SORRY TO DRAG UP AN OLD THREAD!!
Had my 320i for around 6 months now, only has 17000 on the clock and this is the issue that i am having. When i turn the car on from say sitting over night, when the car's revs are between around 1.5k-2.5 it sounds like a tractor/diesel. It can be heard even when the car is just revved. Which can be seen at around the 30 second mark. I was worried it may be a loose bearing or something but it actually disappears after driving the car for around 5 mins i.e when the engine started to get hot. Really starting to get worried and not exactly sure what bmw are gonna do if they actually can do there jobs and accept that there is an issue here. I will be showing them the video because no doubt they wont find fault when they take it out.