All of this thread is very enlightening and kudo's to all who have offered insight into this ....dear I say it...rare condition..
I find this very interesting. For why ? The 240/300D Mercedes 4/5 cylinder engines use a chain to drive the oil pump as does the V8 116 and 117 series engines, among others....as well as the cam/s.
Never seen an oil pump chain fail...apart from one that eat a piece of metal and jammed.
These commonly run 300K and a 240D I just took of the road had logged 720,000 miles.
Perhaps VW should have stayed with the T1 engine design and stuck with Porsche's gear drive in the first place..
But having said that...the boxster engine is having similar problems with it's balance shaft.
Note: There are no chains driving anything in aircraft engines...apart from Wilber's that is. Here's a little write up I found interesting.
http://www.epi-eng.com/propeller_reduction_technology/chain_drive_issues.htm Note the comments about chain life and temperature.