Ball bearings in my oil screen!
 

Hello,
I posted this under a different post but now have a more specific question. Where could the 12 small, 3mm, ball bearings which I found in my '79 300td oil pump strainer have come from? There is also a part of their retainer in there. The size of the retainer would point to the bearing belonging to a shaft around 3/8"' in diameter.

The vacuum pump has been suggested. Any other ideas of how ball bearings got into my engine oil?

The vacuum pump is the only part in the engine with ball bearings.

Nice to have cool, experienced heads on this forum. If I found ball bearings in my oil I would freak!