Hi

Yesterday I was pulling the wife's 2000 XJ 4.0 out of the garage to go visit my parents, something caught my attention on the gauge cluster: "CHECK GAUGES"
basically no oil pressure was present on the gauge, press the accel pedal and reached 2500 RPM and the needle basically hit about 5-10 psi, no good! This Jeep used to keep oil pressure at 25-30 at running temp/idle and a bit more while cold

Shut it off, open the hood:
oil level is OK
last oil change was about 1700 miles
no knocking
open the valve cover oil fill plug, and watched while running at idle, not too much oil present (wish it was a lot more), riched in with my finger, and no evidence of recent oil, just like it was shut off for sometime.

So I'm pretty sure the oil pressure went to zero or close to it as there is no visible evidence of oil getting to the head

possible causes in less cathastrofic order:
-clogged oil filter (it is not a FRAM) just in case, also not a WIX or Mopar as we do not get those down here
-clogged pick up tube/screen on the oil pump
-failure on the oil pump itself / relieve valve
-weared oil pump gear drive (not sure of the correct name, but whathever get the pump to turn from the camshaft)
-bearing damage (this is for obvious reasons the less desired scenario I can think off, and honestly the one I think is less likely as the pressure dropped from one day to the other)

Are there any other possible causes you can list, I need to tackle this in the correct order to discard things and find the real cause, this will be a job for the weekend (hopefully) as during the week I'm busy at work at day/college at night

thanks to all

 

You said no knocking so its got oil pressure,If it didn't it would sound like someone beating on your front door trying to come in!
Check your oil pressure with mechanical gauge just to make sure tho.

And this must be the day of dieing 2000-2001 xjs.lots of post about problems with them today.

 

I will say no nocking yet, pretty sure I got the issue at the very beggining and did not drive outside of the garage, will get a mechanical gauge before any dismantling!!!

thanks

 

When the senders fail on these, they usually fail exactly the way you described. So while you could actually have an oil pressure issue, you may just have a bad sender. This is why you need a mechanical gauge to make sure you're not chasing a problem you don't have.

Harbor Freight has a nice mechanical oil pressure gauge for $25 (less with the ubiquitous 20% off coupon). It has a six foot hose so you can drape it over to the driver's side and see it while sitting in the truck, just in case you need to shut if off quickly. You'll have to take your sender out and install the mechanical gauge in its place, but that takes less than 5 minutes.

If the mechanical gauge shows good pressure, replace the sender. This is one place where you can waste time and money going with the cheaper aftermarket options that read incorrectly or just fail again in three months. Go to the dealership and pay the extra for a real Mopar sender.

It's not just today. A number of new people have bought '00 and '01 XJs recently and found their way here to learn just what they've gotten themselves into. I have noticed a LOT of them for sale on Craigslist lately, so it looks like they have reached that age.

 

This guy knows what's up.
I skipped the mechanical gauge and went straight to replacing the sending unit. Miraculously my oil pump started working again . . .

 

Those gauges are only there for people who are not gear heads to ask questions .. Basically a way for dealerships to make money and charge you for diagnostic time

 

Update

Bought a cheap mechanical oil pressure gauge, we have no HF here so I found a cheap mechanical with a tiny plastic tube in between the oil filter base and the gauge itself.

Started the XJ without any modification, still 0 on the cluster, and slightly moving when reving.

Removed the oil pressure sender (which broke while removing it), and put on place the mechanical gauge, started the Jeep, 50 PSI at idle being cold, and a little more if reving.

Eventhough the mechanical gauge is so cheap, I think it will not be off more than 20 PSI, so I should be on the good side, with at least 30 PSI at idle cold.

Next step, a new sender, I will also have this mechanical gauge tested on my other XJ that has a working oil pressure sender and will compare the PSI readings.

Thanks to all, will try to get pictures uploaded

 

Yep, you're fine. Get the best quality sending unit available where you are. Do not get the cheapest.

 

Yep, and it bears repeating. Go to the dealership and get a Mopar sender. I've never been a huge fan of overpriced dealer parts, but this is one place where the extra expense is worth it.