[M117 and M119] Timing chain replacement?
 

To replace or not to replace? I know there has been much discussion of V8 timing chains in a number of threads, but I would nevertheless welcome any comments and suggestions on my particular case (or, rather, two cases in fact).

My M117 and M119 V8s have on them, respectively, 241k km (149k mls) and 165k km (102k mls). Judging by what I have read on this and numerous other forums, the common view is that the timing chain and its ancillaries on these old V8s should be replaced around the 100k mile / 160kkm mark. I have asked my MB garage (a large very well equipped facility with people having great technical knowledge and experience of MBs, which I have been using since more than twelve years to service my cars) whether the chains should be replaced and they said a definite ‘NO – there is no need in these two cases’ (they have known these two cars for, respectively, six and four years now and I can safely say that they are more than familiar with both specimens).

The chain stretch in both of these engines is ZERO degrees. Both cars have full service histories, but there is no indication of the chain being replaced in either. Is it possible for a chain with more than 150k miles in the M117 to have no (measureable) stretch at all? Or is this likely an indication that it has at some point been replaced in the past? I have had these cars for a good number of years now, but have only covered 16kkm in the 126 and 13kkm in the 140.

Neither of the cars show any indication of any chain rattle or any other worrying timing-related sumptoms.

Should the chains, tensioners and guides REALLY be replaced at this point in time or, as indeed suggested by the aforementioned MB garage, there is in fact no need to do so.

I remain baffled.

I had over 250,000 miles on my 400E with the M119 and never had an issue with the chain. My E420 probably has over 200,000 miles as well. Recently, just for peace of mind, I pulled the valve covers, pinned the exhaust cam sprocket with a drill bit and replaced the chain tensioner and upper chain guides, which were completely intact but brittle. My only regret was that I didn't use factory valve cover gaskets and now the passenger bank is slightly leaking at the front.

I'm curious how they checked for stretch. Did they remove the belt tensioner?

I think that the guides are more of an issue than the chain itself. They tend to get quite brittle with age and heat. I know that a special tool exists to feed a new chain into the M119 by linking it to the old one, (thereby making it relatively easy to replace the chain), I don't think it is factory however. I think it was custom made and a few copies were made. Not much help, I know...

The folks on *********.com have a lot of 119 and 117 experience.

Rgds,
Chris W.
'95 E300D, 368K with original chain