W126 Timing Chain
Just got a call from MBI Motors in Portland (independent shop that came highly recommended). I asked them to take a look at the timing chain on my 160,000 mile 500SEL. The owner said the timing chain was stretched (never been changed), the guides had lots of cracks, and the tensioner needed to be replaced.
I guess I was VERY lucky!!
He said that the radiator neck had been shortened and I should replace the radiator. I asked that he reinstall the old one and I would start looking for a used one.