This timing chain problem with the 420/560 discussed herein has far too many instances for anyone to have found the true cause and it seems endemic to this engine design. (I have a 76 MBenz that has over a million miles with the same time chain;
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I don't recall ever seeing any posts on this site saying that the chain broke. It is always the plastic parts that cause the problem. That being said, why would MB design an engine using plastic in the timing system? This is a huge problem just waiting to happen. I grew up driving and racing GM vehicles and never saw a timing chain problem on any street car. Only at the drag strip with highly modified V-8 engines did chain failure ever occur. When I begin driving MBs I was told about the 10 year/100,000 mile rule. I couldn't believe what I was hearing. Again, why would any car manufacturer design an engine with plastic parts in the timing system?

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1986 560 SEL (159K miles)