the audio on the video isnt great but you can here this loud sound, and tell the difference from when its not there.
Video 1
Video 2 - you can clearly hear the sound go away in this one.
for some time now occasionally the '13 MCS i get a very loud, sound immediately when starting it.
the best way to describe it, is what an old waterpump bearings sounds like when its going out. just a metal shaft spinning but also with this sound is something in it sucking are i think.
the first inch of the throttle is more or less dead but the engine does bog down or fade, then jumps back.
so if i tap the gas a couple inches the motor revs fall off then jump back and you here this noise get slightly louder.
in maybe around a minute it FADES away which tells me that maybe the wastegate closes.
and if i shut the car off and on a few times it will absolutely go away.

i recently was able to catch it and pop the hood and its at its loudest coming from the air intake filter (CIA).
there is only one thing i know of that can produce a noise loud enough to be louder than the engine where the noise emanates form and thats the waste gate flap staying open when the engine starts.
but could the recirculating/blow off valve make this loud sound, its def. more of a turbine sound than just air sucking or blowing air which is what i would expect if it is the recirc valve, and its absolutely loud enough to hear easily and know something isnt right.

if its none of that then all i can see is the turbo bearings themselves, and they quiet down once the oile lubes up the turbo?

im at 118,900 miles so have a short window to fall under the turbo warranty but when i had it in a couple months ago they said the turbow as fine but i am not confident they pulled the downpipe and checked, but i dont know that it was happening before.
but with its random nature, i cant be certain if i take it in they are going to find anything wrong. and cant they claim the warranty on it, if it isnt bad?
I have no codes no check engine lights nothing, just this noise and poopy throttle for a minute or so if i dont restart the car a few times.

 

2 things.
1) it happened again today but i forgot my phone in the office ggrrr, so couldnt video it.
BUT... the split second before it stops i hear what i can only describe as something closing.. like a flap or vlave closing with a sucking sound.
like if you ran your vacuum hose then, not too quickly, cap your hand over the end of the host. just the "sshhhllup" sound...

i can only imagine if the wastegate was open it would be throwing codes, maybe not with a warning light but surely just a stored code. but the schwabben shows nothing...
and i have no clue what life stats to show in order to see whats happening.

2) and i have a feeling its related but cant confirm..... lately during acceleration, light or heavy i am getting a sucking/whistling noise that wasnt there before, before the normal sucking sound from the cold air intake is present, and whats wierder is most of the time its in a downward audio tone. from higher tone to lower tone.
where the normal swooshing/sucking sound from the cold air intake would be from a lower tone to higher tone as you accelerate.
almost sounds like the same PSSHSHHSSSSS when the blowoff valve kicks when you let off the gas, but not as loud and during acceleration.

not sure if its related but if its the recirculating valve, im not sure why the turbine/spinning shaft sound is there if the recirc. valve is open.

 

So today it didn’t happen and neither did that weird sound during acceleration so given what o know thus far I will say it may only happen when the loud noise happens during start up. ie the two are related

 

More info....
today it made the noise when I started it... new info it goes away 80% when the idle drops.... and you can tell whatever it is is closing or something...
then the swish noise when accelerating is back, so I played around.
what I found was that even the slightest release in pressure from your foot where the electronic throttle sensor would let off the throttle a tiny bit and the recirculating valve is kicking in making the blow off sound. It never did this before, not with such a tin release in foot pressure on the throttle.
So as you accelerate any bumps in the road or movement of your foot can cause the throttle sensor to let off the gas a teeny tiny bit and the blow off makes the swishhh sound. It’s a very short one, maybe higher pitched than normal?Then your foot pushes back down a tiny bit and it stops.
im not talking peddle movement here, if the peddle was a pressure sensitive thing where there was a gauge you would see the slightest drop in throttle/acceleration and that is when it happens.

broken recirculating spring? Bad gasket in it?
i ordered a new recirculating valve last night so hopefully it gets here soon.

 

happened again today but i was able to see what i was hoping to see all along...
the wastegate actuator arm moving as the sound went away.
so... looks like the wastegate actuator is sticking open during a cold start.
is it hurting anything. probably not, short term.
is it a problem, yes...
taking it to the mini shop to get the turbo replaced under 3rd party extended warranty i have or turbo warranty which ever works.
the guy at the shop watched the video and thought it may have been the Aux air pump but looked and the N18 doesnt have one.
either way getting fixed,

 

Omg this is so frustrating. I guess my eyes and brain are F’ing with me because it did it again and I had a flashlight with me and the stupid actuator arm didn’t move a single inch as the sound went away.
today though right before the sound went away... the damn thing made the swoosh sound like the recirculating valve opened up after getting on it. Friggin crazy and this was the car idling.
then.. strangely enough, the car ran like a raped ape, more power than ever, just ridiculous I was loving it and didn’t want to shut the car off!

the recirculating valve is getting replaced tomorrow, so if that ain’t it, I give up. It must be the turbo or some vacuum issue.? but the only thing that would make that loud of a sucking sound would be the wastegate or recirculating valve being stuck open. my money is on the Recirc Valve.
well at least i finally get to install the BOV i got

 

Recirculating valve seemed fine? Maybe a bit stiffer than the new style I put n, even using the Alta spring.

dropped the down pipe and the waste gate is flopping around like mad! No wonder I been having issues.

 

At least you found the problem. I was following but also confused.

 

Confused because I was using this as a diary and the minute I found something it turned out not to be it.. or at least only part of it?

i added a downpipe, and new recirc valve . The old valve was stiffer but nothing I did would make it stick and it was clean from what I saw.
but the wastegate on the turbo,, jeez, like old grandmas ******* just flopping around in the breeze, it a wonder it works.
ok it ain’t that bad but it matches YouTube videos of bad wastegates