I'm looking at a 2006 C230 with the M272 engine with 170,000 miles on it and I've heard this engine has a problem with the balance shaft gears. Somewhere it was mentioned it would fail at about 70,000 miles, could I assume that it's ok now? I'm thinking either it was already fixed or it's not a problem with this engine, that is if it hasn't failed by now it's not going to.

I just took it for a test drive and the engine seems a little rough for a six cylinder, but i'm used to my smooth as silk in line six M103. It almost seems like the balance shaft was removed. Is this normal for this engine?

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5 speed '91 190E 2.6 320,000 mi. (new car, fast, smooth as silk six, couldn't find any more Peugeots)
5 speed '85 Peugeot 505 2.5l Turbo Diesel 266,000 mi. (old car, fast for a diesel, had 2 others)
5 speed '01 Jetta V6 (new wifes car, pretty quick)
5 speed '85 Peugeot 505 2.2l Turbo Gas 197,000 mi. (wifes car, faster, sadly gone just short of 200k )
5 speed '83 Yamaha 750 Maxim 14,000 mi. (fastest)
0 speed 4' x 8' 1800 lb Harbor Freight utility trailer (only as fast as what's pulling it)