So I have a 2004 E320 wagon which is great. I wish I were still driving my 95 E320 with the amazing mileage and smooth six but had to get something newer and a bit larger. And it had a slight groan sound slowing down and starting up just above idle.

Sounds like a power steering or AC pump or the serpentine idler or something up front at the radiator area..It could POSSIBLY just be the plastic engine cover vibrating at this RPM..It stops when the idle drops to a nice stable 600 or so and its very smooth above 1100 on driving but has this groan area on slowdown and speed-up.

I dont see many comments on the w211's but this extensive chat about the SBC brakes letter which I just received is interesting. The valve replacement has already been done and it should be good! This was among my priority concerns on this car. Seems I need not have worried about this issue since MB is covering these systems now in full. Fingers crossed on the air suspension!

Thanks for any comments if anyone has similar experience..Just turned 104K miles and I have been driving since 85K on the odometer..

Check your power steering fluid level.

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CENSORED due to not family friendly words

Thanks and yes, it was a tad low and I sucked out the old fluid and renewed it with fresh and increased the level a bit. I will keep an eye on it!