You are browsing the forum as a guest. Log in or register to access additional features. Forum Index

2189546 visitors since May 16, 2006
Register  ::  Log in Log in to check your private messages.

This forum is locked: you cannot post, reply to, or edit topics.  This topic is locked: you cannot edit posts or make replies.
 [Repair] Rear Main Seal Replacement « View previous topic :: View next topic » 
Author Message
PostPosted: Fri Mar 07, 2008 12:14 am    Post subject: [Repair] Rear Main Seal Replacement Reply with quote

Site Founder
Site Founder

Joined: 09 Apr 2006
Posts: 1769

[Repair] Rear Main Seal Replacement.


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

High Temperature RTV
Oil Pan Gasket (~$20)
Rear Main Seal (~$14)
LockTite 518 or Chrysler Part Number: 4318083 (Anaerobic! Not your average RTVs! It is not cheap but required, ~$16 from dealer. No parts stores carry this item.)
Paint Prepping Solvent
Sockets and Ratchets with extensions
Torque Wrench
6qts. of Engine Oil
Oil Filter

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

Anaerobic Gasket Maker (it cures when there is no oxygen.)

Rear Main Seal (2 pieces)

Oil Pan Gasket (Click on the image to see the part number.)

Some instruction that were included in the oil pan seal and the rear main seal.

Job Hours
Takes about 2-6 hours.

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.

2. Drain the engine oil. I have SureDrain by Fram installed on the oil pan.

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.

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.

5. Remove the main bearing cap brace by removing 12 bolts. This is the long stick shown in the following picture.

6. With the main bearing cap brace removed, remove the rear main bearing cap.

You will have to wiggle the cap loose front to back, not side to side.

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.

Here is what they look like removed from the engine. The top half and the bottom half is shown here.

Notice how the old seal has lost its shape. *Blue residue shown on the new seal is wheel bearing grease.

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.



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.

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!

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.

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.

Here is how they should look after you are done cleaning.

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.

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.

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.

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 CRUCIAL that 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!!

*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.

13. Install the bearing brace and torque the bolts to 35ft.lbs.

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.

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.

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.

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.

18. Enjoy leak free engine! No more oil spots on the driveway! Pat yourself on the back, you saved a few hundred dollars!


I tried my best to document as much as possible along with pictures. I hope you find them useful. However, do use the information provided here "as-is". or the author does not warrant or assume any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, or process disclosed. Use the information at your own risk.
Back to top
PostPosted: Sun Apr 06, 2008 1:33 pm    Post subject: Re: [Repair] Rear Main Seal Replacement Reply with quote


Joined: 06 Apr 2008
Posts: 1

Great write-up! wrote:
LockTite 518 or Chrysler Part Number: 4318083 (Anaerobic! Not your average RTVs! It is not cheap but required, ~$16 from dealer. No parts stores carry this item.)

I found Permatex anaerobic gasket maker at Advanced Auto for $6 (in a tiny little tube though).
Back to top
PostPosted: Wed Apr 09, 2008 2:54 am    Post subject: Reply with quote


Joined: 09 Jan 2008
Posts: 211
Location: Patterson, California

so just to clarify,

I am leaking some type of anti-freeze oil mixture.

Dealer told me it was freeze plugs by looking at it, but in the photograph that you have of this "Rear Main Seal Replacement", it looks IDENTICAL! I have a 4 cyl 2.5.

Is that what was leaking when you had to replace the rear main seal? A combo of antifreeze and oil?
Back to top
PostPosted: Wed Apr 09, 2008 12:44 pm    Post subject: Reply with quote

Site Founder
Site Founder

Joined: 09 Apr 2006
Posts: 1769

To answer your question, No.

If your freeze plug is leaking AND the rear main seal is leaking at the same time, I can see how they can mix outside of the engine and drip down towards the bellhousing of the transmission.

But if they are mixed in any shape or form inside of the engine, you have a serious problem.

IIRC, if you have 2.5L, you would have the rear main seal which I heard is not as easy to replace as 4.0L.

atjeep wrote:
I found Permatex anaerobic gasket maker at Advanced Auto for $6 (in a tiny little tube though).

To be honest, I called the local store around me and no one seem to know what I was even talking about.

Surprisingly, only my dealer part guy knew what I needed.

Thanks for sharing that! I will reflect that information in the write up.

Back to top
General Grant
PostPosted: Mon Sep 08, 2008 3:32 pm    Post subject: Instructions Used and Verified as Correct Reply with quote


Joined: 08 Sep 2008
Posts: 1

Excellent write up. The pictures and descriptions complimented the Chrystler Service Manual.

After my stock 1997 Jeep Wrangler 4.0L was introduced to a large rock in Colorado, my oil pan started leaking about a quart of oil per week. I searched some forums to get an idea of what was involved to replace the oil pan, and came across this post. After reading it through, I decided to replace my weeping rear main seal while I hand the oil pan off. I didn't realize it was so (relatively) easy.

