[bassfreak]

Oil pressure sensors are somewhat antiquated devices. They were actually used to alert drivers to possible low oil levels. When the oil level was low, the pressure usually dropped. It is very rare for the oil pump or its drive chain to fail on these engines. If it were to fail, you'd likely not be able to save anything even if you were monitoring the oil pressure. I've not actually heard of a single failure like this, ever.

Failure of pump assembly can also be caused by other issues, aside from chain or pump drive..
Have you seen this one on the M113K engine?

Also there's an issue with this kind of O-ring for the M272 engine, and it makes itself heard as the rattling noise on startup after car stands for more than ~5hrs:

- check the comments to get to the O-ring issue diagnosed in the russian forum.