Hello, I have a 1994 z28, a4. Was passing a slow car and when i stopped at a stop sign my check gauges light came on and oil pressure went to zero. I put a mechanical gauge on it and it confirmed the factory gauge. When engine is cranked oil pressure is around 50 psi and it is not until it gets hot that the oil pressure drops but will increase if the rpms increase. Engine is still strong, makes no noises, and doesn't smoke even though it has 130k miles on it. I have also noticed that the gauge needle starts jumping around a bit on it's way to zero. I always ran 5w 30 castrol with ac delco or k&n filter. I have also tried changing to a 10w 40 castrol with the same results. Do yall think it is worth changing the oil pump and shaft or do yall think it is definitely bearings? Any ideas would be greatly appreciated...thanks David

 

I had the same problem. The "knock" sound started a couple weeks later.

I had spun a rod bearing.

 

side note, it's most likely not the oil pump. They're mechanical and pretty solid. If the pickup tube has come out, you can verify this by draining the oil and hitting the oil pan with a rubber mallet. If you hear the pickup bouncing in the pan, then it has fallen out. Aside from that, you have probably lost pressure due to a spun bearing.

 

I would check the oil pressure sender and wiring first to see if it's in good working order.

 

He put a mechanical gauge on it.

 

....

 

Do you think the mechanical gage can not register below a certain level? Like say 20PSI? Reason is if you truly had zero pressure, it would most likely lock up or throw a rod. Since you still get pressure and still drive it, I highly doubt it's truly zero. 15 maybe like my L31 at hot idle but not zero.

 

I knocked on bottom of oil pan when I changed the oil and didn't hear anything rattling around.

 

Oh and have not been driving. If it is bearings don't want to do any more damage that's already been done.