The cause of my Low oil pressure

My '94 Firebird has low oil pressure. On a cold start the pressure will be a 20 psi, but it will decrease as the car heats up, and eventually floor at idle. The car has a relatively rapid oil pan leak. Oil drips rapidly when the car is on, but the oil never goes low enough for the oil light to come on. Could the leaky oil pan be the cause of the low pressure? I’m about to replace it, so I’m hoping that will end the problem, but I’m not sure if it could be something else(oil pump)

Well you haven’t told us some important information like the mileage or the motor your car has, but I’ll try and answer your question. First off, in regard to whether low oil pressure is caused by a leaky oil pan the answer is no-period. If it’s leaky you need to replace the oil pan gasket-not the oil pan.

As for your problem I think you need to sit down and read some articles online on engine design and how they work, as you seem to be a bit lost as to what oil pressure is. Low oil pressure is the result of excessive clearance in the bearings of the engine, or possibly a failure to circulate oil properly. Factory gauges sometimes aren’t very accurate, so I usually prefer to see a reading with a real oil pressure gauge. However, let me ask you this: does the gauge needle move slowly upward or downward when you rev the engine?

I saw a diagnostic test for oil flow that gives a visual verification of the source of your problem. First off do a test of the oil pressure using a mechanical gauge with the engine cold and hot. If the pressure is indeed low, go ahead with your oil pan gasket replacement. In the mean time rig up a pot of oil that can be pressurized and flowed into the oil pressure pipe fitting. With the oil pan off pressurize the oil pot to about 20 psi and observe the oil flowing out. If it streams out of the main or rod bearings, you have too much clearance there. If it streams out of the oil pump, you have too much clearance in the pump. If the oil comes down from the cam shaft area, the cam bearings have too much clearance. This test makes a mess but it would save you from replacing the oil pump when the real problem is too much clearance in bearings.

Let us know how you implement this test, the problems faced, and the results you get.

The actual pan is rusted out.It leaks pretty fast when the car is on. I was told that a low pressure reading can be caused by low oil levels in the pan,and air gets in the pump. The car has 128,000 miles. When I rev the engine, the gauge moves slowly upward. It will completely drop to zero if I idle in Drive or reverse. If I’m in neutral, it will hang around 20psi. The engine is relatively quiet with no knocking or unusual bearing noises.No tapping.

My oil filter is also leaking a bit. Can this contribute?

I’d be very surprised if either leak had anything to do with the low oil pressure (assuming you confirm the oil pressure with a quality gauge). You describe what I’d expect for either a worn out engine, or possibly a worn out pump. Since you’ll have the pan off anyway, I’d check how much a pump would cost. I’m not one to throw parts at a problem, but if a pump’s not much money, it might be worth replacing it to see if it helps.

any more help out there? Anymore suggestions?

If the engine is full of oil and the pressure is low then odds are you have one of two problems. One is minor and the other is major.
One is a faulty oil pressure sending unit. If it has never been replaced you can try changing that and see what happens. It’s cheap and easy…
Two is the possibility of worn out crankshaft bearings. To verify this you would need to remove the oil pressure sending unit and install an external gauge. If the add-on gauge shows low oil pressure then you have a serious problem.
(Badly worn crankshaft main bearings can also cause to crankshaft to move excessively and wallow out the crankshaft oil seals. Maybe the rear main is the steady oil drip you see)