[RandomHero]

2018 x3 m40i with 35k miles. Recently "inherited" from my wife after she upgraded to an x5 m50i

Only mod is a JB4 which I put on less than 2k miles ago.

I've noticed a squeak between shifts during moderate throttle in boost. It seems more prevalent while the engine is getting up to operating temp.

The noise isn't audible under light throttle or heavy throttle.

Any ideas? I was able to capture a video of the sound. It sounds very similar to a tire squeak on a garage floor.

https://youtube.com/shorts/7i5ohKs50bs?feature=share

[jsh139]

Almost sounds like a blow-off/by-pass valve. But I don't know if our X3s have these?

[Tubes23]

Doesn’t really help but my old 240i developed the same issue, mainly whilst cold.

BMW investigated (and changed the rears discs and pads as they were due) and the problem coincidentally (or not) disappeared. Ok

[RandomHero]

Originally Posted by jsh139

Almost sounds like a blow-off/by-pass valve. But I don't know if our X3s have these?

Originally Posted by Tubes23

Doesn't really help but my old 240i developed the same issue, mainly whilst cold.

BMW investigated (and changed the rears discs and pads as they were due) and the problem coincidentally (or not) disappeared. Ok

This is helpful, actually. The car has been sitting at the airport for a good bit of the last month and is absolutely filthy. I may try the simple stuff first like giving the suspension and brakes a good pressure washing to rule that out . No expecting it to be that since it's pretty loud but worth a try.

Originally Posted by jsh139

Almost sounds like a blow-off/by-pass valve. But I don't know if our X3s have these?

This is exactly what scares me. If there's pressure getting relieved somewhere (similar to a blowoff valve) that's almost surely a bad sign.