Rear Main Seal Replacement (4.0)

David Smith said:
I got it out. Finally figured out the proper move back and forth technique.
Click to expand...
Well, it is out but now having trouble getting the seal out. After reading some.other advice on another site, I think I may have damaged my bearing. Instead of rocking side to side, I was rocking it front to back. See the attached image. Notice the shiny spots at the front and back of the bearing. Did I damage it?

https://photos.app.goo.gl/n99kSePouSRxDvhk9

IMG_20180623_133812.jpg
 
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Chris said:
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When the time came for me to replace the leaky rear main seal on my TJ, I searched online for a decent write up. Some of them were ok, but none of them were good enough to really show the potential DIY to see what is really going down with the repair. Besides many were lacking crucial details, explanations and/or without pictures. I decided to bring something that is more than a write up with 5 pictures. You won't be disappointed with the amount of detail shown in this write up.

Anyhow, chances are, if you own 4.0L I6, you will have a rear main seal leaking on you. As shown in the picture above, the symptom is a engine oil leak between the engine and the transmission. This repair costs anywhere from $300 to $600 depending on where you get the repair done. Surprisingly, all the parts only cost around $50. Not saying it is easy to do, but this repair is not all that hard to do it yourself. With the this guide available in DDTJ, you will know exactly what you are getting yourself into as usual.

Tools and Parts Needed

Here are the pictures of the parts you will need to hunt down.

Anaerobic Gasket Maker (it cures when there is no oxygen.)
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Rear Main Seal (2 pieces)
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Oil Pan Gasket (Click on the image to see the part number.)
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Some instruction that were included in the oil pan seal and the rear main seal.
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Job Hours
Takes about 2-6 hours.


Procedure
1. Remove the oxygen sensor from the down pipe. Remove the bolts and nuts holding the down pipe to the header. You will have to move the pipe around so that you can lower the oil pan later.
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2. Drain the engine oil. I have SureDrain by Fram installed on the oil pan.
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3. Chrysler used different sized bolts to hold the oil pan to the engine block. I think they used 1/2 inch and another size. I took several pictures of the bolts and where they are located so I don't I have to remember them where they go back. Here they are, for your reference. Start removing them and put them in a safe place.
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4. Once the oil pan is out of the Jeep, this is what it looks like. Your engine may look different with less brown. My Jeep is 10 years old, JFYI.
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5. Remove the main bearing cap brace by removing 12 bolts. This is the long stick shown in the following picture.
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6. With the main bearing cap brace removed, remove the rear main bearing cap.
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You will have to wiggle the cap loose front to back, not side to side.
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7. Remove the top half of the seal by driving it out of the block. Use extreme caution not to score/dent/scratch anywhere. One small nick or scratch can cause leak and is no longer repairable. As you remove the seal, note the orientation of the seal. The seal is opening towards the front of the vehicle.
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Here is what they look like removed from the engine. The top half and the bottom half is shown here.
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Notice how the old seal has lost its shape. *Blue residue shown on the new seal is wheel bearing grease.
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8. Start cleaning the mating surfaces. Make sure things are cleaned down to the metal without removing any metal. I used old tooth brush with a lot of elbow grease. Make sure there is no oily residue left. This is ABSOLUTELY CRUCIAL for the success of this repair. One little residue of old sealant will cause leak. Oiled surface does not allow the adhesive to adhere properly. I used a paint prepping agent to clean the surface. Pay particular attention to the areas indicated by the arrow.

Before
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After
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While you are cleaning the bearing cap, if the bearing falls out of the cap, put it back on the cap with a bit of grease to go between the two pieces. It only goes in one direction.
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Clean the engine block where the bearing cap mates against free of any residue whatsoever! This cannot be stressed enough! Clean ANY mating surface ABSOLUTELY free of any old sealant and any type of residue!! Remember you have to do this WITHOUT damaging/scoring the metal!
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This is a picture of two pieces of paper towels. Left one is used to absorb the oil from the bottom of the oil pan. The one on the right is virgin oil. There was considerable amount of solid stuck on the bottom of the oil pan.
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9. Start cleaning the oil pan. Remove the old gasket and clean the mating surface with mild wire wheel. I cleaned the surface with paint prepping agent once again. this gets rid of any oil residues left behind.
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Here is how they should look after you are done cleaning.
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10. Install the upper half of the seal after lubing with some engine oil. DO NOT PUT ANY SEALANT ON THIS SEAL! With the seal's lip opening towards the front of the vehicle.

