Ok so i'll start by saying i have a 97 xj 4.0 ax15 np231 lifted 4.5" on 33's I've been having an oil pressure issue for a while with my jeep it happaned after i went on a good hour or so drive in it a year or so ago. I don't drive this jeep every day but when i do it's usually about 45minutes to were i'm going and then 45 minutes back. After i get off the highway i always get stuck at the same light for some reason and my oil pressure will drop down to 0 and the check gauges light will come on the first time it scared the heck out of me and when i started driving it slowly went up for every 1,000 rpm the oil pressure goes up 10 so cruising at like 2500 i have like 25 psi. when the jeep is cold it stays between 45-50 no matter the rpm I replaced the sending unit and checked the elbow that it bolts to for sludge it was clean as a whistle for having 210,000 on it. I have thought oil pump but at the same time i think that having 50 psi at cold and having 0 at warm/hot idle is leaning towards something like main bearings I was hopeing to hear some good opinions before i find a used motor to drop in there.

 

You're right, bearings.

You can try straight 40W and a quart of Lucas. That will help keep your pressure up until you can rebuild or replace.

 

I have been running 20-50 and one of the thing's that supposed to help I don't remember what it's called though. I didn't want to waste money on an oil pump on a **** motor. If i get a used motor i'll be putting a new oil pump in along with as many gaskets/seals as i can replace with out having to take the head off. what do you guys recomend for oil pump? I found a mopar high volume one on summitt for around 100.

 

I have the exact same pressure readings. It might make you feel better if I tell you it has been that way for over 40k miles! I bought another engine for when and if it ever blows. Four years ago I found alot of metal flakes in the oil when I drained it so I suspect a cam bearing walked out of its bore. Engine runs great and is quiet. Very busy daily driver, it will run 70mph on interstate all day long. So have no fear and drive till you hear noises! At 210k your engine is probably tired but it could go on for much longer.

 

Yeah, I'll second your take on it.

We had a 98 with the same symptoms and just kept driving it until the wife totaled it.



OP, spend your money and time on building a new engine......I would not waste $160 ...pump, oil, gaskets..etc

Not to mention the time.

 

I guess i forgot to put in the original post. It always tick's a little bit i'm guessing lifters but after it get's warm/hot it ticks louder and has a very slight knock.

 

Yeah, mine too but that subtle knock when warm is fairly common in 4.0s regardless of oil pressure.

 

Could have a bolt loose on the flex plate..

https://www.cherokeeforum.com/f51/ho...ocking-125547/

 

Already checked that. Bolts are tight. Noise is not exactly like video. I have heard many 4.0s ( especially 99-01) make the same sound as mine. These are the same years with the mysterious low oil pressure issues too. Does not seem to hurt anything as I have seen them reach over 200k with that noise.

 

What brand of oil filter are you using?

 

As cruiser said. What brand of filter? A crappy filter can and will make a difference. Also, 20/50 oil is too thick and you also don't want to add any of those oil additives, thay are just a waiste of money. A goog quality filter and good oil should be all that you need onless you have bigger internal problems.

 

Amen. some people have trouble understand oil pressure. If you use thick oil and additives to increase pressure you have just defeated the function of lubrication because you DECREASED oil FLOW. Flow is what lubricates....not pressure. Low pressure indicates less restriction (worn engine) and increasing pressure does not correct that problem!

 

No flexplate on a manual tranny. And i can't get to the flywheel bolts with out taking the tranny, pressure plate and clutch out.

 

I get free mopar filters from my uncle. If i run 10 30 it's real noisy and burns oil faster. I put 20 50 in and it quiet's it down bring's pressure up a bit and doesn't burn as fast so... I'm guessing there's nothing wrong with mopar filters i've never had an issue with them. or heard anything bad about them.