Should I replace M103 chain since head is off?
 

Should I replace the chain at 90k miles. I don't see much if any slack at all....but I have a brand new chain with the guide....

I have the head off and its sitting there until I get it back from the machine shop. In the mean time should I replace it for good measure seeing as I have a new one or leave it alone?

How long do you think it should take me from here?

You may not want to change the chain, but you sure do want to reset the tensioner...

As Arthur said....Chain tensioner needs removed and reset. Personally I would, although I have seem them go 200,000 or more.

With the head off it is a real easy job. ...as is the guide.
HOWEVER...after I did my own, I now have a slight whirring noise at idle.

I have re chained about 60 or 70 Mercedes over the years...perhaps more, but never got this noise from a 103 engine before.


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I have both the chain and guide. I understand the guide is the cause of the chain going bad. Should I just replace the guide and reset the tensioner? Or just do it all?

I wouldn't on an M103, maybe at 250k do the rails

Took a good look at the chain today...It looks perfectly fine....but look at this guide (tensioner guide = name?)

http://www.ps2cho.net/downloads/phot...hain_guide.jpg

Replace or is this normal?

If you already have the timing chain cover removed, I would change the rails. It was a bit of a pain to get mine removed. At almost 200K, mine did not look bad but if you are in there already........

If you look at the old files,
 

I replaced the guides on my car the last time I did the head gasket. You need to removed the front engine cover. Be ready to use a breaker bar to remove some parts. Do a search. I am glad I did. The guides are plastic and mine where crumbling in my hands when I took them out. Add an extra day to you current repair job.