*Here is one crucial detail that every online write up fails to emphasize. As you push in the upper half of the seal, if you do not follow (as you push the seal) the circle channel carefully, you will cut the seal and this will guarantee the rear main seal to leak again.
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So how do you install the upper seal without cutting it up? Fel-Pro included this nifty thin plastic that you wedge between the channel and the seal to keep it from getting cut. *I saw the same seal kit that included this plastic piece, and some did not. Your mileage may vary.
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Notice the orientation of the seal where the mouth of the seal opens toward the front of the vehicle. Once seal is in place, simply pull the plastic out.
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11. Start applying Chrysler Anaerobic Sealant or Loctite 518 on the rear main bearing cap mating surfaces as shown in the following picture. You DO NOT NEED MUCH. It is CRUCIALthat you DO NOT get any of this sealant on the lip of the seal! Make sure you compensate for the spread of the sealant once it is jammed between the surfaces. Put some engine oil on the bearing!!
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*Anaerobic Sealant starts curing after when it is isolated from the atmosphere unlike most RTVs. Some may say they got away with using RTV. They got away. I am not sure if you will. I also noticed the anaerobic sealer had different viscosity compare to the red RTV that I used on the oil pan gasket. BTW it is the factory service manual that is calling for this Loctite 518 or equivalent. There is no Loctite 518 available in the local part store which is the anaerobic sealant. You will have to get this sealant from the dealer.

12. Install the main bearing cap and torque the bolts to 80ft.lbs.
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13. Install the bearing brace and torque the bolts to 35ft.lbs.
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14. Place the oil pan gasket on the pan. I used RTV on the crucial area at the front of the block and where the rear bearing cap. I can use RTV here, because this is to seal something that is not moving against anything. Notice that I used RTV on both the top and the bottom of the oil pan gasket. *MAKE SURE YOU CLEAN THE MATING SURFACE OF THE ENGINE BLOCK FREE OF ANY SEALANT AND OILY RESIDUE! I used paint prepping solvent to clean the surface.
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15. Install the oil pan but while doing so make sure the rear main bearing cap's groove lines up with the oil pan gasket. Also pay particular attention to gasket on the front of the engine. It has built in grooves that has to sit just right. Tighten all the bolts and nuts to 12ft.lbs.
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16. Install the down pipe back on the header and install the oxygen sensor back on the down pipe and JUST hand tight it down. It just needs to be on there tight enough so it won't fall back out on its own.
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17. Replace the oil filter and put in 5qt of oil and watch the dip stick to top off. *I learned my jeep even tough it was almost bone dry (which I left it to drain for two days while I was working on the rear end.) it did not take the full 6qts. More like 5 and 1/2 qts total to have it read "Full" on the dip stick.
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18. Enjoy leak free engine! No more oil spots on the driveway! Pat yourself on the back, you saved a few hundred dollars!
Click to expand...

Thanks Chris! Great info, no drips on my “new to me” 03 but am seeing signs of doing thin in the future.Excellent article.
 
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cliffish said:
I am not complaining about what he wants to charge ,as a business owner myself, I am fully aware that everyone is supposed to make a profit in their business. I gazed at it under the lift and walked away last weekend.....it would probably take me 10 hours and a bunch of bitching and moaning. The write ups make it look much easier than it is....especially on a Northeast Jeep, my 81 corvette rear main seal was a breeze compared to this and on that I had to drop the front steering components.

My main question was does the starter also have to be dropped? as that is not mentioned in most of the write ups I have seen.
Click to expand...
We don't drop the starter as a matter of course unless it is in the way of something. I don't think it has to be out of the way for the oil pan to come down.
 
David Smith said:
Well, it is out but now having trouble getting the seal out. After reading some.other advice on another site, I think I may have damaged my bearing. Instead of rocking side to side, I was rocking it front to back. See the attached image. Notice the shiny spots at the front and back of the bearing. Did I damage it?

https://photos.app.goo.gl/n99kSePouSRxDvhk9
Click to expand...
Should be fine.
 
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David Smith said:
Well, it is out but now having trouble getting the seal out. After reading some.other advice on another site, I think I may have damaged my bearing. Instead of rocking side to side, I was rocking it front to back. See the attached image. Notice the shiny spots at the front and back of the bearing. Did I damage it?

https://photos.app.goo.gl/n99kSePouSRxDvhk9
Click to expand...
I find it doubtful that what you're seeing is the result of your removal technique, nor do I consider that damaged. Hard to tell from a picture, but if it feels smooth, and you're not planning on doing rod and main bearings, I would not hesitate to reinstall that bearing. That's just my opinion. Do with it what you will. ;):)
 
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I am knee deep in this project and the instructions have been very helpful.
When I removed the nuts on the bearing cap, both studs came out with the nuts.
This brings back bad memories of a '72 VW Bus with stripped exhaust manifold studs that I once owned.
Should I leave the nut on the stud and just screw them back in and torque or should I separate them and put the studs in first?
I suppose I can double nut the stud and put it in but what there is probably a torque spec for that and I don't know what it is.
Any suggestions?
Thank you.
 
