Low oil pressure after vehicle is hot, but no noises.
I have just purchased a 2002 Dodge Durango. When we purchased all seemed to be ok. Until we got it home. Of course the dealer told us they had gone all through the vehicle and it was in great condition. The deal started the vehicle right away so we didn't check the oil. On way home noticed once truck was warm from trip the low pressure seemed a little low so the next morning I checked the oil it was Black and almost 2 quarts low. Took it in and had an oil change. But oil pressure is still doing the same thing. The manual states that anywhere in the range is normal oil pressure, but I do not understand why it starts at 3/4 of range and once hot it drops to 1/4 range. I have no noises, she runs very quiet. Not sure where to start to make sure it is not something that is going to cost me major down the road. Anyone have any advice. It would be greatly appreciated.
You should have a oil pressure test done to make sure but since not tapping may just be a bad sensor that screws into the engine block that goes the the oil pressure gauge.
What you're describing sounds pretty normal to me. Oil pressures are always higher when the engine is cold because the oil is thicker. When the engine and the oil warm up the oil thins out some so the pressure drops some. For example, my '03 S-10 pick up truck starts cold with the oil pressure around 60 PSI (sometimes 80 PSI in the bitter cold winter) which is about 3/4 on the gauge. Once warmed up it stays around 30 PSI which is about 1/4 on the gauge. So I think you're ok. HTH. -Jim
BTW those pressure figures are at idle speed. -Jim
Well last night on way home it dropped to the line right at the edge of low and it didn't leave there most of the way home. It has proper oil level. After it had cooled I started it again and now it starts at only half way on gauge instead of at 3/4. It is getting worse, but it still hasn't dropped low enough to have any bells or light for warning of low oil pressure. I have been tol oil pressure sensor, oil pump, leak which it is not loosing any oil, and oil screen sludge or wore internal parts. How can I find out for sure which is the actual cause. I know the sensor can be tested with a pressure test and the screen, the pan can be dropped, but how do I know if it is the oil pump or wore out internal parts without tearing the whole motor down?
For testing purposes you can hook up a mechanical oil pressure gauge. That'll tell you if the gauge on the dash is accurate. If it's not then I'd suspect the sending unit is bad or the gauge itself is bad. However if you find out the dash gauge is accurate and you have high mileage you can suspect worn crankshaft bearings, worn oil pump, sludge, or a worn pressure relief valve. HTH. -Jim
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