I purchased my E320 in May of this year with 80k miles. This being the only MB I have ever owned I thought it was kind of loud so I started by replacing the idler and tensioner pulleys. It was still quite noisy. Yesterday (at 96k miles) I was in Atlanta and decided to visit with Webmaster and Benzmac. I had Benzmac take a look at it and he told me it was the alternator bearing making the noise. I did not have him replace it at that time because I figured I could do it myself this weekend. Now the interesting part - I never drive this car in traffic like what is found around I285 and I85 in Atlanta. I got into a line of cars on I285 southbound that were going 0-20 mph for MILES. Anyway, the radio ant. went down the radio turned off and the digital display went off of the radio. Every now and then it would come back on. I continue on in this kind of traffic and the radio keeps doing this crazy thing. Finally the car started bucking real bad and would not accelerate worth a flip. After thinking about it for awhile I realized that I always drive on clear roads where the rpm only drops below 2000 when I am coming to a stop so the alt. keeps charging. Once I got into the heavy traffic it became quite clear that I needed a new alternator. Try to make sure that it ain't the alt. before you rule it out.
good luck
engatwork
'95 E320
'97 Honda CRV