During my last warranty visit to the dealer they replaced the engine idler pulley. They indicated that it required replacement, however, I did not notice anything that was wrong. Since replacement, I now notice that there is a bearing noise that sings to me when the engine is operating over 2000 RPM. If I let off of the accelerator when doing highway speeds and engine speed of 2500 RPM the noise goes away as it would when you unload a bearing. Parking it in the garage and increasing engine speed while in "Park" shows the bearing noise is coming from the area of the idler pulley. I am thinking that the part is defective or they did not do a correct installation.

All I can say is that these new Mercedes are not like the old. Between my 2000 ML320 and my wife's 2003 C230K I am visiting the dealer 2-3 times per month on average. It will be extremely difficult for me to consider purchase of another new MB. By the way I also own a 1995 Mercedes C280 which hardly ever causes any issues and will definitely be a "keeper."