Odd oil pressure revisited... again.
 

Hello, all. This would be my first post to this forum, though I have visited the archives frequently when I have needed answers in the past.

Anyway, not to beat a dead horse with more oil pressure questions, but I have a 1990 300SL that seems to have normal oil pressure, meaning 3 bar at idle or cruise when cold, 1-2 bar at hot idle, 3 at hot cruise. However, every once in a while I'll be accelerating on the freeway and the pressure will go from 3 bar to 0 instantly (red warning light, too). It usually jumps back to 3 within 5 seconds, but somtimes it takes longer... feels like an eternity! Also, slowing down helps the pressure recover faster. When I finally return to idle, the pressure reads the normal 1.5 bar, but the needle will never get beyond 2 bar even at 3000+ RPM. Usually, I'll just park it for the night.

Next day, everything will be back to normal, and may stay normal for weeks. There are no other symptoms... no increase in engine noise or temp, or loss of performance.

The engine will always rattle for about 2 seconds from a cold startup, though I've heard it's not necessarily a sign of pending engine death.

I would guess the pressure sender is getting weird, but setting up a mechanical guage to double check doesn't seem practical since I might be waiting a month for it to act up again. Any ideas are appreciated.

Sorry for such a long post.