Timing chain stretch - opinions?

[cornblatt]

Since my car is approaching 200,000 miles, I thought it would be a good idea to inspect the timing chain to make sure it's not excessively stretched or worn. The car is a 1984 190D 2.2 with the 4-cylinder OM601 engine.

I followed the procedure shown at http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain_TSB.pdf (thanks for posting this document!)

It was fairly straightforward, however since I've never done this before, I thought I would post the pictures and see if anyone who has experience with this agrees with what I saw...

First, I lined up the marks on the camshaft sprocket and camshaft bearing cap:


Then, I inspected the timing mark on the crankshaft pulley (see photo below). It's rusty and hard to read, but to me, it looks like the needle points 3° away from the "OT" mark.



I don't know what I'm doing , but from the diagrams in the instruction document, I kind of expected the needle to be on the other side of the "OT" mark (since that's the view they showed in the document). Do my pictures look right?

To me, it looks like 3° of stretch. The reason I question my results is that the timing chain was checked at the dealership around 30000 miles ago, and they reported "0.1 degrees" of stretch, which I consider to be surprisingly precise after going through the procedure myself. I can't picture how someone could measure fractions of a degree of stretch, so I am thinking that they must have made a mistake. Having the chain stretch by only 0.1 degree in the first 170000 miles and then 3 degrees in the past 30000 also seems unusual.

So, if my 3 degree measurement is correct, then according to the document, I guess I need to replace the chain soon. Do I replace the tensioner too?

Thanks for your help!

[leathermang]

I know nothing about your particular model engine....
but yes, even in the shop manual MB expects the most wear to happen in the first part of a chains' life... not to start wearing more per mile later on....
I too am skeptical about measureing to .1 of a degree....

If your tensioner is the same age as the chain I would sure change it...

Does MB supply offset keys for the cam sprocket to correct ( up to ) a certain amount of chain stretch.... as it does for the 616,617 engines ? MUCH easier to do that if all other stuff is ok....