Not sure where exaclty the noise is coming from. Sounds like it's coming from the front driver side of the motor. It only happens when the car is cold and it will go away after a few minutes or when I start driving and I won't hear it until the car sits and get "cold". I haven't found a video of a vaccume pump failure making this noise, So I'm hoping it's not that. If anyone has any advice that would be great. As soon as I got the noise on video it went away on it's own. It's a ra-ra-ra-ra sound.

Watch "Strange sound. 2011 MCS" on YouTube

 

Open the hood and listen.. it may sound more like a 'tap-tap-tap' in succession.. like an annoying drummer on a high-hat. *Mines doing the same. Ive been monitoring all the vitals from the OBDII so far.. no issues. I still dont like it though. Im going to get a video and send in to my dealer to see if its enough to cover warranty replacement.

*fingers xssd

 

I just got the video to upload with the post. Not not sure if it's the pump or what. Wish my car still had a warranty ha. What numbers are you exaclty looking in via OBDII?

 

I have an N14.. not certain if the Vac pump is the same.. but it IS in the same location. That is what you touched in the video. Could be yours just makes a different noise, with your dual-vanos setup on the N18 (still ..sounds a bit rough though for sure). Mine has same behavior, just different noise.. still not a good one, lol.

*Im checking vacuum via OBD. While it should go '+' under boost.. it would read low at idle. A vacuum issue would also affect the wastegate ..as its vacuum controlled too pretty sure.

 

If your vacuum pump fails and locks up it kills your engine since it runs off the exhaust camshaft. It's an easy repair, just make sure you have a magnetic socket so the bolts don't fall out of the socket. Another tip is to put a shop rag under the vacuum pump to catch the bolts if they fall.

 

yeah I know about the vacuum pump and how it works, just not sure if this is a common noise on one that's "acting up". In the video i touched it not to see if that was the pump but to see if I could feel anything since I was able to catch the noise (finally) on video while it was happening. I didn't feel anything weird and when I put my head close to it i couldnt say "yup, it's the pump". Just baffles me.

 

Well today I was bleeding the coolant system and I got another strange noise from the car. The car sat all night so I topped off the coolant opened the bleeder screw got a nice stream of coolant coming out put the cat back on the reservoir start of the car with heat on high fan speed on low and just let the car idle until I got up to temperature. I went in the house to do a few things in 20 minutes later come back out check on things and when I come out I was hearing this God awful screeching sound. Sounds like it's coming back by the throttle body that's where the noise gets really loud at. Not sure if it's a belt or pulley the water pumps less than a year old, friction wheel less than a year old, new pulley on the friction wheel and a new belt when I did all that. the only thing that's not new is the belt tensioner. I can't think of anything back there that would cause this type of sound unless there's a crack in the intake I don't think that would do it.I'm not for sure anyone have any ideas? As soon as you touch the throttle noise went away completely why I'm kind of thinking it might be belt or pulley related.

Watch "Belt maybe?" on YouTube

 

Heard something similar from another car I owned and it proved to be an accessory drive idler roller bearing.

If you are going to try to diagnose noises a mechanic's stethoscope is pretty useful as it lets you test various areas/items and determine from where the noise is coming.

In the case I mentioned above the problem was besides a couple of idler rollers there was a tensioner roller bearing and some accessory drives like water pump, power steering, A/C compressor and alternator. The tech used a stethoscope to pinpoint the source of the noise.

 

I wish it was a idler pully. I mean it could be a tensioner or a.c. pully but the sound come from the back of the motor not towards the front so I'm not thinking it'll be those. Since I replaced the cold aide boost tubes to get rid of the noise maker I wonder if I don't have a good seal around the throttle body. But I'm not sure if I'd get that kinda noise from air being sucked through a loose coupler into the throttle body.