Hey folks. New guy here. Restoring a 1985 Cabby.
ISSUE: After driving for about 5 minutes the Oil Pressure bottoms out. I removed the oil pan and upgraded the Oil Pump with a higher volume pump from an early 90s 1.8L from Parts Place.
What I found when I dropped the pan was this: a handful of what appeared to be about 5/8" long fiberglass fibers. The oil pump pickup was choked badly by the fibers. I mean I don't see how the pump was really picking up anything.
I cleaned everything up and used the new high-volume pump and pickup assembly. The car did great for about 10 miles and we are back to almost the same problem. I have replaced the oil pressure sender in the head and in the block. The gauge in the console seems to be accurate. But now, low oil pressure again after 5 minutes. I am taking the valve cover off today and cleaning the oil return passages. The engine has extremely lil sludge. 150K miles.

The fibers came from a bad oil filter some time ago I believe. Any opinions?

Once the oil returns are clear of fibers, do I need to replace the sender in the head? Could the fibers be inside the sender and screwing it up? The low oil pressure only comes on after about 5 minutes of drive time. I am hoping that the oil is just not finding the oil pan quick enough. The fibers seem to be from what was then a poorly made premium filter. Maybe a Fram premium? No clue. Every time I am working on this car, I am replacing the oil and filter. 10-W30 Castrol HM Oil and Purolator One Filter...