Where's The Low Oil Pressure In A Jeep 4.0 Going? I Find Out! 

Your not a hackjob at all. I would describe you as a common sense get 'er done 'er. The world needs more folks like you who aren't afraid to try new things and learn from experience.

Dex you remind me of a guy that taught me a lot about general mechanics… he was a farmer and learned by fixing stuff that broke by watching his Dad/Uncles fix stuff… you are a great reminder of how resourceful he was and I like to be. Keep it up.

Dex, I am convinced that you have solved the low oil pressure at idle issue. There are going to be a lot of engines out there getting new cam bearings, thanks to you. Great work and be safe.

Best jeep channel on youtube hands down

I really appreciate you taking the time doing this To me thats one of the reasons i really like your channel Really enjoy what ya doing

I wish you were my neighbor, you stay in a good mood even when things are going bad, I usually get ticked & discouraged

This is what a mechanic 👨‍🔧 should be a problem solver fixing what needs to be fixed you are what I consider a real mechanic 👨‍🔧

Dex, I’ve recently found your channel and I’ve got to say it’s my favorite RU-vid channel of all time, plus, I’ve learned so much

Appreciate the effort to get to the root of the problem 🤔that's how we learn 👍👍

Its like we are in the shop figuring it out together. Wonderful job Sir.

I wish I could bring my 4.0 down to you so you’d rebuild it you do awesome work on these motors dex

I'm glad somehow i bumped into your channel. Nothing but interesting good stuff.

Well well well - apparently Ol Dex has been hidein sompin - he has been “camshaft illiterate” the whole time - he said it had a bad johnsonator. No matter I just learned a lot about the 4.0 camshaft -

DEX posted a short about traction. Full send VS Flat. Video Auto played before bed. Next morning Chicago got hit with so much snow. Then I remembered what DEX said. Just kept it full send. Didn't get stuck once.

I’ve got a 1999 XJ with 307,000 miles on it. The oil pressure has been slowly dropping over the last 50,000 miles or so. I replaced the rear main seal at 250,000 miles and the rear main bearing looked brand new, so I had been presuming that the dropping oil pressure isn’t related to worn rod or main bearings. I was thinking it might be a worn oil pump, but after seeing this video it’s got me thinking worn cam bearings now. I’ve still got 20 psi at hot idle and 50 psi when revved up so the oil pressure is good enough, but when it drops enough to start worrying about it and I yank the engine it’s definitely getting new cam bearings. Thanks for the hard work to figure this issue out.

Dex out here taking one for the team, thanks brother xj all day!!!!

Thank you for all the work once again. That new camera works great!

That’s pretty nice. Lots of information and tips. Once it warms up I’m gonna use some of the knowledge I’ve learned from you on my yj.

Excellent! There's 1000s of this engines out there with the low oil pressure problem and finally I know what to do . thank you for making the video .

I’m really enjoying these videos, thanks for taking the time to get these out there. My xj has identical oil pressure symptoms, gives me something to look for now.

Dex out here teachin me more than school ever did! Thanks brother

Yay!!!!! That was me who suggested the oil dye. I have a different account now, but it was pigtrapper2 when i wrote it.

I just want to say thank you. I have personally run into a few motors similar to this one. Some had the dreaded cracked head issue. Even after a new head, and new rod Bearings they still had low oil pressure just like this one. To me, you have just proven that cam Bearings really are the only way to fix this problem. I tried high pressure pumps as well, and it didn't make any difference. I had chatted with a few people that pointed to the cam Bearings being the problem, but you just proved it without a doubt. THANK YOU SO MUCH.

Uncle Tony’s garage brought me hear and I’ve enjoyed it

Decks by Reading all these messages you've already helped tons of people out with the same issue.. This proves the time and effort you put in do this video. Was worth it keep up the good work .

Ignore the haters Dex and do what you do your doing good..

What a great video! This is without a doubt why my forgotten Cherokee had persistent low oil pressure issues. I chased that issue all the way up to the point you were at when you started this video. Thank you for solving this mystery!

Glad to see the old, drill on oil pump trick helped you see that cam issue. Would have been tough to come to terms with the issue just by checking the timing chain. Nice job Dex 🤙

It's very interesting. Hope you figured it out.

I like how your going though the trouble of this to figure it out. I don’t think your a hack job. Keep up the good work

Dex, you are awesome ! ! ! Thank you for completing this series. I really enjoyed it. Shoot, I enjoy all your mechanic videos. Keep it up 👍

Man yeah that's awesome!

You worry too much about comments. Take the good, ignore the rest. Even me if you want to.😉👍

Thanks for doing the work to prove this out!

Good video, nobody lied to ya

Well done ...🤙

Always awesome videos

It’s not hack job for the common man that doesn’t wanna spend 10 of thousands of dollars fixing his stuff your not a rich RU-vidr I can’t relate too your a relatable guy too just a guy trying too fix stuff in his shop and not spend a fortune appreciate your videos!

