BK2001XJ

I've had this problem pretty much since I got my 2001 XJ. Its got the 4.0, 4 wheel drive, automatic, 4 door. 149k miles. So far I have done some major work to it to try and fix this. The oil pressure drops down to 0psi at a hot idle and the "check gauges" light comes on. Whether I put it in park in a parking lot and leave it running or just waiting too long at a stop light, it happens. I'm very confused at this point. I've put in a new sending unit, rod bearings and a few other bearings in my engine and an oil pump. I've done other miscellaneous jobs in my engine unrelated to the oil pressure. It's weird because driving down the road, I have fine oil pressure, depending on where the rpms are its always 15-40psi while driving. But for some reason its when it idles for too long. And it never happens cold, only after the engine has reached NOT. Some body help! I'm really lost at this point.

Big David

I had a issue with low oil pressure in a TJ I used to own. I swapped out the Fram oil filter & all was good. Do you use Wix filters? If not, you really should.

BK2001XJ

Mopar made the oil filter

Turbo X_J

If the clearance was actually big enough that the connecting rod bearings needed replacement the cam bearings are toast.

BlueRidgeMark

Before you go crazy with replaceing and rebuiling things, get a mechanical gauge and see what you really have.

You can probably rent a good test gauge from Autozone or Advanced (for free), and check it.

Or do like I did - buy a mechanical gauge and just temporarily hook it up and take some readings. Mine was showing similar signs on the built-in gauge, but the mechanical gauge said I had 40 pounds at idle and 60 at 2100 RPM.

Cost me a whopping 17 bucks. Works for me.

SeriousOffroad

Bad cam bearings.

BK2001XJ

Ill do that Monday and get back to you on it. hopefully its the same thing you had going on.

extrashaky

Harbor Freight has a decent mechanical oil pressure kit for $25, or $20 with one of their 20% off coupons.

The elephant in the room nobody has mentioned is that you have a 2001. Does it still have the original 0331 head? If so, you may have the dreaded 0331 head crack that has allowed coolant to get into your oil and eat the cam bearings. If your oil pressure tests low with a mechanical gauge, you may want to have your oil tested for the presence of water/coolant before you go throwing any more money at it ($25 at Blackstone).

BK2001XJ

Thanks for the tip. I really hope that isn't it. but if it is I better get to it as soon as I can.

bigbadon

Look at the manufacture date on your engine. I bet it is 2000. There were issues with cam bearings walking or spinning out of their bores. Look closely at your drained oil change for shiny specks. Now maybe the good news....mine has survived for over 5 years with 0 psi at idle and 20 psi at speed.

BlueRidgeMark

I doubt it. Put a mechanical gauge on it and see what it really has.

bigbadon

Done that 5 years ago! @ 650 rpm it reads 3 to 4 psi. On a really hot day pulling a 3500# trailer it barely moves off the peg from zero when I come to a stop.

BK2001XJ

Checked it with a mechanical gauge and I couldn't get it to go below 15 psi. guess I got nothing to worry about. Also my sender was pretty loose so maybe thatll help it out some

BK2001XJ

Update: I changed my oil and along with 5 quarts of Castrol GTX 10W-30, a K&N Oil Filter and I put in Lucas Oil Engine Stabilizer that takes place of one quart of oil. And now the gauge in my dash always reads 50psi while driving and never goes below 10psi at a hot idle. I believe it fixed whatever my issue was. The stabilizer I think just thickens the oil and theres also many other additive that contribute to helping the engine run better. Another thing I was contemplating doing was changing my oil with 15W-40. Any input?

BlueRidgeMark

15w-40 is a good idea. Shell Rotella or Chevron Delo. These are diesel oils that are very well matched to these engines. You can read up on it here.


The Lucas is NOT a good idea. Just gunks things up and masks problems.

If you can't maintain proper pressure with a good oil, and you are sure your engine is basically shot, something like Lucas can get you a bit more mileage until your engine completely dies, but other than that, it's doing more harm than good.

Remember, your goal isn't high oil pressure, it's a properly lubricated engine. Lucas will give you a good reading, and starve your engine for oil.