didn't abuse the car. Other than approaching the dealer, any suggestions? Should I be worried?

Thanks all for any guidance.

[kdiggz]

i see you have an xi. my friend had this issue with his all wheel drive subaru. it ended up being a bad bushing and the differential was vibrating. my advice would be to get it on a lift and see if anything is loose under the car

[jdbretz]

It could have something to do with your tires if it only hums/makes the noise at a specific speed. I doubt it is something to worry about, but you are still under warranty so why not take it to the dealer?

[Mr. 5]

First thing to do...get tires re-balanced.

[LionOfGosforth]

Tires sounds very plausible yeah, thanks i'll get those checked out. They're the stock RFT's, no experience with RFT's either so no idea how long they last or whatever. Thanks guys, appreciate the advice.

[LionOfGosforth]

Ok so apologies for bumping such an old thread...recently replaced RFT's with new Continental DWS's and the noise remains. Only now, I also hear the sound at around 1.5-1.7k rpms as well. It's more pronounced at 2.5k rpms but like before, only occurs when the engine is warm and only when decelerating. As soon as I gently accelerate the noise goes away. I'm nervous it might be a sign of something big failing like a turbo, could also be something relatively simple. Any ideas? I'm going in for service soon but the last time I brought it in, they fobbed me off with "it's probably the tires" without even checking it out.