goneboating06

Ok, so i have a 1989 jeep cherokee, with the 4.0L and around 186K miles. I just replaced the oil pump about a month ago and i am still only getting around 9-10 psi at idle, and around 2,000 RPM i get around 20 psi when its hot. when its Cold i get around 40-50 psi. My question is, could the reason for the low oil pressure is my main bearings being warn out? My jeep runs very well, it has plenty of power, it doensn't smoke, and i get around 20mpg city which is amazing.... so whats going on? Also when i shut my jeep off, a bunch of ticking noise comes from the lifters almost as if they are settling or somehting. Any ideas as to what is going on? Thanks oh, and also is it still ok to drive, its my daily driver, and if i do have to replace my main bearings its it a in depth process.....

foxrider4lyfe

everything you just typed i have the exact same problem...even the lifter tap afterward
i figured it was my oil pump failing but you said you just replaced yours?
im starting to wonder if its the sending unit of something being blocked

goneboating06

really? thats weird.... yeah i replaced my oil pump, and i have a mechanical gauge, so thats why i am so annoyed by it! i mean it runs good, but that seems like its pretty low oil pressure to me....

troy fritz

My 4.0 runs at 40psi at idol and 60 or so when driving.

goneboating06

really? so what is wrong with mine? is it just because its old? its been overheated once or twice.

sandstone

mine too

captainwoot

Mine is about the same 10-15 hot idle, 40-60 cold. I think it is worn brgs , typical lifter noises when hot. I think the shop manual will say anything over 5-7psi at idle is ok (at least as far as chrysler is concerned)
I'm at 230,00k nothing has changed yet. my last one was the same......

98 JeepJeep

Oil pressure is directly related to bearing clearance....the looser the tolerance the less pressure...........you prob have worn bearings.......

goneboating06

so am i ok to keep on driving it, or should i replace the bearings?

wanagojeep

u can drive around just fine just no real long trips or too much off roading. but i would replace them within the next 5000 miles or next oil change. takes a weekend to do.

foxrider4lyfe

i was out wheeling mine today and my pressure dropped to 0 and it started running funny then ran fine,strange but how hard would it be to change bearings??

wanagojeep

take the weekend, might need two people, not too bad. if you know what your doing, just taking the front apart. or are u doing both?

goneboating06

thanks for all the help... but i also have another question. So i am going to replace the main bearings, but do i need to replace the rod bearings as well?

daveman119

My 97 4.0 did almost the same thing. It would start around 5 psi then it would move to 40 when driving. It would also loose psi when accelerating. I pulled the ground wire off the sending unit and cleaned it real good with some electrical cleaner and put it back on. That was about two weeks ago and it sits at 40 at idle and around 60 when driving. My sending unit was right by my distributer. I have no idea if it will help but good luck

goneboating06

thanks i tried that, and my gauge is just messed up, so i put a mechanical gauge on. So do i have to pull the crankshaft out in order to replace the main bearings, or can i tap them out after pulling the bearing caps off?