0 oil pressure at idle when hot
 

I've done the research to find out that this could be the sign of a bad oil pressure sending unit, but ....it IS freaking me out....
Changed my VC gasket over the weekend, drained oil then added 5 qts of Rotella T6 (I left the filter alone because PO changed it approx. 6 wks ago, but I wanted to get the Rotella in there). I do need a new oil pan gasket, but the write-ups suggested that it is a little beyond my skill level at this point -- no drips, just a lot of seepage (related wildcard?).
Anyway, last 2 days here have been around 90 degrees and on my commute home, about 20 mins in when everything is really hot, my CHECK GAUGES light will come on when I come to a stop and the oil pressure (I understand that it is actually "flow") will drop to 0.
However, when I take off again, light goes out and gauge goes back to norm (although it has always been a tad below the suggested minimum 13 at idle since I've owned it). I have been watching it really closely since the gasket change -- no drips from gasket at all and no oil loss according to dipstick or driveway, although I was startled to look under fill cap and see that it looked dry to me (the top of the valve that I could readily see).
Another (potentially related wildcard?) ...I am concerned by how hot to touch the upper radiator hose gets (planning a separate thread and weekend of figuring that biz out).

ADVICE, CONCERNS? I'm not sure if all/any of these activities are related or if there is something else I should check/consider. Seems very suspect that this behavior would simply coincide with all of these other circumstances.
THANKS in advance for any ideas (or words of assurance haha), and for your patience of course!

First thing anyone on here would say is to verify the pressure with a mechanical gauge. The senders are prone to failure, so check first before you begin to worry too much. Does it make any odd noises when the gauge drops to 0, like any knocking or tapping? If not, then it might just be a faulty sender. A good auto parts store should be able to rent you a gauge to check it with.

That, I will do (after figuring out how). No weird noises, no strange activity outside of the light and the gauge plummet.
I just didn't know how likely it could be that I was slowly killing the poor thing by driving it in that condition (has NOT happened on morning commute, although outside temp was only 75ish at that time). Thanks!

What is the pressure at driving speed, say 30 to 50?

Gauge sending unit unscrews and mechanical gauge screws on in its place. You really should do that soonest.

You can't tell anything about the system by feeling the radiator hose. I assume you are showing no overheating. If you have any reason to doubt accuracy of the temp gauge, get an IR gun and check under hood temps, particularly at the thermostat housing.

Normal oil seepage which a vast number of XJs have would not affect oil pressure.

Pressure reads around 40 and just above at start and until it warms up a bit, then it usually sits between 10 and 20. E-way driving is closer to 20-30, but most of my commute is miserable stop and go, under 40 mph for about 25-35 mins (unless I'm running late heehee). And yes - I will be scouring the cooling system write-ups over the next few days. Temp gauge goes to 210 and stays, never above or below regardless of conditions, just seems suspect to me. I haven't caught the 2nd fan in front (sorry - learning curve) turn on yet while it's running (watching with hood up). I can't tell if it pops on while driving b/c I simply don't know what it sounds like if I could presumably hear it.

210* is absolutely perfect. My '93 locks in at 210* after about 4 minutes driving (after a cold start) and never moves regardless of driving activity or ambient temp.

E-fan does not kick on until temp gets to ~218 or A/C is on. The e-fan on your '97 is a bit quieter than the one in the '93 and I can't hear mine when driving. My fan often kicks on for a few minutes when idling after a highway run and I can hear it then.

Your oil pressure readings are low and I would check with the mechanical gauge. Sending units and gauges tend to be notoriously inaccurate but you are not going to relax until you check it out.

Should be checked with mechanical gauge. If sender is faulty and you replace it, dealer or NAPA are two of the best places to get one. Short of hearing ticks and noises when pressure drops to zero, you can pull the oil filler cap and look down at the rocker. There should be oil pooling in there. When you shut the motor off, it will drain out. If you don't have oil in the rocker arm with the engine running, you definitely have a problem.

Mine is a 99, but I understand what you're telling me :) I will def find a gauge tomorrow and check that out (just struck out at 2 of the close-by auto places, but there are several small garages near my office). I'm guessing that actually buying an IR thermometer is a good investment.
Thanks again!

Duly noted. I hadn't tried looking in fill cap while it was running simply because I thought that would make a big mess. [blushes] I'll check it out though when daylight returns. Thanks!

First thing I would do is ADD ANOTHER QUART. I6 takes 6 quarts of oil, not 5

On mine nothing splashes out. If there is a ton of blow by then you might get some spray.

No. He left the filter on.

Which I wouldn't have done, since he changed to Rotella. What's another $5?

He should check it, though.

If oil pressure gauge turns out correct, he has likely got wiped bearings. Someone said sending units and gauges are notorious for failing.

Not as often as you might think. I would believe the gauge first, and assume that there really is 0 oil pressure until proven otherwise.

Another clueless soul who thought rotella would fix his toasted engine. There's the real oil myth.

Do NOT trust whatever ****ty filter the PO spun on. Filters affect pressure and in some ways are more important than oil so replace it!

Indeed your Jeep sounds perfecty normal except possibly a collapsed filter, busted oil pressure sending unit, or shoddy wiring to the OPSU.

Where on earth do you come up with this ****? The OP wrote nothing of the sort. He could have switched to Valvoline Premium for all it matters. Go troll someone else's thread.

What type oil was previous owner using? Can you ask him? I would suggest rotella 15-40. That is just a suggestion so take it as that.
If there is no noise and oil can be seen flowing on rockers at idle I would not be overly concerned. Your pressure comes up with rpm so your probably ok. VERIFY with a test gage and a look-see into the rockers.
The 4.0 with its wide bearings does not require a lot of oil pressure to keep it alive. FSM says 13psi but that is for normal conditions....things are not always normal.