Yes the max these engines run at is 215-225 (dont quote me) so the oil gets pretty toasty. And i dont know much about grand cherokees enough to know if they have different sender types and such. but like many others say if you wanna know your true temp.... put a mechanical gauge on it cause these have inaccurate gauges majority of the times. and if it is true then stick thicker oil in. overheating in most cases causes your oil to degrade thus wearing out bearings and such, Also having coolant in your oil is bad too if you have a blown headgasket and ran in it. And like i say feel free to let the wizards correct me lol

 

Good point, the zj and xj certainly have different cooling setups....xj has the small clutch fan plus the electric fan, and the zj has the one large clutch fan. I think I will put the scan tool on each and see which runs hotter.

 

I think the major problem with XJs is underhood venting. I recently parked and waited for my sister to go shopping and decided to check the oil while I was waiting. I opened the hood after about 5 minutes and the heat hit me like I opened an oven door! After only about 30 seconds with the hood open, I was able to reach in and pull the stick. I think putting louvers in the hood would be a great idea....if only we could figure an easy way to funnel rainwater away from the engine. Maybe even drilling large holes in the firewall into the cowl area would help. I noticed when I stop and leave it idling, then open the driver's door, it's quite toasty on my legs as I get out. It's not so bad with my WJ.

 

It does get hot under there! I ran for a year or so with my hood raised 1/2" clear across in the rear. Didn't seem to make a bit of difference temp wise but it sure got dirty under there from the dust (which turned to mud when it rained) from our unpaved roads. Even watched leaves and other debris ride the windshield down and through the gap. Got the lowered now.

 

Yeah, we used to put 1/2" blocks under the hood hinges when we drag raced for the same reason. Only problem was if you blew a plastic oil pressure gauge line, the windshield got covered with oil!

 

So the XJ runs hot idle at 203F, per the CTS reporting to the pcm....still have to check the ZJ, but the gauge does look lower on the zj....

 

Hi everyone,

I have the check engine light on and it seems that it is check gauges. Pls see attached.
I am planning on changing the oil pressure sensor but Im not sure if that will solve the issue.
Any idea what this might be?

 

Not the oil pressure, that looks great. Wasting money on a new sender.
That engine light doesn't look like a 'check gauges' light. That looks like you have codes stored. The check gauges light says 'check gauges'.

 

I have to change everything I've said about that stupid banjo bolt! I've removed the adapter and using a smaller filter, screwed it directly into the block. IT DIDN'T CHANGE A THING! My idle oil pressure is still the same. It seems oil temperature is the main cause of low oil pressure in XJs. When my engine just reaches operating temp, idle pressure is 40 psi, but after it's run for a while longer, it slowly drops until it gets to 25 psi. Extreme venting of the engine compartment or an oil cooler will help this, but IDK how a cooler will be good in the winter. The XJ body was designed for the 4 cylinder or the small V6, THEN they crammed the 4.0L into it, even modifying the firewall for clearance to make it fit! There is no room for the airflow needed for cooling.

Oz E, that's a Grand Cherokee (WJ) your riding in. You can check your trouble codes by turning the key on, off, on, off, on and wait. The trouble codes will appear in the odometer one after another, then display "done".

 

**Sniffs his coffee, takes a sip, and thinks, I see what you mean!
You sure have some interesting inputs on Chrysler's evolution of the xj and the 4.0. Sort of a historian! Me thinks, how he knows all that stuff, where would one find that out? But..sounds believable to me.

The spec on the xj, from memory, is that it runs around 210. Mine fully hot, (with oil pressure dipping to around 18) runs around 205 per the CTS scan tool. Within spec, but, I do think the zj runs cooler than that with essentially the same engine.
Tinkering with the idea of running some straight 30W oil in mine to see if it makes a difference. The elephant in the room is that conventional wisdom dictates low oil pressure is worn bearings, likely rod bearings.

 

Oil cooler might not be the greatest idea, unless it is a fancy one cooled via the radiator. Having both the oil and the coolant heat and cool at the same rate should be the better route. Not sure where to plumb in an oil temp gauge, but that might be a good experiment before adding an oil cooler.

 

I'll bet nobody knows the XJs suspension was designed by the chief engineer of the Renault Formula 1 racing team either, did you? HA!

Go to jeep.com/history.html

 

25 psi at idle isn't bad at all.

 

That is what I keep thinking every time I click on this thread.
I'm getting 22ish psi at a very hot idle.
On an '00 with the 0331 head.
Very happy with my oil pressure.
You have this head on your Jeep you have a tendency to keep a close eye on things. LOL.

 

Yeah, tell me about it! After cracking one on my WJ, I constantly keep an eye on things. Plus after many years driving other peoples junk, anything less than 40 psi at any time is scarey.