I stupidly decided to do some maintenance on my 2005 R53, which was running perfectly. I changed the oil on the supercharger so I had to take apart the front end. When I put it all back, I had issues with the coolant, not bleeding it, and the car overheated. After that, I thought I had properly bled the coolant system but when I took it out for a test drive, it started whistling, loudly. At first it took a few minutes of running the engine for the whistle to start but now it just whistles all the time, and there is coolant leaking under the engine. The car is not overheating at this point but I am not running it too long.
I don't see and bubbles when I check the oil, but I do see some light smoke when I open the coolant reservoir.
I have included a youtube link of a video of the car whistling:
Thanks in advance.

 

Does the whistling stop when you remove the coolant tank cap. If it not then the only other place that can produce a whistle sound is the intake. Check intercooler seals, the throttle body, BCV. vaccum hoses.

 

It keeps whistling with the coolant tank cap off. Thanks.

 

You have a vacuum hose off somewhere. Check the two red connections on the intake plastic elbow.

 

Thanks, I'll check that out.