The rear main seal saga

My jeep has 146,000 miles. 01, 4.0L, aw4.

It leaks oil.

I've thought it was the rear main seal, and not the pan, or oil filter adapter. Im running Mobil 1 10w30

I pressure washed today, and sure enough, it seems to be leaking from the rear main seal only, and enough to cover the tranny in oil.

Here's the question.
Who do I believe? I took it to two shops today. One was a jeep specialist. One was not. I want to do the work my self, but I need to know what they wanted to do.

The jeep specialist said- It's the main seal, and because I'm using Mobil 1, it's leaking out. He says Mobil 1 is such good oil, that it leaks out through the big tolerances our motors have. He says, switch to a castrol 20w30, and it may slow the leak a bit. He says it works better for the older technology. He quoted me 486 to do the whole replacement. He also freaked me out saying, if it's leaking, you might have a scored crank bearing. He says the rear mail seal is rare to go out.

The non-jeep shop said- It's leaking, but the mobil isn't the problem. The positive crank pressure pushes on the seal, stopping any type of oil you use. They quoted me $860 to do the whole job. They said that they have to pull the tranny. I lol'd and said, "no, it's a two piece seal, and you can pull the last bearing cap." The guy said, "Don't just pull one bearing cap. You'll stress the other caps, and you will have to re set the tolerances, using plasti-gauge, and you'll be pulling the bottom of the motor apart." Is this true? I see so many of us doing this in the driveway, but they want to pull out the tranny, and re build the crank!

Let me know what you think. I will be doing the work myself, but I just need to know if pulling the last cap is the "ok" method. And is mobil 1 to blame? Thanks!

-Sean

just do the seal urself.....do the o rings in the filter adapter and wear a shirt u dont care about. no need to "reset" tolerances....even though theres no reset button on ur crank bearings. just pull the first one and crack the second one somewhat free and lube the hell out of the sealand SLOWLY slide it in the slot. u prob know the rest. i used a small light spring with half of it straightened out to slide in the slot and grab the seal then i pulled it through slowly...just buy 2 so u can beat the learning curve. :greensmok

I think both of those "specialists" are full of crap. Verify it's the rear main seal and do it yourself. Nuff said!

when i replaced mine i didnt have to drop the tranny. i just unbolted the end cap knocked the old one out and slid the new one in. was really easy. that hardest part was gettin the oil pan out. with 3 in of lift i was still hittin the front axle. my crank or bearing wherent scared the slightest. i dont see it bein the oil. they are known to fail on our jeeps. i have known of a shitton of them that where leakin or had been replaced

cruiser54 said:

I think both of those "specialists" are full of crap. Verify it's the rear main seal and do it yourself. Nuff said!

Click to expand...

They are "special" specialists, as they probably rode the "special" little bus.

Other than an Obama speech I haven't heard so much crap in such a short time in my life.

Jeep 4.0 RMS will leak, not a question of if, but a question of when.

Using synthetic motor oils MIGHT have cleaned out some crap that was holding back the oil, but it was going to leak eventually no matter what oil you used.

Your engine calls for 10w30, not 20wXX.

Did either of the "specialists" offer you dinner and flowers? They sure are trying to screw you.

Do the seal your self. While you are in there torque all of the rod and main caps to spec.

There are probably 20+ write ups on doing the RMS, probably 250 threads talking about it.

Xwhatever.

Specialists are full of crap, that's for sure.

What the second guy did get right is that you may have a crankcase pressurization problem blowing oil out through it. I have that right now in my MJ, most of my air filter is soaked with oil also... should probably get around to fixing that sometime. My CCV system is probably plugged, either that or I have a serious blowby issue. I'm hoping for the former.

Thanks for the replies.
I just wanted the opinion of the forum.

I'll do it myself.

But seriously... every goddamn thread these days has some mention of Obama. (And why in the tech area?)

Make it stop! I come here to escape the bullsh** of life, (including stupid politics) and talk about jeeps.

Thanks!

:roflmao:

Wow. Reset the tolerances? Big tolerances? And these people actually work on cars in a "professional" capacity?

Redneck engineering.

redneck engineering=built to hell blown ass v8. i really wonder why rednecks can make v8 so bad ass yet are apparently bad at body work

kastein, have you seen my previous posts about excessive amounts of oil in Renix air filters? If not, let me know and I will share an old Jeep engineering fix for it. It will only cost you a valve cover gasket and some time.

I think I have... cut off about an inch of the tubes that go into the valve cover? Not sure, but I think I remember that. It's on my list of Things To Do.

Half inch off each tube. Measure up half inch and drill a half inch hole in each tube on the rear facing side.

cruiser54 said:

Half inch off each tube. Measure up half inch and drill a half inch hole in each tube on the rear facing side.

Click to expand...

I dont follow... Maybe its just one of those days. Can you explain a little more?

Check the valve cover gasket too or just replace it because it will leak too. The rear of the valve cover is known to leak down the back side of the motor down the bell housing creating the look of a bad rear main or magnifying it so since you will be covered in oil any way do that to. And that's a crock about stressing the other caps its a 4.0 nothing stresses those things. As for mobile 1 it didn't create a leak it just helped it out a bit if you are happy with it run it.