Good job working it out 👍👍

I love what you're doing. I wish that you'd been making videos years ago when I bought my first XJ. Could've taught me all that I needed to know before I had to learn it the hard way. Also, yes, cam bearings are the #1 cause of low oil pressure at idle.

Nice! I like that you didn’t give up

Love your videos dex im learning alot about jeeps from you thanks

I started having oil pressue issues at about 260k. I also discovered my 0331 head was cracked at about 260k. The head was replaced with a rebuilt head at 280k and I tried changing the oil pump at 300k with not much improvement. I have been running 15w40 rotella for 55k miles with 20psi hot oil pressue. Previous to that my oil pressure would fall below 10psi and the light would come on. I know this is not a long term fix but if you want to eek out a bit more life from an engine needing cam bearings, before rebuilding, this has been working for me.

Another great video from dex

great info

Another great video!

Great video Dex!

Nice detective work Dex!

Thanx dex great video

Good job 👍

Thank you so much for going to all that effort. I learned a lot. Your videos are great.

I dig your XJ content! Subbed

I saw the title of the video and went "yeah probably cam bearings" and I wasn't disappointed lol. Nice find.

Hope it many moons before my stroker has low oil pressure issues but this will definitely be checked first if I do! Thank you for everything you do best account on RU-vid

Brilliant. I've been working on AMC engines all of my life. The school of thought was generally "all bearings slightly worn" so throw in a high volume Melling if the hot low oil pressure issue arises. But I always suspected that it was a more specific area as the pressure swings while driving were so dramatic. If all the bearings are worn out, you'd end up with a lower overall loss in PSI, not up and down 20+ PSI with the throttle at any given temperature. Great work and I'll be pulling my cam bearings during the refresh this summer.

This is one of the most informative videos I’ve seen in a while. On any Chanel. It never occurred to me that you can have an oil leak inside the motor. This might be what’s wrong with my 4.2. It drops to 5-10 PSI when hot and idling. 160k miles on 89 YJ. Keep the videos coming.

Wow thanks man

Good video thanks for giving me something to watch and learn from.

Your brother biting his tongue was cracking me up, he loves you very much. I have to say it's really awesome to see you experiment and see what happens sometimes. At least when you do something that's not by the book you're honest about it. Now your camera work on the other hand leaves a lot to be desired 😂

Beautiful

I would love to see your brothers process, he has his way and thats ok, it may teach others a way that is better. 😊😊😊😊😊

good job........ dont mention the haters, act as if they dont exist, praise the good commenters, grow your channel

Good video!

Thank you for solving this issue.. alot of cam bearings will be sold tomorow...also ill be looking for this problem on the next 4.0 i get ahold of

Just my own story and hope it helps the next guy. In my case minimal oil pressure after a new 4.0L rebuild. Turned out to be the newly purchased China oil pump relief valve cracked open & stuck. No reason to replace the 260K mile OEM pump during my build as it worked fine just seemed new during a rebuild was the way to go. Had to do another rebuild as defective pump with open releif valve finally burned my lifters, cam lobes, crank bearings, and push rod bearings from lack of pressure, all because I did not believe my oil pressure gauge. Runs like a Champ now...lesson learned. If your going with a new China pump double check the relief valve is closed, not stuck open, and opens and closes properly. I'll reuse the China pump someday after honing out and polishing the relief valve bore. (Why even have a relief valve on a 4.0L oil pump?...sure there is an answer somewhere but I don't know.) Big fan of common sense and down to earth mechanics. Also, I too pull heads with the intake and exhaust still attached...makes life easy during the re-install. I use dowl pins to guide the head back on as to not damage the new head gasket. I for one got burned on low cost head gaskets from local auto supply store, I only use MLS head gaskets now as added insurance.

I have been wondering why the 4.0 has lifter noise and worn rockers and start making noise. The same ro kerarm and lifter design was in common use and problems were rare. You have actually revealed the root cause of several complaints that are common on this engine. My hat is off to you sir!

Awesome!

I just found your videos I think there cool, I’m a jeep Cherokee and 4.0l lover my self !

The footage with the new camera is real nice, it's a big difference

The right side of the motor is where the lifters and pushrods are, so it will read cooler on that side. Good job finding the bearing problem.

Next I mentioned this to you on a previous video in the comments I know about this. It happened to me and the Achilles Hill with these 4 row motors is the cam bearings. I've seen it on several videos on RU-vid. Also, put heavy oil in it when you first started up. Let it break in after that change it to regular stuff. I use 10/40 when I fired up my engine. The first time I wanted to get the Heavy oil film to start and break in my cam. And everything else after that I change back over.

My dear friend Dexter, I feel like you are preaching straight to me brother man. Just did an engine swap to get our family xj going. Bout to make a 3 row xj. :) Went well, however I noticed that the motor I swapped in (244,000 miles 😅) has the issue you described of having low oil pressure once up to temp. I am about to replace the entire cooling system and the tires on it with income taxes, because i belive somewhere therin lies my hot running temp issue, which exasserbates the oil pressure. Oof wish me luck, as I buy another used cherokee to pull another motor and do a full engine rebuild on this engine otherwise. Money pits, gotta love em.

