Car: 2008 E350 with later M272 Engine.

For the past three weeks I noticed an increasingly severe oil leak in the front-right corner of the engine. Upon closer inspection, and after a costly "repair" by a shop that misdiagnosed it as the oil pressure sensor, I saw that he leak was coming from behind the alternator. The only thing there is the timing chain tensioner.

After reading how-to's and watching instructional videos, I decided to do the repair myself. What shocked me was that the tensioner was so loose that I could unscrew it by hand!

Is this a common fault??

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black