Mechanical failure - Tensioner pulley.

Towed in (roll-back) to MB dealer as a precaution due to crank pulley history as pointed out by Len Sokoloff and others. Repaired, back home safe and sound, compliments of Mr. StarMark.
:-)

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https://goo.gl/photos/J8ZUVvAYiYqLxbD18

1989 560SL 111Kmi
2007 E550 4Matic 157 Kmi
2000 F250SD 7.3l, 1996 Explorer Ltd 5.0l
1965 VW Beetle Deluxe 115 Kmi
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Previous MB:
1983 240D Euro Manual 144 Kmi
1983 300SD 495 Kmi
1986 190D 2.5 100 Kmi
1986 300SDL 202 Kmi
1991 300D 2.5 Turbo 91 Kmi
1998 E320S4 (4-matic wagon) 140 Kmi