David,

I am not real sure exactly what the sequence of events was, but I think it goes something like the following:

When the mount was actually broke in half, I witnessed the engine trying to start using the starter, and it would lift about an inch or more on the driver's side mount and bang back down as the starter turned the engine over. I did not go over to the other side of the car and look to see where the starter might be going to see if it was hitting anything. There is an "L" shaped bracket on the forward side of the starter that is fastened to the block using 17mm nuts, and some rinky dink screws to the forward cap on the starter. These screws were broken off when I took the starter out, so I am guessing some of the jumping around caused the starter to either hit an adjacent component, or after a few months of this activity, it just fatigued the screws and they broke. When I got the starter out the three cylindrical modules it is made of were loose, meaning they would rotated and wiggle quite a bit, but they did not fall apart into three pieces.

It is entirely possible the mounts had nothing to do with the demise of the starter, but having witnessed the beating about the motor went through trying to start at the end, I am leaning toward either over loading the starter structure due to out of phase torque pulsations from the compression of the engine as it turns, and the lifting of the engine and then dropping it back onto the broken mount as the starter was turning. I did not notice any damage to the starter like dents or other deformation from hard contact with the other components residing under the hood, so I am not attributing the failure to hard contact. Then again, it could have been just old and ready to die. The unit I removed was a rebuilt starter, by the way, provided by Mercedes-Benz to the previous owner some time before 1991.

I think the two failures are related, but can not prove it with the data I have and do not feel like running an experiment by putting the broken mount back in and seeing how long it takes to break the new starter. If someone has a better explanation, I am all ears. The car likes its new pieces and is running great again. And thanks for the guidance when I started the job, as without that "virtual experience" I might have given up and junked it. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)