Depressing making this thread...but none-the-less.

2000 XJ, 141k miles on the 4.0..ive owned it for 3 weeks.

The fella that "built" it I know fairly well...ive bought a jeep from him before...good honest guy. He sold it to a high school friend of mine from whom I purchsed it from. Before purchasing it I called the "builder" and asked him what he thought of the jeep...said the entire time he owned it the jeep always had a bottom end "knock". Said he installed a new HP oil pump and drove it thousands of miles with the knock.

I purchsed it, oil pressure has been constant at 15-20ish at idle..and 40psi at around 2000 RPM, it tops out at around 45-50psi at 3k+ rpm..ive probably put a thousand miles on it in 3 weeks..issue free.

Started it this afternoon let it warm up, headed to work..I look up at a red light and notice the check gauges light is on...and the oil pressure is all the way at 0. No extra knock (none more so than it already had)..with gas the pressure goes right back up to the 25-40 range dependent on RPM.

Pulled in the gas station to get a drink..came back out..same thing, no extra knocks...just 0 pressure and increases with idle.

I changed the oil last week with Rotella T6 5w40 oil and a mopar filter.


Im guessing im looking at cam bearings..?

I know nothing as far as engine mechanics..I know I need to verify the pressure...but just gathering thoughts.

--Dave

 

If it doesn't sound different then I wouldn't be to worried about it.Its problly just a issue with the sending unit or gauge.

 

Im gonna go outside on my lunch break and see if the oil looks milky...thinking maybe the 0331 head has cracked and is leaking coolant into the oil and thinning it.

Harbor freight sells a mech gauge for 20 bucks so I may go pick that up

 

Take the oil fill cap off and look in the engine with a flash light while it's running. You can see the oil and its movement. If it's flowing then you probably have oil pressure and like previously stated just need a sending unit. I was on my way to an off road event when my oil pressure gauge went to zero. Called a mechanic friend of mine and that is what he had me do. Mine was flowing fine so I stopped at a parts store and got a sending unit, been fine ever since.

 

1. verify first
2. look inside oil cap. If oil is flowing you are getting lubrication
3. possible cam bearings....common on 2000
4. Pressure at idle is not that important (if oil is circulating as I said in #2) as long as pressure returns....this is a sign of a tired engine.

FYI I have a 2000 that has been like that for the last +50,000 miles

 

I just went outside on my lunch, cranked it, looked at the oil on the dipstick...looks normal (not milky). Let it idle for 10 minutes...it got to 190 (which has always been the peak of temp for this XJ)..the pressure hung at 15-20ish.
I pulled hte cap off and there was definately oil up top...but Im in a parking garage with the led on my phone so it was hard to tell how much and if it was flowing..but there was def some up there.

 

All the bearings affect oil pressure, not just the cam bearings. Just because you have flow up top doesn't mean everything is hunky-dory down where oil pressure really matters.

A knocking 2000 XJ, 0331 head, suddenly 0 oil pressure at idle--limping along with thick oil and a high pressure pump--

Well, I think we know what's next.

 

Not to hijack but this is very similar to mine, I have a 2000 with low (10-13psi) oil pressure at idle, had cracked head and had a knocking noise which I seem to have cured with different oil. I guess I dont understand why everyone has stories of these being "bulletproof" yet you have given the OP the same death sentence as you gave me? I am not saying you are not right, I am just asking are these things not as "bulletproof" as everyone says?

 

4.0 engines are known for longevity. Unfortunately there a couple years that are known for cracked heads, which if ignored greatly decreases the longevity. Assuming proper maintenance, and quickly catching a cracked 0331 head you should still have a bulletproof ride.

 

10-13 PSI at idle is much better than 0.

The 0331 head is just poison. It has cost owners megabucks and megaheadaches. Many a fine Jeep has had to be scrapped because the owner that got caught with a bad head could not afford to fix it. Those heads have ruined many an engine on the lower end if not caught quickly.

As shown on this Forum, there are quite a few people that have bought a Jeep that was patched-up just enough to get it out of the previous owner's yard or off the lot.

A simple oil change will not fix a cracked head and bad bearings, or get to the root cause of a true engine knock.

 

No one can tell you with certainty how long your engine will last.
1. you may not have a cracked head...I don't and have been running foryears with lower pressure than you(20psi at highway speed).
2. If oil is getting to top of head you can bet your bottom dollar it is getting every where else unless you have a plugged galley.
3. Low pressure at idle simply means oil is FLOWING out of bearings faster than the low speed pump can build pressure.

I am a old man with 60 years of experience and have seen engines run for years with low pressure at idle. It is the nature of high mileage and wear. BUT bearing wear can be accumulative, if all bearings and lifter bores have only .0005 wear the engine will still be within factory specs but the oil pressure will be drastically reduced at hot idle speed. In the old days cars had idiot lights instead of gauges,these lights would come on at 2 or 3 psi and it was not unusual to see them come on when coming to a stop,yet they ran many more miles.
The point I'm trying to make is: There are only two choices to make.
You either rebuild or live with it until you have to.

 

There is a third choice: Bail out of it and sell it now while you can.

 

....and make that someone else's problem who will post a similar post and get a similar advice, and this goes around and around....


Just drive it .....

 

Obsession will drive you to the nut house!

 

Are there any guides or posts for guys like the OP and myself who may need to rebuild or replace an engine at some point? I know there are a million rebuilt engines you can buy but not sure if they can be all used in the 2000 / 2001 models that we have?