Low oil pressure

I own a 1998 Buick Park Avenue, although I love my car it has been a pain in the neck lately. The problem is low oil pressure. When I?m driving the car is all fine, when I?m going in reverse is all fine and when I?m parked is all fine too. Now, when I have been driving it for a bit and then hit a stop sign or a red light the low oil pressure light comes on. The gage says the pressure goes down to 5 psi, but then when I press on the accelerator the light goes away and the oil pressure goes up again. The engine doesn?t make any deadly noises, it doesn?t stall and it doesn?t run rough at all. What could this be?

Side note: recently I had the intake head gasket (or manifold) and the thermostat replaced.

What engine size and configuration is in this car? How many miles are on the engine? Was the intake manifold gasket(s)or head gasket(s) replaced because of loss of coolant into the engine? Was the engine oil changed along with gasket replacement? Has a mechanic connected a test gauge to the pressure tap? What was the reading at idle and 2000 RPM.

Until more information comes in, I would suspect worn bearings, a bad oil pump, or the pressure regulator valve stuck open.

Will keep an eye out for your response.

the engine is a V6 3.8L. It’s got almost 130,000 miles. Yes there was coolant leaking into the engine. Oil was changed. No i havent taken it back to the mechanic for a pressure test. But the car measures it at 5 PSI only when i stop.
Thanks so much in advance for the help I really appreciate it.

That engine is very strong and reliable. It usually outlasts the body. Timing chains and leaky intakes are the only weak links that I am aware of. If the oil were contaminated with timing gear debris or coolant it could damage the engine causing loss of oil pressure. It would certainly be advisable to get the pressure confirmed and if the gauge is correct inspect the crankshaft. There are .0001 undersized bearings available on that engine which can add many miles of service if installed before the crankshaft is damaged.

What weight oil are you using? Try 10/40 if you are using 5/20 or 10/30…

Many older, high-mileage engines suffer this affliction. You need 10 psi oil pressure per 1000 rpm engine speed.

Have someone test the ACTUAL oil pressure with a gauge. You can’t go by the dashboard read-out. If you’re lucky the pressure is OK, but the pressure sender may be faulty. A mechanic can measure the pressure and find out.

I would have hoped that the LIM (lower intake manifold gaskets) repair was before any serious damage was done to the bearings. I would suspect so since you report no lifter noises. Too low a pressure WILL ABSOLUTELY product hydraulic lifter noise at low engine speed.

While many suggest having the pressure checked with a mechanical gauge by a mechanic, the cost of the procedure is as much or more than swapping the sensor out. If the problem goes away, it was the sensor. If it doesn’t (999/1000 times) you do have a problem that will make that cost very minor.

Again, here you report no noises or anomalies that ALWAYS accompany truly too low oil pressure/flow due to worn bearing leakage.

ok guys thank you so much for the helpful information, but the problems with this car are far from over. I took it to the shop and it was the oil pump that went bad. I replaced it. The mechanic also told me the engine bearings were bad due to the fact that i drove the car with low oil pressure (it was only for about 4 days). Now the engine has a little noise when you listen to it from the outside, but when I drive it in the highway i can feel an awful lot of vibration. Should i try replacing the bearings or should i just ride it till it dies? Can i repalce it myself? I have done some work on this car before. Radiator hoses coils etc.