[MooMooM2]

Just got back from the track, great day at lime rock, new PR for the last day of the year, all is good. On my drive back noticed this sound when I would accelerate over 3k, mostly if not at all quite when under 2.5k, louder as it goes higher RPM. Car drives totally fine, no error messages.

Helpz!

Here is a video of the noise I tried to take

https://youtube.com/shorts/lShUp-F0JQs?feature=share

[ThreeStripes]

Check it for codes with a proper reader and take it to a indie for diagnosis. Unlikely you’ll be able to diagnose that via message board.

[MooMooM2]

I am gonna check for codes this weekend.

Also nothing to loose posting it for someone to hear, maybe someone had something similar, just looking for ideas

[MooMooM2]

I am gonna check for codes this weekend.

Also nothing to loose posting it for someone to hear, maybe someone had something similar, just looking for ideas

[MooMooM2]

no codes so that is a good sign I guess, still have not turned the car back on, would be a treat if it has gone away lol but I doubt it. Definitely sounds like its a turbo issue since only really happens after 3k, strange.

[Maynard]

Sounds more like belt noise to me, but hard to tell from the video. Good luck, hope it isn't pricey.

[MooMooM2]

Originally Posted by Maynard

Sounds more like belt noise to me, but hard to tell from the video. Good luck, hope it isn't pricey.

thank you.

yeah someone on the m3 forum said it sounds like a bearing on an idler pulley.

I could see that now, that it does sound like a bearing maybe. I have not had a chance to get my wife to rev the car while I have the hood open to see where it really is coming from.

It will probably be pricey unless I can track it down myself and fix it

[MooMooM2]

so I am 99% sure its an idler pulley. Got the part and was going to get it changed out tomorrow and low and behold the damn noise is gone. This is frustrating as I know it will come back and probably in the most inopportune moment (at the track) so I will probably still change that idler and see.

I bought one of these

https://www.amazon.com/Lisle-52500-M...541218484&th=1

what a cool tool

[MooMooM2]

Originally Posted by ThreeStripes

Check it for codes with a proper reader and take it to a indie for diagnosis. Unlikely you’ll be able to diagnose that via message board.

Just finally got around to get this fixed. I also posted on the f80 board and someone actually looked at the video and said sounds like an idler pulley so it was actually diagnosed through the message board.


This was not too hard to do but it is a pain in the ass, its tight in there and our favorite german engineers decided to put the oil thermostat lines right in the front of the bolt of the idler pulley.

I know some have been able to remove it without disconnecting those lines but i have no idea how they did that (and then be able to fit a torque tool to torque it to 60nm. Oil lines disconnected gets some extra space in there and then not too bad to get the idler in there. Also good to know how easy (and annoying) a belt change is on the s55. Easily dooable though, this probably a $1000 or more service at the dealer because they will probably remove the fan to gain more space.

Pulley seemed fine but a little gritty