Rear Main Seal Replacement (4.0)

Unless your RMS is leaking an abnormal amount of oil I would not get all paranoid and be in a rush to replace it. The one in my XJ started to leak around 100k and was still leaking at 213k when I sold it; never replaced it. That being said I did keep an eye on oil levels but a couple of drops a day will not take you out of the game.
 
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chino1969 said:
Unless your RMS is leaking an abnormal amount of oil I would not get all paranoid and be in a rush to replace it. The one in my XJ started to leak around 100k and was still leaking at 213k when I sold it; never replaced it. That being said I did keep an eye on oil levels but a couple of drops a day will not take you out of the game.
Click to expand...

Oh it’s really bad. Like puff off smoke behind me the entire time driving
 
There are jobs I will do and others will go to a trusted shop. My days of laying on my back with lights, rust falling down and fucking misery are over. I'm too old for some of that shit. If I had a lift I would probably do quite a bit of work but I don't and my ass bones and bones, in general, hurt too much when pushed too hard.
 
chino1969 said:
There are jobs I will do and others will go to a trusted shop. My days of laying on my back with lights, rust falling down and fucking misery are over. I'm too old for some of that shit. If I had a lift I would probably do quite a bit of work but I don't and my ass bones and bones, in general, hurt too much when pushed too hard.
Click to expand...

I really wanted to have a shop do this. Sadly I think this motor is ending near end of life so I thought I would try. It has a knock and I see part of the piston skirt in the oil pan. I’m hoping to finish this job then see how long it lasts while I save for a new motor haha
 
Chappys4life said:
I really wanted to have a shop do this. Sadly I think this motor is ending near end of life so I thought I would try. It has a knock and I see part of the piston skirt in the oil pan. I’m hoping to finish this job then see how long it lasts while I save for a new motor haha
Click to expand...
Try a flat point punch. Be sure to hit the part of the seal with the metal in it. But be careful not to damage the block the right size punch is important.
 
Finally got it out! Also was able to get the new seal in, torqued the main cap, and put back in the main bearing support.

Tonight it’s clean the oil pan and block area and install it. Have to get a new starter and battery terminal. The bolt for the 12v connection on the starter was frozen so I cut the cable. Making a new 2 gauge cable and the replacing the terminals as they look like crap.
 
Buttoned up the motor today. That was a involved job.....

Sadly still leaking some when parked. Doesn’t look bad but it was also masking a auto trans leak. Pulling it next
 
Chris said:
View attachment 2557

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.)
View attachment 2554

Rear Main Seal (2 pieces)
View attachment 2555

Oil Pan Gasket (Click on the image to see the part number.)
View attachment 2556

Some instruction that were included in the oil pan seal and the rear main seal.
View attachment 2559

View attachment 2558

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.
View attachment 2561

2. Drain the engine oil. I have SureDrain by Fram installed on the oil pan.
View attachment 2560

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.
View attachment 2562 View attachment 2563 View attachment 2564 View attachment 2565 View attachment 2566 View attachment 2567

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.
View attachment 2568

5. Remove the main bearing cap brace by removing 12 bolts. This is the long stick shown in the following picture.
View attachment 2569

6. With the main bearing cap brace removed, remove the rear main bearing cap.
View attachment 2570 View attachment 2571

You will have to wiggle the cap loose front to back, not side to side.
View attachment 2572 View attachment 2573

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.
View attachment 2574 View attachment 2575 View attachment 2576

Here is what they look like removed from the engine. The top half and the bottom half is shown here.
View attachment 2577 View attachment 2578

Notice how the old seal has lost its shape. *Blue residue shown on the new seal is wheel bearing grease.
View attachment 2579

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
View attachment 2580 View attachment 2583

After
View attachment 2584 View attachment 2585

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.
View attachment 2582 View attachment 2581 View attachment 2586

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!
View attachment 2587

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.
View attachment 2588

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.
View attachment 2589

Here is how they should look after you are done cleaning.
View attachment 2590 View attachment 2591

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.
View attachment 2593

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.
View attachment 2592 View attachment 2594 View attachment 2595 View attachment 2596

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.
View attachment 2597

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!!
View attachment 2598 View attachment 2599 View attachment 2600

*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.
View attachment 2601

13. Install the bearing brace and torque the bolts to 35ft.lbs.
View attachment 2602

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.
View attachment 2603 View attachment 2604 View attachment 2605 View attachment 2606 View attachment 2607

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 the bolts to 84in/lbs for the 1/4" bolts, and 132in/lbs for the 5/16" bolts.
View attachment 2608

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.
View attachment 2609

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.
View attachment 2610 View attachment 2611

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...
I just came across your post Chris. Thanks for putting this out there. I'm tackling my leaking seal this Saturday. You've just made this much easier for me!
 
