cgrossl

I guess a small introduction would be appropriate for my first post here. I am a car/truck guy. I've been working on them, restoring, hot rodding, etc. since I was 16. I've lost count of the engines that I've built. Basically, I would would like to think that I'm not an idiot when it comes to this sort of stuff, but I definitely don't know everything and I'm a new Jeep owner....so I'm here to learn.

Earlier today, I bought a 2000 Jeep Cherokee Classic with 102,000 miles on it and the 4.0 I6 engine. I wanted a Jeep because of the legendary drivetrain, and I had a roommate that had a 97 Limited several years ago, and I loved it. So far, I'm tickled to death with mine, but I am concerned about the oil pressure.

Anyway, I did a search, and read for quite some time about several others on this forum who also have, or have had issues with low oil pressure with the 4.0 engines but, I never saw much of a solution to the problem, other than the lucky ones who just had a sending unit problem.

Right now, I am getting abouit 8-10 psi at idle and 25psi or so driving down the road when the engine is warm. I have already replaced the oil pressure sending unit, but there was very little change. I am going to install a mechanical oil pressure gauge tomorrow just to check it against the factory gauge, but I kind of expect it to read about the same. My next step will be an oil change, but again, I really don't expect that to cure the problem. But hey.....I could get lucky.

Next, comes oil pump replacement, and here's where my questions start. Those of you who have replaced the oil pump, or had it replaced....did it solve the oil pressure problem? Did any of you disassemble the oil pump to see if the oil pressure relief mechanism failed in any way? It looks like I will be able to put my Jeep up on jack stands under the "frame" rails, letting the front axle hang, then jack the engine up, remove the starter, maybe the exhaust, and then remove the oil pan, and the pump. Does this sound right? Am I missing something?

If it does come to oil pump replacement, I'll probably pull a couple rod and main caps just to take a peek, but based on the way the motor sounds, I'm expecting to find good bearings. Plus, I find it hard to believe that the bearings are that worn at 102K miles. Hopefully, I won't be building my first 4.0.

Thanks,
Cameron

RoyalXJ

for every 1000 rpms you should have 10 lbs of pressure to be safe. if your worried replace it with a new stock pump

TheGreatGazoo

I Just changed my oil pump today. i had the same oil pressure as you and it scared me. so i replaced it with this one( click the link below) it took me about 4 hours from start to finish. i had to remove the starter and remove any ties holding the transmission lines to pull them over to the side. i jacked up the front and let the axle hang down and had pleanty of room to get the oil pan out. Now at idle in gear i have 40psi, in nutral i have 50 psi, and highway almost 65psi. this pump is worth the little extra over a stock pump i highly recomend it.
http://www.summitracing.com/parts/DCC-4529241/
here is the oil pan gasket i got too

http://www.summitracing.com/parts/FEL-OS34308R/

cgrossl

Cool, that's exactly what I wanted to know. Did you disassemble your old pump to see what was going on?

You didn't have to jack the engine up?

TheGreatGazoo

no i didn't take it apart i still have it in the trash can maybe i will pull it apart this weekend and see .
and no i did not have to jack up the engine BUT i have a 4.5" lift so that may give me a little extra clearance. if i was you i would disconnect the front shocks and jack it up from the body and let the axle drop that should give you pleanty of room to get the pan out.

cgrossl

Good idea.

AFMan

Did you have to pound out some more space in your oil pan to make it fit? I heard with the high volume pump you have to do that. Let me know.

TheGreatGazoo

Nope accually after putting the pickup tube in it was about 1/4 inch shorter than the stock one so it has just enough clearance with out hitting the pan. it was a direct bolt in no mods needed.

AFMan

Hey Cameron,
I am totally going through the same symptoms, and I replaced the sending unit, and mechanically tested the oil pump, and it appeared to be fine. But the problem still exists. So, I think I'm going to replace the oil pump next. The pressure readings you described are practically identical to mine, except when I idle at a light long enough and the engine is warm, it drops from 10 to zero and a "check guages" light comes on.

Regarding replacing the oil pump. Per my jeep repair manual it says you only have to remove the oil pan, so I was confused when you stated removing the exhaust, and the starter. Is that really necessary? Good luck to both of us.

AFMan

I just bought a stock pump. It came with the pump and gasket, but no pickup. Can I use the existing oil pickup, or do I need a new one?

RoyalXJ

you can use the existing pickup just make sure you take some brake cleaner or something and clean it out

Rmart30

If you have true low oil pressure on a 00 or 01 model is usually a cause of the 0331 head cracking and seeping coolant into the oil and wiping out the bearings.
The 0331 cracks just under the oil fill cap and coolant slowly mixes with the oil. Usually you can take off the fill cap and see a greenish tint.

Google 0331 head and a ton of threads will pop up on it..

cgrossl

I did read about the 0331 head cracking issue. I don't believe that mine is cracked. The oil doesn't have any water in it, and I didn't see anything unusual under the oil cap.

But, like I said, if I end up replacing the oil pump this weekend (and that's what I'm thinking that I will be doing), I will pull a few rod and main caps to see if there is any abnormal wear. According to the previous owner, the oil pressure thing just started a short time ago which leads me to believe that bearing wear really isn't an issue. But, I have been wrong before, so we'll see. I'll report back with what I find.

AFMan,
From what I saw under my Jeep, it looked like I might have to remove the starter and/or the exhaust to get to some of the oil pan bolts and just to give me more room to move the pan around to get it off of the engine. I don't mind removing the starter, but I really don't want to have to remove the exhaust.

Mike H.

I did not have to remove the exhaust.
I did have to remove the starter.
If the Jeep has a short lift or is stock, disconnect the sway bar and shocks to allow the axle droop out of the way.
I went with a stock replacement pump from NAPA... $20 and reused my old pickup and screen.
I have 45psi at idle (5spd) and 65psi by 1800rpm.
Motor has 183k miles (295k kilo's)

98 JeepJeep

I have a Melling OE Style Pump waiting to go in mine.

IMO no need for a high volume pump on a jeep.

My advice to you REPLACE THE REAR MAIN SEAL!!!! just a few extra $$ and your there.

Most people seem to forget that the oil pump is the first and only thing that gets dirty unfiltered oil.

So when pressure is low they blame bearings.........