I just did a quick search on the MB archives over at the MB mailing list and found this:

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My observations on the 103 engine timing chain are based on what I asked my shop, the Mercedes Service Center.....The owner said "Not to worry about it". I would consider them to be experts.

And despite your assertions that the 103 engine "won't make 300K miles" there are already a number of them with 200-250K miles without major work done.

I think the following observations are in order in re: timing chain life

1. Different engines have different designs & length of travel.

2. A few engines had a single row design making timing chain life a major consideration.

3. If changing were that critical, this would be in a DBAG recommended maintenance procedure.

4. If doing something such as a valve job, it would be foolish NOT to change the chain, since you're 3/4's there.

I agree with your remark about the experts...However if we all relied only on "experts" input this would be a rather quiet list. I would number the people I've known on this list as "experts" over the years as < 10...I of course do not consider myself among that group.

Should you change a chain based on mileage? On some models the question is more relevant than others. If my 300E had 175K miles I would consider it. One certainly can't harm a vehicle by over-zealous maintenance...

Certainly your remarks about relative cost of a chain vs an engine overhaul are correct - who would disagree with that?

I stand by my assertion...

Bill
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Basically, I wouldn't worry about it unless you're having work done in that area.

~~Paul