Well, I got everything back together and buttoned up but I definitely did something wrong because I'm leaking a lot of oil now.
It was a difficult job to do on my 50-year-old back. I'll give it a day or two and see if I want to do it again or take it to a shop.

Is there a common mistake that is usually made by weekend mechanics when they try to do this?
I'm starting to think it has something to do with the different seals that were used.
There is the one with the flange on the bottom half and the one without a flange.
The seal that I removed did not have a flange, nor did the new one that I put in so maybe that aint the problem....
I did not damage the seal when I installed it.
 
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Chris said:
That's because there are two rear main seals, one for earlier model 4.0s and one for later models (as mentioned in the original post):
Now I can't actually comment on this first hand as I've never worked on an earlier model TJ, but it seems to make sense.

The 2000-2006 model rear main seal in the original post is the same one you just linked to in your post.
Click to expand...

I believe this could become a source of confusion for someone trying to do this.
The original post does not mention the year of the vehicle being worked on. It just says it is "ten years old." Since the post is from 2016 I assumed the Jeep is an '06.
The author also mentions that he has "never worked on an earlier model TJ..."
The pictures in the original post, however, show the seal for a '97 - '99 model.

And, just like every other guide or video I found on the subject, this one kinda glosses over what a pain in the neck it is to remove the exhaust. This, by far, is the most difficult part of the job, in my opinion. I am working on a 2002 TJ. Maybe other years are easier.

My first attempt at this job was unsuccessful. When I buttoned everything back up it leaked worse than when I started. At this point, I checked with a couple of local shops to see how much it would cost to have it done. Best price I found was $823 plus parts. I live in the San Francisco Bay Area where everything seems to be more expensive than the rest of the world. I would have gladly paid $500 plus parts to have someone else do it but $823 plus parts was beyond my budget so I am doing it again.

I'm still not exactly sure where I went wrong the first time around. I have a feeling it has something to do with the different seal. The earlier model, the one with the flange on the bottom half, seems like it would be easier to do.
There was a small piece of paper that came with the oil pan gasket that said I am supposed to fill that gap with rtv????
Why did this information come with the oil pan gasket and not with the RMS?
 
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I happily paid my mechanic $417 to replace the RMS and oil pan gasket. It was done in a day and with a guarantee to fix it if it leaked again.

Too many stories like the one above with things that go wrong or leaking again immediately.
 
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This job sucks, If I did it once and leaked, I would then pay a pro to fix it...hell I might pay a pro to do it the first time....I could not budge the cat bolts even with kroil...I don't want to snap those.
 
cliffish said:
This job sucks, If I did it once and leaked, I would then pay a pro to fix it...hell I might pay a pro to do it the first time....I could not budge the cat bolts even with kroil...I don't want to snap those.
Click to expand...
Come on now, it's not that hard at all. The cat bolt is cheap, just sawzall cut it and replace them new.
The hardest is to remove the oil pan through the exhaust looped around under, but if you figured that out, piece of cake.
 
The Shop cost is about 500.
You can buy a nice Milwaukee cordless impact for around 250-350 at homedepot. (My 2nd favorite tool) it has saved me so much time on everything. Rusted bolts come off like a dream. I have found that the Milwaukee out preforms my air impact. And i don't have to drag around an air hose.
Even at the 350 dollar price you are still ahead on money and you will have a great tool for your jeep.
 
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I have cordless impact wrench that can easily snap the bolts...Remember I am in NY not AZ we have rust here on every bolt.
TJ2 I am talking about the 2 precats that are right under the manifold I need to disconnect to get the exhaust out of the way to drop the oil pan.
 
cliffish said:
I have cordless impact wrench that can easily snap the bolts...Remember I am in NY not AZ we have rust here on every bolt.
TJ2 I am talking about the 2 precats that are right under the manifold I need to disconnect to get the exhaust out of the way to drop the oil pan.
Click to expand...
You are talking about the manifold, not the cat. That is totally different spot.
Now, you can remove the oil pan without unbolting the manifold.
A gear-head buddy of mine thought me how to do it in his shop.
 
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