I just bought my 2000 Cherokee 1000 miles ago. It has 96k on it. Im already having problems. I changed the about 600 miles ago with Castrol GTX 10w-30 and a Fram filter.
Since the oil change i have been having this problem. For example. Today i was made a 20 miles interstate trip. Everything was fine on the interstate. 80mph, 195 temp, and 30 pounds of oil pressure. When i get off the interstate a hit a few lights. About the third light the temp starts to rise to 210. Then it makes it to 220. You can almost watch it get hot at a stop light. Once it gets to 220 oil pressure suddenly drops from 10 to 0 and the check gauges light comes on. Once i get back on the gas oil pressure goes back up to about 20. Stop at another light same thing. Back to 0. This is with the A/c on and like 100 degrees out side in Florida.
I switched my oil back to 10w-30 mobil 1 with the mobil extended performance oil filter. Same overheating and oil pressure problem. I replaced the oil pressure sensor. Same ****. The Jeep has plenty on coolant and oil. Also has a new water pump and temperature sensor.
Any ideas as to whats going on here? It never has a oil pressure problem untill it gets to 220. Then its like a switch..bam zero oil pressure. Maybe the radiator? Fans?

 

When your temp starts to go toward 220* does the Aux. Fan come on?. The XJ likes to run at about 210*, however the fan should come on after that. If not this could be your problem!

 

I need to check on the fan. I haven't really listened for it. That would explain it getting hot. But, the main thing that's concerning me is watching that oil pressure gauge hit zero. A new oil pump maybe? Is the oil just getting that thin because of it being hot outside and the engine being at 220?

 

you have a 0331 head..(google it) .....well known for cracking and letting coolant slowly seep into the oil. over time/miles it will wear out the bearings causing low oil pressure.

First thing to do is verify with mechanical gauge the oil pressure to see if it is as low as gauge cluster is reading.
Also have you had to add any coolant? is the overflow bottle staying at the same mark and not getting lower ?

Possible the PO had the head replaced but bearing damage was already done when you bought it?

 

When i first bought it i noticed the coolant was about half a gallon low. I filled up the coolant and it hasn't lowered in 1000 miles.
Im not sure about the head being replaced. It doesn't look new. I did notice the throttle cable mounting bracket on the valve cover is missing its nuts. That kinda scares me. The previous owner did replace the water pump shortly before i bought it.

 

If i have 10 pound of oil pressure with the a/c on at 210 degrees is that bad?

 

all seems normal - i got a new jasper and engine seems to like 210-225- with new water pump- i would not worry about it

 

with my ac on it runs 210 - 225- its normal

 

Dont be a wimp just shut of the a/c at the stop lights and get rid of that fram oil filter before it comes apart on the inside and plugs up the screen.