I had the same identical problem with my 2000 XJ when I bought it. The PO had just replaced the oil pump and the oil pressure sensor and this is why he decided to sell it. It had 30 psi on cold startup and 10 psi idling hot, only 20 psi at driving speeds. I did the oil filter adapter cheanout and seal change, bought a Mopar oil pressure sensor which cost me $78, switched to a Purolator One oil filter and Shell Rotella T6 5W-40 synthetic diesel oil. Not she holds 45 psi on cold startup, 30-35 idling hot, and 40 going down the road. This jeep only has 130K miles on it in 19 years and is whistle clean internally. I believe the major problem with these engines is the restriction caused by the banjo bolt in the adapter. You should also clean out the passages in the elbow that the pressure sensor screws into.

This same engine in my 2000 WJ had the new "clean side" block where the oil filter screws directly into the side of the block, not into an adapter. With 253K miles on it, idling oil pressure is still 40 psi hot. It runs 55 psi at 60 mph. Same oil and filter.

You don't clean anything up? And you throw your new o-ring on the dirt?


I don't have a nice concrete surface to work on like many of you do. Like that kid, I work on a gravel driveway. It's a pain. But I do manage to keep my new parts out of the dirt.

Same deal on my new-to-me 2002 WJ. I have been wondering why it runs 60 going down the road. I suspect it's full of Lucas. First oil change should be interesting....

The thing that I find interesting was when I went to the dealer to buy the oil sensor, the one for the 2.5L was only $34 and the one for the 4.0L was $78. IDK what the difference would be. I found this out after the counter guy had already wrung me up, then another guy came out and said "Wait! You gave him the wrong one!"

He probably gave you the oil pressure switch meant for the dash with an idiot light instead of the gauge.

It might be. It only had 1 wire whereas mine had 2. When the oil pressure sensor in my WJ started leaking, I bought a new one from the dealer and when I took the old one out, it broke in half. There's a printed circuit and a crystal inside it, not just a diaphragm and resistor like the old ones. According to wjjeeps.com after 02 the oil sensor is just a switch that sends a 40 psi signal to the gauge regardless of the actual oil pressure. I asked a dealer salesman why they didn't just change to an idiot light and he said "Chrysler cars always had a full set of gauges. People don't like idiot lights."

On the XJ, it really doesn't matter much but with any of the later models that have the data buss system, all the sensor data is sent to the PCM which decides what signal to send to the gauges. No direct connection from the sensors to the gauges.

awg had a good tip where he used 2 wrenches together.

Yeah but he had to buy 2 wrenches of the same brand to get them to line up. I think he said HF. When my mechanic did mine, he BENT a Snap-On! He cut the hex bit short and hammered it back into the socket to give him room to get a ratchet on it. There's barely enough bit sticking out of the socket to fit the bolt now. But now I own it!

BTW, it's 12mm, not 1/2".

Well, after having gone through the list of low oil pressure checks I still get all the same readings. Oil pressure looks fine for about 10 minutes or so and then I get about 10@idle and 20@acceleration. Any thoughts out there about a next move? Here's a comprehensive list:
- Replace cracked head
- Oil pressure tested mechanically to confirm gauge is working properly
- Sealed oil pan
- New oil pump
- Inspected crankshaft
- Inspected camshaft
- Cleaned banjo bolt at oil filter
- New WIX oil filter
- Replaced oil pressure sending unit
- Cleaned out elbow that the oil pressure sending unit
- Using 20w 50 oil
- No visible oil leaks
- Coolant level holds steady

????? Thanks everybody!

You lose a majority of your oil pressure in the cam bearings so “inspecting the cam” was nothing but a waste of time and money honestly . To fix low oil pressure you’re going to have to swap or rebuild because youre likely losing most of it in the cam bearings . Your mechanic should of never suggested an oil pump either that’s just silly . Anyways 10 at idle is enough to get you by and 20 while driving for possible another 100k id just drive it til it blows ! Personally .

I'd consider slapping in a high volume oil pump.

Just drive it and don't worry about it, maybe look for a spare engine in the meantime.