I purchased a 2009 ML320 BlueTec 5 years ago with ~10,000 miles on it, and have driven the vehicle an additional 125,000 miles now. I have had 3 items fail that were not warranty items, an AddBlue tank heater replacement, an A/C controller and recently a glow plug control modules. Not bad. Mechanically very reliable and I get great mileage driving in and around Boulder, Colorado - averaging over 27 mpg over the 125,000 miles and routinely get over 30 mpg on the highway. I attribute the higher than expected highway mileage to the lower air pressure/air density at a mile above sea level as a trip to Indianapolis a few years ago gave me some experience at more "normal" air pressures and the mileage suffered a noticeable drop.

Anyway, I am very pleased with the car so far, although the engineer who designed the air cleaner arrangement deserves several years of therapy to overcome his or her disdain for customers who like to work on their cars, and mechanics in general.

I have had a vibration problem though. At 70,000 miles my first encounter was ultimately repaired under warranty. The problem was a bit of a conundrum as I was told my description of the vibration was not unique but no mechanics had been able to duplicate the problem and inspection of the drive train had shown nothing unusual. MB had taken to replacing much of the front half of the drivetrain (this is clearly where the vibration comes from) to no avail.

So, the problem occurred when the car was under a light, steady load driving up a hill at 55 mph to 60 mph, and the road was somewhat rippled. The front suspension/drive line would begin a resonant response to the excitation frequency of the road ripples and if I maintained the same engine loading, the response quickly grew exponentially in amplitude. It was quite alarming.

The only way to stop it was to either give it a lot of throttle (not likely in traffic) or severely reduce the throttle input (also not a friendly thing to do in traffic). I checked the tire balance several times and then took the car to the dealer to have it examined. I got the story - the mechanic could not repeat the issue and they had tried replacing most of the drive train parts to no avail. So I took the mechanic at the dealership for a ride. Took two passes at the hill where this happened most frequently, and when it started the mechanic got his iPhone out to record the events. He asked to give it another try, but I could not get to the right speed in traffic. A long story shortened slightly - it turned out to be a "carrier bearing" on the front axle with too much play. The bearing was replaced and the problem went away, for another 65,000 miles. It is back.

I was wondering if anyone else has experienced a similar vibration/resonant response issue.

Thanks for reading through this if you did,

Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)

Any vibration issues I have had in the R320 were directly related to tires/wheels and balancing. Some could not be balanced no matter what, others got uneven tread wear and now shake. Nothing with the drivetrain yet, similar miles.
Our other car a 15 year Jetta, lots of problems tracking down a vibration and really just not worth worrying about anymore, I understand it can be tough though!

At the end of the line of suspects, there's always the possibility of a loose or worn bearing.