Hey all! first of all i would like to introduce myself: my name is Eli and i'm from israel. i drive a 2006 C200 CDI with 225K miles. the car is great but there is something that bothers me. for the last 6 months i have a strange rattling noise in about 2500rpm. i hear it the most when the transmission changes gear at about 2500rpm (the car is automatic). when the car reaches 2500rpm, i hear noise li "tr tr tr tr tr" - very fast. at first i thougt it might be the transmission but the noise is there even on praking or neutral. my father is a mercedes mechanic but even he's not sure about the noise souce. he also thought theat it might be the manifold shutters but it works fine. i tried to run the car without the engine belt for half a minute and the noise gone, so he now suspects it might be the air-con compressor. is it possible that he's making that kind of noise? does anyone heard of same issue before? the noise is there but it doesn't appear to influence on anything - the car runs perfectly. i tried to find similar noise on the internet but i didn't. try to imagine someone drumming very quickly on a tin can. thank you for your help!