Hi,

My 2000 XJ had low oil pressure - got a check guages light came on and pressure would go to nearly zero on idle. Had it looked at and seems better now, but still idles at 10 psi, around 40-60 when driving around town. The mechanic said maybe bearings need to be replaced? Sorry my tech knowledge is a bit ****e, which is why I am asking y'all experts on here. He put 'heavier' oil in as said there was sludge in there and that may help pressure. I know manual says 13 psi is normal hot idle. is 10 bad?

any advice, as ever, appreciated

 

He said there was alot of sludge so the previous owner neglected regulasr oil changes or ran cheap oil and you may have some exsessive wear causing a lower psi. Running a thicker oil can make things worse. You do not have good oil flow when the oil is cold, so no oil to critical areas.
A 5-30 oil and a 10-30 oil have almost the same flow when hot, you gain by having the 5 wght oil at startup.

 

Are you using any coolant? Engine ever been overheated?

The reason I'm asking is that the 2000 has the "infamous" 0331 cylinder head, which is susceptible to cracking between cylinders 3-4. If it cracks, coolant starts mixing with the oil, which destroys the engine bearings and you see low oil pressure. A cracked head is always a possibility whenever I see an 00-01 with low oil pressure.

But I always verify low oil pressure. Don't completely trust your gauge. Get a mechanical gauge (some parts stores will rent this tool to you) and temporarily screw it in where the oil pressure sending unit resides.

Good data = good decisions

If you truly have 10 psi and the cracked head issue isn't in play, I've seen a lot of 4.0 engines run for tens of thousands of miles with 10 psi.

Spec oil pressure for the 4.0 is as follows:

*Not less than 13 psi at hot idle
*Between 37-75 psi over 1600 rpms

Let us know what you find out!

 

Thanks for that. I did ask about the head and he said it was fine as far as he could tell - no coolant leak. Checked radiator and no oil in there either. Temp always runs around 200, maybe 210 if going up a lot of hills. Drives fine since I got it back, but just wondered how you would raise idle psi to 13?

 

You should be fine, you could try a new oil sending unit, other than that I don't see any issue with your xj.Just so you know this and anyone who reads this(the coolant will mix with the oil (in the pan) the oil won't mixing into the coolant) so your mechanic needs to check the oil for sign's of coolant ,and not coolant for oil. Where they crack is between cylinder #3&4, pop off oil fill cap and look straight down for a crack that is green in color unless you have water in your cooling system instead of coolant.One more thing get a new mechanic he's already made two simple mistake's that any kidnergarden mechanic would know not to do.

 

thats good advice - thank you. he was at a jeep dealer, time to move on.

anyone know of a good jeep mechanic in LA?

 

I have a 99 Jeep GC.......just had this same problem happen. Oil pressure went low at idle.....and resumed 40 psi when gassed. I assumed I had Oil Pressure because there were no engine rattles and it seemed to run fine.
It was my oil Pressure switch!!! Haven't seen the problem since. $40 fix.

 

I recently had a similar issue with my '98. Very low pressure which often wouldn't come up at speed. Engine sounded fine and the way I drive it (mostly highway), I'd have blown it up already if it were low for real. Replaced the sending unit (easy fix) and now have great pressure, which I suspected all along.

 

I did the same and now pressure seems much better. just over 10 psi when idle. around 50 when driving. all seems good.

i also asked the mechanic i had been using about coolant in engine and he said that was checked and no sign of any.

 

I had the same simptoms (about 13 PSI at hot idle) and my PSI went up to 22-25 after replacing the o-rings in the oil filter assembly, which were leaking pretty bad.

I posted another threa to let others know...

 

Mine is 10 psi at idle with 0-30 in it hot. and almost 60 anything above 1000 rpm's

 

Make sure you're not running orange oil filters.

http://minimopar.knizefamily.net/oil...inions.htmlers.

 

pressure has held over last couple of weeks and did a long run over the weekend just to run out the engine a bit. all went well, that XJ really loves a good long drive. almost got nicked by CHP too for opening her up a bit too much...


what i have noticed is a small oil leak. just a few drops a day. had a look underneath but to my non mechanical eyes all looked pretty good and no obvious things. any suggestions? trying to avoid another mechanics bill if possible...

 

Crawl under it with a flashlight. Take a photo or two and post it up for us.

Here's where I would look first:
At the back of the valve cover, and anywhere near the oil filter.

 

So i had a look, and hopefully 2 pics attached to this? Seems to be one spot where the drip is forming. Does anyone know what this is?