Kpdub

Hey guys, I've been browsing the forum for months, but just now joined in an attempt to gather some more information. I bought a 2000 XJ sport about 6 weeks ago. Automatic, 6cyl, 4x4. The XJ is all stock with 160k miles on it. About 3 weeks ago I noticed the oil pressure was getting rather low at operating temperature (lower than 10 PSI, but not 0 PSI). I changed the oil, oil filter, and the sending unit. Now, once my engine temp reaches 210 degrees and I'm at idle, the oil PSI immediately drops to 0 and the warning light displays on the dash. If I give it some gas and raise the RPMs, the PSI will begin to climb back up. Could it be as simple as changing the pump? Or am I looking at something bigger? Bearings? gaskets? Etc

00t444e

Could be a bad sending unit, you need to test oil pressure with a mechanical gauge, also what oil and filter did you use?

dave1123

Your in the wrong section of the forum, but luckily I'm well acquainted with this common XJ problem. The first thing to do is use a mechanical gauge to verify your actual oil pressure. According to Jeep, as long as you have 13 psi at idle hot and it rises above 1000 rpm, it's within specs. Scarey, I know, right? Anything less can be either worn bearings or a worn pump. The oil pressure sensor can be reading wrong if the pressure shows okay with the mechanical gauge. It's common for it to get wacked with a filter wrench when changing the filter and start to leak. If you replace it, it's recommended to use an OE part.

I bought a very neglected 2000 XJ with only 125K miles on it and it had about 5 psi at idle hot. I bought a sensor from a dealer and then had 15 psi at idle. Not satisfied with that, I switched to Shell Rotella 5W-40 Synthetic Diesel Oil and it raised the idle pressure to 25 psi. That I could live with. I even tried removing the oil filter adapter and screwing a slightly smaller filter directly into the block ,and it didn't change a thing.

I believe engine compartment temperature has a lot to do with the low oil pressure and overheating problems with this model jeep. Case in point, I have 50 psi on cold startup, 40 psi at driving speeds, and 35 psi at idle when the engine just gets to operating temp. It drops to 25 at idle after the engine heat soaks. It will stay at 30 psi if the outside air temp is around 30-35 degrees. It has been mentioned by several people that the XJ body was designed for the 2.5L 4-popper and then they decided to shoehorn the 4.0L into it, leaving not enough room for adequate airflow for cooling. Experience seems to prove this because installing hood louvers helps cool it.