BRANDONXJ

Ok so my 1998 4.0 xj is having low oil pressure problems and when its been running awhile at low idle it will drop to none. It runs really low all the time more than the other 6 i have owned. Im a jeep freak lol. Do i just need to replace the oil pump and is this common? If so should i go with the high proformace pump with 20% more flow?

darknezz

Mine runs 20-25 while driving after warmed up and drops down to 10-15 while at a long stop. When I first got it it was more like 10 while driving and near 0 when stopped, I changed the oil with 10-40 and it went up to what I said above.

My first vote is to change the oil with 10-40

BRANDONXJ

Just had a new oil change that i tried and used 20-50 for that reason little to no help.

hubs97xj

Rent/borrow/buy a mechanical tester, and see if you have low pressure, or just a bad sender first.

BRANDONXJ

Totally understand what your sayin but when the pressure drops to 0 and i rev it it will blow a little blue smoke and pressure comes up for a whlie (a few min or will stay up if i keep it above idle) then it drops again. Wouldnt that refer more to a oil pump not working and not just a gadge?

AFMan

I would:

1) Change the sending unit
2) Do a mechanical check
3) Then change the oil pump
4) Use 40 weight oil

I've had done all but change the oil pump because I'm not sure it's actually broken, and don't want to go to the trouble unless I'm sure. I put in 40 HD oil and it holds at a higher level now, but drops to 10psi still when the engine is warm, and I'm stopped at a light or at idle, then drops to zero and causes the "check guages," light. It seems(oil pressure indicator) to maintain higher at under 200 temp. Otherwise, when it is warm, it will maintain about 25-35 when I'm on the the highway, which leads me to believe it might be the guage, rather than the pump.

Good luck on yours though.

Purp

Using a mechanical gauge to see if it's your factory guage, is a heck of a lot cheaper than spending the 80 on a new pump.

But the sending unit is a very common thing to go bad. It could possibly be that.

I have the same issue with my 99. I changed the sending unit and that didn't fix it. So, then I replaced 2 oil pumps. I still have the same problem. My lifters started ticking bad and I get a rattle at about 3K rpms. I'm just going to drive it till it blows. lol

BRANDONXJ

if you did all those things what would cause it to still have low oil pressure? rings?
ine has 130k seems low for a jeep to have this prob.

Rmart30

Rings have no effect on oil pressure.......most of the time it is worn bearings and installing a new pump increases volume/pressure sometimes enough to keep them going for a while.

130k is low for this problem but the question is how well did the previous owner change the oil and did they run the $1.99 quicky mart oil in it ?

BRANDONXJ

ahh that makes more sense. so i guess try the pump first and if not rebuild huh. thx for the help

Throttle Jockey

go ahead with the oil pump and while you got the pan off, i would roll a set of bearings in it and let it eat.

BRANDONXJ

how hard are the bearings to do and is that all i would have to do?

Throttle Jockey

the bearings are a breeze, rods are a piece of cake provided they are standard size. you should probably plastigage them to make sure you dont need to go oversized. mains are a bit harder but not too much. same thing on those. plastigage them to verify size. a new pump and bearing should bring your oil pressure right back to original and you wont even have to pull the head off unless you want to do the top end also.

AFMan

Which bearings exactly??

Throttle Jockey

rods and mains