Gauge/Sensor Probelm ??? Great oil pressure on start up (40-60 PSI) but as car heats up, gauge SAYS pressure is dropping below 20 PSI. Dip stick says plenty of oil and filter is brand new. No knocking from valves either. Anyone dealt with this before? Thanks! - Al
Those Jeep sending units are not known to last forever. I would replace it (it a cheap part), OR you can always add a mechanical gauge to it and see what is really going on. In any case as long as you have at least 10 psi for every 1000 RPM you should be fine. So at idle you should have at least 10-15 PSI…
I’m just throwing my $0.02 in here, mainly because I have a '79 CJ7 so there are differences. I also have had an issue with my oil pressure dropping after warm up. Start ups great (30-50PSI for me) and then once I come to a stop at a stop light or turn off the engine and restart relatively soon my pressure would be way lower (20PSI and lower). One thing I did that made a drastic change was replaced my oil pressure relief spring. That pretty well corrected my lower pressure problems.
With yours being a 2001 though, I doubt it is a worn out spring. But it might be worth checking if you can’t figure out a better solution.
Thanks guys. Great ideas. I will start cheap and work my way up.
The oil pressure will normally drop as the oil warms and thins and as the engine warms. Oil pressure is created by the pump pushing the oil through the thin spaces between the bearings and their corresponding surfaces. That creates a pressurized fluid barrier for the wear surfaces to ride on. But as the oil thins, and as the spaces get larger from the engine heating up, the oil flows through easier and less oressure develops.
ASccording to my information, the factory specs 13psi minimum for a warm 4.0L Keep engine at idle. 20 psi is fine.