Not familiar with the 190D but if it is anything like my 300D, I had the exact same thing happen to me on Friday. It turned out to be the air cleaner bracket broke. Need a little more info regarding your rattle.....Did the rattle change intensity or frequency with changes in engine speed? Did it do it both in and out of gear? I would cautiously start it and look for anything loose that could be rattling. If it was severe enough to do damage I would think it would have done it within the mile or so you drove it home. But just the same be ready to shut it off if need be.

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2012 Mercedes ML350 Bluetec 102K (hers)
2005 Corvette 55K (fun car)
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1998 Volvo S70 T5 Turbo 211K (kids)
1994 Ford F150 4WD 246K (firewood hauler)
1983 Mercedes 300D 384K (diesel commuter)