Jeep 4.0 rear main seal thoughts

[Jms76]

Purchased an ATK 4.0 rebuilt engine for my 98 wrangler last fall. Within a month it developed a small drip that works it way down the transmission cover and drips. This continues today. It is not an oil pan, valve cover, oil filter related leak. It is similar to all RMS leaks experienced in the past.

I’ve tried both Pennzoil and Valvoline conventional and synthetic blend high mileage 10W-30 oils to possibly condition the seal with no avail.

The engine has a 3 year warranty, so since I installed it covers parts, but no labor.

I’ve read the many write ups and watched numerous videos on the process.

I’m not overly excited to change the seal, just because the upper seal seems to be easily damage despite being very careful.

Rather, I’m thinking of pulling the cap, cleaning the surfaces, replacing the lower RMS and seal with anaerobic sealant.

I’ve not seen many or any threads about taking this approach. The engine only has 4k miles on it.

Maybe it wasn’t fully seal on rebuild. Also, since it leaks and looking at oil levels and engine angle, seems like the lower seal may be the issue.

Would appreciate any thoughts and insight.

 

[pagrey]

I'd forget about it, keep trying different oils and see what happens. Mine has leaked well over 100k and I've never had to add between changes. Unless your parking spot is epoxy and pretty I wouldn't worry about it one bit. Think of it as rust protection. I have friends that replaced it multiple times to get it right only to have it start leaking a few years down the road.

 

[eastbloc]

Drips are good not, seal replace you must.

Maybe it wasn’t fully seal on rebuild. Also, since it leaks and looking at oil levels and engine angle, seems like the lower seal may be the issue.

I am failing to follow your logic and understand how you came to that conclusion.
The thing you have to keep in mind, two halfs are cut to mate each other as one. You put another half in there that is not matching the mating surface of the other, there is a good chance you will end up with a bigger leak than you began with.

 

[Jms76]

Yea, my dilemma. Never have to add oil, just annoying and hate seeing drips at all. My thought is that I’ve got a great shot at fixing it with this approach. Worst case feel it will be the same then I know the upper is the culprit.

 

[pagrey]

Worst case feel it will be the same

You might read about people who didn't succeed at this and see if their fails were all "similar" to their original leak.

 

[Jms76]

Drips are good not, seal replace you must.


I am failing to follow your logic and understand how you came to that conclusion.
The thing you have to keep in mind, two halfs are cut to mate each other as one. You put another half in there that is not matching the mating surface of the other, there is a good chance you will end up with a bigger leak than you began with.

My version had the tabs on the lower portion. Yes, they mate but I don’t see why the won’t be identical. The seals pretty much are all the same shape regardless of manufacturer.

 

[Jms76]

I’ve been unable to find any thread where this was attempted. Otherwise would of not created a new thread specifically on this.

 

[pagrey]

I’ve been unable to find any thread where this was attempted. Otherwise would of not created a new thread specifically on this.

Re-reading your original post, are you suggesting replacing the entire seal with anaerobic? You should probably read up on what that stuff really is. It only cures metal on metal with very tight clearances, I think Permatex says 0.015" so you can't really fill any gaps or make a seal. It only seals where the bearing caps are pressed together.

 

[TJ Jim]

There is a thread on here that one of the members did exactly what your thinking. He didn’t replace the lower seal, just added a dab more anaerobic sealer. He is claiming it to be a success. I’ll hunt for the thread and point you towards it.

 

[AndyG]

I'd forget about it, keep trying different oils and see what happens. Mine has leaked well over 100k and I've never had to add between changes. Unless your parking spot is epoxy and pretty I wouldn't worry about it one bit. Think of it as rust protection. I have friends that replaced it multiple times to get it right only to have it start leaking a few years down the road.

Amen. My thought is “they leak”. Non synthetic oil stops a leak for some owners.

 

[TJ Jim]

I’ve been unable to find any thread where this was attempted. Otherwise would of not created a new thread specifically on this.

Check out post number 53
https://wranglertjforum.com/threads...t-is-giving-me-fits.61077/page-3#post-1125578

 

[eastbloc]

My version had the tabs on the lower portion. Yes, they mate but I don’t see why the won’t be identical. The seals pretty much are all the same shape regardless of manufacturer.

Ahh you have the earlier design, i see what you mean now.
I don't know man... im just looking at it from my perspective, if i go through all the procedure of taking it apart, while oil and dirt falls on my face, sweating and feeding mosquitos in this heat, and after all of that it leaks just as much if not worse... that knowledge that i could have changed upper half while i was there

.... but you know you self better, more power to you

Try applying more anaerobic sealant, i don't think that factory manual calls for enough of it around the seal area.
I think Irun did his once and and his sealant partially did not cure and partially washed away by oil. After i took mine apart for the 4th or 5th time i could see lack of sealant around where seals meet.

