My Theory:

1.) The belt probably had a small crack or tear that you never noticed,
or which you felt was negligible.

2.) The person driving the car ran the engine at high RPM for an
extended period -- say 60 seconds.

3.) The belt disintegrated.


Premise of Theory:

This is what happened to me in my 260E. The belt had a small
tear -- like somone took a toenail clipper and snipped a small piece from
the edge. One fine evening, for reasons unknown, I felt compelled to shift
into second gear while driving down a small hill. The engine revved to about
5000 rpm and, seconds later, the belt flew apart, causing all dash lights to
come on.

I was less than a mile from home, so after pulling over, shutting down, and
then restarting (to make sure I could) I drove home. The coolant
temperature began to rise rapidly and by the time I got home it was in the
red. When I opened the hood I saw the shredded remnants of the belt, and
the coolant in the reservoir was boiling.

You should probably have another chat with the person who was driving, to
find out what really happened. How hard were they driving the
car/revving the engine? Did they not think something was seriously wrong
when the entire dashboard lit up after the belt was gone? Etc.

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
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