When I get in my C220 CDI (w203) it drives fine until the engine worms up (10mins) and then when I either accelerate or brake there is a noise from the front of the car that sound like a broken fan. When I take my foot of the peddle it goes away until I accelerate or brake again. The sound reminds me of when you used to put a lollypop stick on the back tyre of your bike to make it wound like a motobike. Sorry for the last sentence but I can not think of another way to describe the noise so I hope you know what I mean.