Though the post indicates 2-6 hours of work, it took me a full Saturday and half of Sunday, due to other unforseeable problems (which may not be a problem for most Jeeps).
1) The nuts holding the exaust down pipe to the header were hard to get to, as well as incredibly corroded. I had to unbolt the front drive shaft at the differential, tie it up out of the way, and then try a combination of different wrenches and drives to break the nuts loose. The nut on the inner bend of the down pipe is especially hard to access.
2) The exaust joint between the catalytic converter and muffler was impossible to separate. In order to get the down pipe out of the way of the oil pan, I supported the transmission and took off the skid plate/rear engine mount, which allowed the whole exaust system to drop down a few inches.
3) My "original equipment Mopar" replacement oil pan (from Quadratec, $100) turned out to be 3rd party, and used a different size/thread for the drain plug. This was a problem for me, since I have a custom oil pre-lube system that has a banjo bolt pickup at the drain plug. Luckily, a real Mopar oil pan was in stock at Long Beach Chrystler Jeep ($190).
4) The top half of the rear main seal was solidly stuck in place. I was careful not to slip and score the engine block. Once the seal broke loose, it pushed/pulled out very easily.

I spent the rest of Saturday cleaning and prearing things for reassembly on Sunday. Sunday went much smoother. I took the author's advice and bought the official Mopar gasket maker ($18). I also used the NAPA Fel-Pro rear main seal and Fel-Pro oil pan gasket. Things went back together as planned. No leaks.

-- I had to LIGHTLY tap the rear main bearing cap to get it to break loose, after removing the bolts.
-- My Fel-Pro rear main seal did NOT include the protective plastic tab for installing the upper half. However, I was careful when pushing the new seal in, and followed the crank shaft closely. The seal should push in with hardly any resistance.
-- Let the engine drain for a while after removing the oil pan, prior to tyring to clean the gasket surfaces. Oil will continue to drip out of the block, undoing any sterilizing you just did.
-- The oil pan I ordered from Quadratec ($100) was made by Crown Automotive. After purchasing a real Mopar oil pan from the dealer ($190), I noticed a big difference in quality and craftsmanship. The Mopar oil pan has a nicer paint job and far superior drain plug (with a rubber flange) and threads in the pan (made of copper or brass). The one by Crown had a coarser threaded plug, a divorced metal flange, and steel threads in the pan. To me, the extra $90 was worth it for peace of mind and given the time constraints.
-- My Jeep took a full 6 quarts to top off. Still, you should monitor the dip stick for the last quart.
Back to top
PostPosted: Mon Nov 03, 2008 10:25 pm    Post subject: Reply with quote

I Helped!
I Helped!

Joined: 24 Feb 2008
Posts: 31
Location: St. George, Southern Utah

I wanted to say thank you very much for the highly informative and useful write up!
I would never have had the cajones to attempt this procedure without your excellent walk
A couple of notes for those out there that might have an auto trans (bleh) the dust shield that is directly behind the pan that protects the flywheel, is a total pain to remove but necessary, there are little tabs that keep the pan from simply dropping out. I say it's a pain only because the bolts are probably tighter than the ones on the bearing cap. Why that would be? I have no idea but it took a lot of effort to move them. Secondly, you won't have as easy access to the bolts along the passenger's side as that the tranny fluid lines run along the pan. Not a big issue by any means they are still plenty accessible. just FYI.
I also located some permatex anaerobic gasket maker at a local parts place, not sure if they are national, they are called parts-plus. Still 12-14 bones but it's another source. I read on another forum that Permatex and Loctite were subsidiaries until '99 and that their products are identical even their p#'s are similar, permatex is 51813, loctite's 51831.
Hope that helps someone.
Back to top
PostPosted: Wed Jun 17, 2009 12:06 pm    Post subject: Reply with quote


Joined: 17 Jun 2009
Posts: 2
Location: SoDak

Outstanding write-up! I was looking for info on OP gaskets and decided to do the rear main at the sametime when I found this. I couldn't ask for a better write-up! I would like to recommend PB blaster over night for rusty exhaust bolts. If you know you are going to do this plan ahead and spray them a couple of times while the exhuast is cool. Works wonders and keeps you from stripping the corners or breaking the bolt.
Back to top
PostPosted: Mon May 10, 2010 4:50 pm    Post subject: My '05 is a little different Reply with quote


Joined: 09 May 2010
Posts: 1

Great writeup, however my seal and seal cap seem to be a little different. Both upper and lower seals are indentical, therefor the lower one doesn't have those little straight tabs that come off it on each side. So I'm unsure where to put the RTV? I realize to put a dab on the seal ends where the two seals meet on each side, and I read somewhere else to put RTV on the chamfered edges of the cap. But I also read you shouldn't put RTV on the cap edge where it mates with the engine block because it can destroy proper bearing clearance. Is that true?

Back to top
PostPosted: Sat Jun 12, 2010 4:26 pm    Post subject: Main bearing torque specs Reply with quote


Joined: 28 Jul 2009
Posts: 10
Location: california

I just have one question. In your write up ,as well as others I've seen, it says to torque the main bearing caps to 80 ft/lbs. The haynes manual say's 80 inch/lbs. Is this a typo? this is a critical spec so I want to be sure it's correct.
Back to top
PostPosted: Sat Jun 12, 2010 7:11 pm    Post subject: Reply with quote


Joined: 28 Jul 2009
Posts: 10
Location: california

Nevermind. I looked again, time for new glasses! and btw, The hayne's manual is nowhere near as detailed as this write up!
Back to top
Display posts from previous:   
This forum is locked: you cannot post, reply to, or edit topics.  This topic is locked: you cannot edit posts or make replies. Page 1 of 1

Jump to:  

Jeep, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Daimler-Chrysler Corporation. is not associated with the Daimler-Chrysler Corp. in any way.
Copyrighted (c) 2006 - All right reserved.
Template Based on DAJ Glass (1.0.8) by Dustin Baccetti Logo Designed by Michael Kang
Powered by phpBB © 2001, 2005 phpBB Group