Here's what happens:

After the vehicle is warmed up (1-2 hours of driving OR 20 minutes on a 90 degree day), when I sit at idle, the oil pressure drops to 0 and the check gauges light comes on. When driving, the pressure picks up again to normal. No other lights come on, and the engine runs consistent when this happens.

Here's what I've had replaced so far to "fix" the problem:
Oil Pressure Gauge
Oil Pump & Shield Cleaned

I've spent about $650 so far trying to get this "fixed" and it still happens. It used to happen much more often, usually within 20 minutes of driving, but it has improved with these things being replaced. The engine was rebuilt less than a year ago, but I don't know how reliable the guy was that did it (previous owner).

Thoughts?

 

oil pressure sending unit.. might be your problem.

 

Put an oil pressure tester on it. I did mine this weekend (I was getting zero oil pressure at idle and about 10 PSI at 2500 RPM even when cold). Tester showed 45PSI cold at idle and about 38-40 when at operating temps. Replaced the oil pressure sender for $22 and now shows on dash exactly what the oil pressure tester showed.

Even with very limited mechanical knowledge you can do this yourself. Total time and cost for my fix: About $35 ($22 for new sending unit and $9.99 for the oil pressure tester). About an hour total under the hood, including time to get the Jeep up to operating temps (about 15 minutes at idle).

 

Hmmmm...I havea feeling this part was replaced as well, but not sure. I'll look into it-thanks! If it WAS 0 oil pressure, wouldn't the engine stall out or run rough?

 

Bearing clearances, especially the crankshaft bearings, expanding after warmup causing excessive clearance and drop in pressure.

Spun/scored bearing(s).

Try putting a mechanical gauge on it and pulling over and checking the idle pressure after warmup.

If it is good, you have a guage/sending unit problem.

If it is bad, see above.

 

Get one of these:

http://www.harborfreight.com/cpi/cta...emnumber=92687

Takes just a couple minutes to install (goes in place of the oil pressure sending unit). Check pressure at idle, if OK run Jeep until warmed up, check again. If still OK, drive (after tucking gauge in to a nice spot behind the washer fluid bottle) then check once more. If all are good then replace the sending unit. If not then be prepared for new motor or rebuild (as you already replaced the oil pump).

Hardest part of the above testing is finding the 1 1/8" wrench. Both my sets only went up to 1" box end wrenches, but thankfully I was able to borrow one from the machine shop at work.

And you are correct in that there usually will be some noise if you are really at zero oil pressure. Our 4.0 motors use hydraulic lifters and get very noisy if starved of oil. That is the general rule, but better to test and be sure than to wonder and be stuck on the side of the road somewhere because you figured everything was OK...

 

I have the exact same issue, including the prerequisite drive time required for the gauge to light.

Put in the order for a new sending unit today. I'll update this thread if that solves my problem.

JessieJeep, any updates from your side?

 

I had this issue going on with my 99 XJ so I disconnected and removed the oil pressure sending unit, the harness plug was full of wet oil, so I blew it out and cleaned up/dried the connections, and it works better then ever. Oil pressure is now reading about 50 on the guage. I might add this issue occurred right after I sprayed the engine block with degreaser (to find an oil leak), and it made its way in to the harness...just like it did at the neutral safety switch
If it happens again I'll drop the $25 for a new one...

 

It's a good idea to check the date on a thread before replying.

 

Hi!
I have a 2001 XJ sport 4.0 with 122k on it.
I get the check gauges light everytime I’m at a red light and when accelerating (30 psi) and at 2k rpms I’m at 20. It seems to hold around 7 then just drops.
I switched the sending unit for an oreilleys one and same thing. Put the old one back and it’s a little better.
my question is, isn’t there a oil pressure light? So if my gauge was actually correct the light would be on?
Hoping it’s not my bearings and crank shaft, as I’ve just finally gotten to the fun stuff.

 

 

OK it looks like no one has asked yet but here goes , What oil are you using ?