I can relate. I bought a CJ7 with a rebuilt Jasper engine. Engine is 5 years old, but less than 10 k on it. It goes from 50psi down to 10 at operating temperature at idle. Off idle it goes up. No funny noise.

Nice work! I’m the type that has to stir over what caused the cam bearings to wear out. I’ve been bitten by cam bearing issues once. The problem became obvious after a few months of head scratching over it.

Great job. I have the same issues with a 01GC when hot at Idle the check gauges light comes on and there is 0 on the gauge I sit at a red light with it reved up some to keep oil pressure and my engine piston slaps bad also lol it needs a full rebuild, maybe someday

Guess i need to pull the motor out of mine and have justin put cam bearings in it lol. Mains and rods looked great when I put it in but it has always had low oil pressure.

Looks good Dex! Wish I knew what happened to the Comanche, even if you had to give up and move on. I just finished a 5.3L rebuild that went well.

Main bearings and cam bearings are almost always the culprit in low oil pressure issues.

My dad and I put cam bearings into his 5.3 when I was like 17. Because of low oil pressure obviously after looking at all of the rod and main bearings which by the way looked perfect for 300,000+ miles. So one of the cam bearings actually spun out of the block. We replaced all of the bearings but the original cam went in hard and I’m not sure if the cam was warped or if the bearing tolerances where to tight. I saw a hagerty video not long ago showing to put cuts in the old cam to act as a drill bit if you know what I mean. Clean frequently and flush the oil passages and you’ll get a perfect running engine if you have cam bearing clearance issues. I forgot to mention the engine had good oil pressure for a little bit but lost it again because I think it spun another cam bearing

I want that motor!

F*ck the haters!! I enjoy watching your videos!!

1989 4.0 with 179k miles has 35-40psi HOT oil pressure. Jumps to ~50 at a cold start and stays around 40 while driving. I'm so glad not to have this issue *knock on wood*, but it makes me wonder what really causes low oil pressure in a 4.0. It seems not to be related to mileage... has to be lack of a proper maintenance routine, right?

I did cam bearings and mains and rods. Still didn't have oil pressure. Only thing I didn't change was the cam itself.

spec. oil clearance on a cam bearing is .001-.003. looks like someone mixed the up cam bearings on the original install for them to come out so easy. the insides of the bearings are the same the outside is different sizes for each journal, they have to go in order 1 through 4 . I'm not telling you I'm telling those who are watching who don't know and because you said the journals on the camshaft are different, they are not its the block that's different

Dex, I was thinking about the black Comanche I’m thinking the oil passages you show in this video are semi obstructed in the Comanche’s engine. The oil flow is restricted in them so it has no where to go but lifters. They pump up and the issue exposes itself. That’s why it holds oil pressure like it does after it shuts down. That oil takes a second to bleed off.

I noticed you used oil dry. Aka diatomaceous earth for the oil spill. Highly recommend red clay. Aka Georgia clay. It’s way more absorbent than oil dry. And it’s free for us southern folk.

The book says it will be only 13psi at 600rpm and 36psi at 1800rpm. Iv changed my oil pump twice. Cause i cant stand it being at 20 sitting at the light. Found a way to increase pressure up to 65 at start up and 25 at the light

So I’d definitely love to see a Dry Sump system down the road. Any hack way. Lol. I plan to run a Volvo electric power steering setup, and a BMW electric water pump. Putting a 4.2 crank and rods in a 4.0 and I want to experiment with freeing a 4.0 up as much as possible. Maybe smack a valve or something eventually who knows. 🤘🏼😁🇺🇸

Awesome job keep it up fk the hater’s

Well that seals the deal for me. My idle oil pressure will be 10 forever.

Based on the result from this video i would check and see if the cam bearings or cam its self in a renix are different measurements than a newer cam or maybe they beat the bearings in the wrong order and forced the cam in i think the cam is to tight some how and holding oil pressure

Cool video. Did you happen to check if the crank or cam are warped, causing the uneven wear?

That guy who called you a hack job is going to see you and your brother both rich from this channel! Watch

What’s the bottom $ for that engine?

Brother, you need to replace that cam. It's wiped out on the journals. It will ruin new bearings. Great video.

I love innovation Dex, its just a precision form of hack. But, I also worked for HANK the CRANK INC.at one point, and so I know that you shouldn't be removing those bearing journals material, if it moved sideways before, now it will move even more, you will need a lot thicker oil to fill the extra space.made unless you get undersized new bearings and make them match the old out of spec cam. NOW THATS A HACK. Hack is a word used to say stupid. Not smart, but innovation means you can be stupid in your attempts to discover whats right. Personally I think you should just put new bearings, cam, new lifters and show your worth, because I know your not stupid, reserve hacks for emergencies and on the trail repairs, but never bring them to your shop bro. Just do it right and it will work. 🤔👍

I wonder if this testing will help with finding answers on the commache as its clearly some sorta oil pressure issue

Any way to pull out that back Cam bearing from the front so I don't have to pull my motor

I’ve been dealing with this problem for two years.

Like and share everyone 🎉