Trouble with oil pressure

When I first start the car and the engine is cold, it idles with a pressure of 40 on the gauge. When the car warms up, the oil pressure drops below the red line when it is idling, and goes back up when I get on the gas. Has anyone had this problem, and what have you done to fix it. Thanks :)

I have the same problem with mine. My cousin told me it probably was the crankshaft wearing out, the shaft has holes drilled in it to lube the bearings and the pressure drops as the holes get larger and the oil gets warmer, flowing easier. I don't know if this is actually true, or if he was pulling my leg but I have been driving mine this way for the last 3 years without any problems but that doesn't mean you won't. The only hassle I have with it is that the chime goes off when it drops. I think it is probably the oil pressure sensor or sending unit, but I am definitely no expert and I would like to know how much of what I know is correct. I am sorry I could not offer you any cure to your problem.

This does happen with older engines as the pump wears and clearances get greater. You may see an improvement if you increase the weight of the oil say from a 5w30 to a 10w40. If it keeps getting worse you may want to replace the oil pump as this should correct the problem.

Bigboyisme, what you said sounds similar to what I was told by someone else. I took the car to a dealer where one of my buddies works at, and he had the engine guy look at it. He told me that the main bearing was scored, and that the oil was leaking through that way. GTP Dad, I originally thought the oil pump might be bad, but I've also been told that oil pumps don't go out very often. Do you have any thoughts about what the mechanic told me. Does that sound like a plausible problem? Also, I think the car is already using 10w30 oil.

bigboyisme, does your engine start tapping when the oil pressure drops in your car? And does the water temp do up? It also seems like the more I drive it with the problem, the worse the performance gets, and the lower the pressure gets, even when I get on the gas. I've stopped driving it all together.

It is possible that the main bearings are going out but I would suspect that if the engine is not making noise that the oil pump is going bad first. I had a friend with a 327 that the oil rings were stuck on that caused the oil pressure to drop to zero, the engine finally went bad and he had to replace it. I also had a friend with a Chevy Corsica with a 2.8. He was driving along and the oil light came on. Engine locked up, cause--Oil pump failed. Had only 60K miles. Rivendale, you didn't say how many miles were on this engine or what size it is. I had a 2.8L that had over 200000 miles on and maintained 60 psi when cold and 40 when idling hot. What the mechanic told you is probably true but you may be able to save the engine by spending a few dollars to replace the oil pump. If it is worn your oil pressure may be restored with a new one. The first thing I would try would be to change the oil pressure sending unit. Cheapest part. If that doesn't work then change the pump. Finally if that doesn't work explore rebuilding or replacing the engine. That may be your only recourse at this point.

The car is a 1995 Bonneville SSEI supercharged. It has 88000 miles on it. Really the only noise it makes is a tapping when the oil pressure goes to nothing. Other than that, the car runs, and rides great. I'm not real familiar with newer car engines, but I think it's a 3800

3.8l

the oil pump creates flow, pressure is created by squeezing that flow thru the small passages in the engine. I would guess you have some bearings(either rod, main or cam) that have excessive clearances. The integral oil pumps in the 3800 engines have been known to wear out, causing oil to bleed past not creating flow, which would lead to low pressure also. I would check a sample of your oil and see if there is any indication of metallic particles in it. IF there is, you got bearing problems, if not, the oil pump is probably worn out and needs to be rebuilt.

Richtazz, I think you might have hit the nail right on the head. I went back to the Dealership today, and he explained pretty much the same thing you just said about the bearings. I also noticed today that the engine clatters alot when it is hot. The mechanic said that is the sound of the bearings clattering from the excessive clearance. I would also like to know more about the "Integral oil pumps" you were talking about. Does that mean that they are built into the engine, and not a separate component that can be taken off and replaced?

If you hear tapping noises you need to shut it down and fix it. That oil pump is probably shot, It is common for them to go out.

The oil pump is built into the timing case which is on the front of the engine but behind all the accesrories, belts and brackets and junk. Not fun.The oil pump on that engine runs off the crankshaft.When you get the timing case off,you'll see tetth in the hole where the crank goes through.Thats the pump gear.I hope your engine isn't smoked.And I would check the pickup screen in the oilpan to be sure its clear.If you ran the engine too much, there's a good chance an oilpump won't help now even though that might have been the first problem. If you can,I would take a look at a couple rod and main bearings first.Check them with plastigage and if the clearances are beyond .003 an oilpump probably won't help.I would check the rear rods and mains.They seem to get the most wear.Depending on how long you've been driving it chances are a motor change will fix it.Make sure you change and check the oil on time. Good luck .

I appreciate everybody's help. I took the car to the dealership today, and my contact is going to do the work on the car. He is going to open the engine and grind the crankshaft, and replace the main bearing, and the rod bearings. He said because of the miles on the car (88,000), I might need a new timing chain, but maybe not. He said the oil pressure is created by the pump pushing the oil through the small spaces in the engine. He said If the bearings have worn and created excessive clearance, then there is more room for the oil to go, and less oil pressure is maintained. When the engine is cold, the oil is thicker and doesn't move through the bigger openings as easy as when it is hot, thereby creating a lower oil pressure when it's hot. The engine also rattles when it is hot, also leading him to believe it is the bearings. I will ask him to look at the oil pump while he has it apart since it has been alot of people first choice of problem. He did say that he thinks the oil pump is ok since it does still create pressure when I get on the gas. I would appreciate any additional info anyone could give me.

Sorry I didn't get back to you, I lost the thread for a while. I don't have any problems with noise coming from my engine at all. I don't have any knocking issues either, knock on wood.
I just get the pressure guage going down, and warning beeps, as the oil temp increases. No engine overheating or anything like that. I would like to know where the oil pressure sending unit is located though. Does anyone know where it is?
I also have another problem lately. I recently replaced my plenum gasket set on my car and it seems to have stopped the stumbling problems I had, but now my car is hard to keep running when it is started cold, it also doesn't want to accelerate until it warms up either. Any good ideas as to what might be causing that?
I checked my fuel injectors recently, they are working fine, checked and cleaned the EGR and throttle body, replaced the air filter, changed the oil and filter. Don't know what's up.