Edit: TJ Jim ^ gave you link above to what i did, big thanks to him.

 

[Jms76]

One of my assumptions here is ATK didn’t put enough sealant on the split line joint. I’m skeptical of this for two reasons: a. It leaked near instantly. b.Had to fix three water leaks where they either did not apply sealant to the threads, or applied sealant too high on the thread where it didn’t actually seal the threads - like the #11 head bolt. So I’m almost thinking of pulling it apart, inspecting the lower seal and checking to see if they applied any sealant at all.

You’d think a rebuilt engine wouldn’t have a bad seal since the upper is installed prior to the crank. Unless installed backwards, which I doubt or it would probably leak a bunch more. The lower seal would be hard to damage.

I’m really think the seal is fine, just too little or no sealant applied on split line resulting in a small leak.

 

[Jms76]

Re-reading your original post, are you suggesting replacing the entire seal with anaerobic? You should probably read up on what that stuff really is. It only cures metal on metal with very tight clearances, I think Permatex says 0.015" so you can't really fill any gaps or make a seal. It only seals where the bearing caps are pressed together.

No, just leaving the upper seal in, replacing the lower only and then using anaerobic sealant to seal the split line.

 

[Daryl]

Remove the cap, clean the mating surfaces and place the sealer as the FSM states.

 

[Jms76]

This looks like you only apply a small amount to the block side, non on the lower cap as pictured above?

 

[eastbloc]

When you step into a pile of shit, does it matter whether it was on the ground or your shoe to begin with?

Regardless of where you apply, keep in mind that my bearing was seeping oil over mating surface every 2-3 minutes as if it was programmed to do that. So keep an eye on it, dont rely on surface staying oil free just because you cleaned it earlier.

 

[Claybirdd]

Switching to Castrol GTX high mileage which is a slightly thicker high mileage oil solved my small leak.

 

[Jms76]

One of my assumptions here is ATK didn’t put enough sealant on the split line joint. I’m skeptical of this for two reasons: a. It leaked near instantly. b.Had to fix three water leaks where they either did not apply sealant to the threads, or applied sealant too high on the thread where it didn’t actually seal the threads - like the #11 head bolt. So I’m almost thinking of pulling it apart, inspecting the lower seal and checking to see if they applied any sealant at all.

You’d think a rebuilt engine wouldn’t have a bad seal since the upper is installed prior to the crank. Unless installed backwards, which I doubt or it would probably leak a bunch more. The lower seal would be hard to damage.

I’m really think the seal is fine, just too little or no sealant applied on split line resulting in a small leak.

Switching to Castrol GTX high mileage which is a slightly thicker high mileage oil solved my small leak.

Originally used 10W-30 pennzoil high mileage conventional. Leaked. Now using Valvoline Max life semi-synthetic and seems to leak a little more. Definitely think it is slightly thinner as oil pressure is still very good, but slightly lower when hot at idle. Do you think the Castro GTX is thicker than the conventional pennzoil 10W30 high mileage? Seems like all synthetic blends are going to be thinner. Pennzoil was the only high mileage that was strictly conventional that I could find.

I have not attempted to use anything heavier like 10W-40. Any thoughts or experience with that. Have done some research, but see many mixed things about it. Everything from caused major engine issues to made engine run great. So, have avoided that path.

 

[Claybirdd]

Originally used 10W-30 pennzoil high mileage conventional. Leaked. Now using Valvoline Max life semi-synthetic and seems to leak a little more. Definitely think it is slightly thinner as oil pressure is still very good, but slightly lower when hot at idle. Do you think the Castro GTX is thicker than the conventional pennzoil 10W30 high mileage? Seems like all synthetic blends are going to be thinner. Pennzoil was the only high mileage that was strictly conventional that I could find.

I have not attempted to use anything heavier like 10W-40. Any thoughts or experience with that. Have done some research, but see many mixed things about it. Everything from caused major engine issues to made engine run great. So, have avoided that path.

When I tried valvoline it leaked the worst. Try the castrol and give it a month. Some oil additives counteract other brands additives. As an example I had used castrol for several changes and when I switched to valvoline it began leaking because their additives broke down the seal conditioning that castrol uses and it leaked pretty bad. Took a few weeks for it to seal up again and then when I changed back to castrol the next oil change it did the same thing.