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Just thinking out loud here, but where would you all rank the difficulty level of this job on a scale of 1 to 10? My jeep is leaking pretty decent amount and I'd like to get it fixed without having to pay $600.

My main concern is getting the existing seal out without damaging anything.
 
Depends on your technical abilities and how comfortable you are with tools. I re-did my rear main seal under 4 hours and that was taking my sweet time. I did mine in my driveway while laying on my back to do the job. I'd say between a 6/7 out of 10. Hardest part was removing the exhaust. The rest is straight forward.
 
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I am getting to where I need to fix mine. I agree with most everyone on laying on my back with oil dripping in my face. I see the prices and quotes on here to have a shop fix it, but I can’t find anything close. I live in Phoenix and of course my Jeep has spent its life here, so underbody rust is at a bare minimum, but still I have not been quoted anything under $1000 to replace my RMS. Out of 4 shops that came recommended, 3 were between $1100 and $1250 and one at $1000. Is it just a Phoenix or is there a code here in PHX I don’t know. Jeff
 
Chris said:
View attachment 2557

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.)
View attachment 2554

Rear Main Seal (2 pieces)
View attachment 2555

Oil Pan Gasket (Click on the image to see the part number.)
View attachment 2556

Some instruction that were included in the oil pan seal and the rear main seal.
View attachment 2559

View attachment 2558

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.
View attachment 2561

2. Drain the engine oil. I have SureDrain by Fram installed on the oil pan.
View attachment 2560

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.
View attachment 2562 View attachment 2563 View attachment 2564 View attachment 2565 View attachment 2566 View attachment 2567

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.
View attachment 2568

5. Remove the main bearing cap brace by removing 12 bolts. This is the long stick shown in the following picture.
View attachment 2569

6. With the main bearing cap brace removed, remove the rear main bearing cap.
View attachment 2570 View attachment 2571

You will have to wiggle the cap loose front to back, not side to side.
View attachment 2572 View attachment 2573

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.
View attachment 2574 View attachment 2575 View attachment 2576

Here is what they look like removed from the engine. The top half and the bottom half is shown here.
View attachment 2577 View attachment 2578

Notice how the old seal has lost its shape. *Blue residue shown on the new seal is wheel bearing grease.
View attachment 2579

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
View attachment 2580 View attachment 2583

After
View attachment 2584 View attachment 2585

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.
View attachment 2582 View attachment 2581 View attachment 2586

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!
View attachment 2587

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.
View attachment 2588

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.
View attachment 2589

Here is how they should look after you are done cleaning.
View attachment 2590 View attachment 2591

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.
View attachment 2593

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.
View attachment 2592 View attachment 2594 View attachment 2595 View attachment 2596

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.
View attachment 2597

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!!
View attachment 2598 View attachment 2599 View attachment 2600

*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.
View attachment 2601

13. Install the bearing brace and torque the bolts to 35ft.lbs.
View attachment 2602

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.
View attachment 2603 View attachment 2604 View attachment 2605 View attachment 2606 View attachment 2607

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 the bolts to 84in/lbs for the 1/4" bolts, and 132in/lbs for the 5/16" bolts.
View attachment 2608

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.
View attachment 2609

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.
View attachment 2610 View attachment 2611

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...
Mike_H said:
Yup, that is where I got mine too.
Click to expand...
First off I just want to say thank you for spending the time to put this tutorial together. Excellent directions along with the photos.

After completing the steps I thought I nailed it...The Jeep did not leak after filling it with oil and driving it around the block. Although today I drove about 50 miles and noticed is was leaking again. I did “shaved” a razor thin of material off the inside rear seal as I carefully inserted it. Could this be the problem to the leak?
Steve
 
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