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Rear Main seal preference?

LJRockstar

NAXJA Forum User
A few months ago I did the rear main seal in my 96 4.0
It has started to leak again. I’m fairly certain it’s because the wrong sealant was used where the two halves of the seal meet. But it could be a bad part. I used a Fel-Pro seal the last time.

Do any of you have a preference for another brand? Or bad luck with any particular brand? I don’t want to do this job a third time in a few months when there’s snow on the ground....
 
I used Fel-Pro on two engines about 10 years ago and no problems. I assume you've checked and it's not coming from above and the crankcase vent isn't plugged up.
 
I used felt pro when I did mine. As Lawsoncl says, make sure it’s not from somewhere else like the valve cover gasket.

It’s real easy to get one part of the seal in backwards.
 
Thanks guys... I’m sure it’s the rear main. Was under there yesterday and everything is nice and dry except right around and below the rear main area. Gonna grab a new seal and pan gasket tomorrow. Hopefully I have time next weekend to do the job.
 
What sealant did you use?


Looking at the FSM, they specify "Mopar Gasket Maker", which looks pretty pricey: https://www.amazon.com/Genuine-Chrysler-Accessories-4318083-Gasket/dp/B00BV4DH4A


I'm about to do the rear main on my '98 XJ next week, and was going to use Permatex 51817: https://www.amazon.com/dp/B000A7DG3G/ref=psdc_15719581_t1_B00BV4DH4A?th=1


I also ordered the Fel-Pro BS40612 seal. Reading through walkthroughs and watching YouTube videos, it seems like people often use too much sealant and in the wrong places. The '99 FSM just recommends two dots on the cap and two on the block.
 
What sealant did you use?


Looking at the FSM, they specify "Mopar Gasket Maker", which looks pretty pricey: https://www.amazon.com/Genuine-Chrysler-Accessories-4318083-Gasket/dp/B00BV4DH4A


I'm about to do the rear main on my '98 XJ next week, and was going to use Permatex 51817: https://www.amazon.com/dp/B000A7DG3G/ref=psdc_15719581_t1_B00BV4DH4A?th=1


I also ordered the Fel-Pro BS40612 seal. Reading through walkthroughs and watching YouTube videos, it seems like people often use too much sealant and in the wrong places. The '99 FSM just recommends two dots on the cap and two on the block.

I don’t even know what it was. I had the seal in the glovebox and had the Jeep up on a friends lift working on some completely different stuff. He noticed how oily everything was and we started tearing the pan off. It wasn’t till it was way too late on a Sunday that we realized all there was in the shop was an old tube of some orange stuff. Had to fold and squeeze the tube like when you’re trying to get one more day out of a tube of toothpaste haha. Being it’s my DD and I had to get to work in the am we did what we could and put it back together... now I’m paying the price by doing it again. Personally my go to sealant is the red Yamabond stuff. It’s never failed me. It’s made by LocTite. Number 518. Loctite 518 50ml Red Gasket Eliminator Tube https://www.amazon.com/dp/B000FONONG/ref=cm_sw_r_cp_api_C8lCBbG2T1C4TI’m sure if I had that on hand I wouldn’t be doing it again.
 
Haha, old mystery sealant sounds like the culprit for sure.


Interesting you mention Loctite 518, as I went back to the '98 paper FSM I have, and that recommends using Loctite 518. It also has a different sealant pattern shown on the bearing cap (I'd post pictures but this forum doesn't allow attachments?), short beads on the outer edge instead of dots. Based on the figures, it seems like the bearing cap style changed from '98 to '99, and who knows if it's the same as your '96.

Reading through the Loctite 518 instructions, it mentions requiring Loctite 494147 activator sprayed on before application. I went back and checked the Permatex instructions, and sure enough it needs an activator spray as well, Permatex 24163, which clocks in at $20 - ouch!
 
I’ve never used the primer and have had excellent results in the past. Years ago I worked in a Yamaha dealer during the big RoadStar recall. I had the cases apart on nearly 100 of those things. Never had one come back with a leak. That being said, I’ll give it a try this time. I wanna give it the best possible chance I can. Haha
 
So I've been reading about anaerobic sealers for the last 30 minutes, and I've come to the conclusion that the activator spray is NOT required, despite the wording on the sealant.


In this post, the guy called Permatex for clarification: https://www.jeepforum.com/forum/f13/anaerobic-sealer-activator-2761290/#post25969770


And their response agrees with other things I've read, which is that the spray is only necessary on surfaces that allow for air to come into contact with the sealant (porous surfaces). Two machined metal surfaces with low clearances like what we have with the bearing cap would not need the activator spray.
 
Whew, glad I caught you in time! I'd have felt bad making you waste $20 based on my incomplete research.


Good luck with your install. I'll probably tackle mine next weekend. :cheers:
 
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