The Official Rear Main Seal replacement thread

[ChargerBob]

Hey Bob. It has to be measured. Post #13 explains how.

Thanks, i know that, Ray Barton told me many of the mopar high nickel siamese blocks had a problem with the seal grooves in the block, he said they had been milled to deep and were offset in the opening, i was wondering if it was a common thing as to which side the seal groove was commonly offset, i have a mopar high nickel siamesed block that is giving me a seal issue.

 

[Stereolab42]

When all else fails, behold, the Mopar diaper:

Just get a Summit engine diaper and cut it to fit around the front of the trans. Attach using whatever bolts are convenient (typically the top two inspection cover bolts on the front, allows you to easily drop that part to check leaks). Obviously still not a good idea if you have a serious leak, but if you are only leaking a few drops of oil from the rear main after a drive, like my cars do, then whatever.

 

[Nevada dan]

I like the old rope seal , they never leak , ever , they say you can loose a fraction of a horsepower though

 

[Sinitro]

Correcto...
The rope seals are still available..
But now they are made without asbestos, and don't seem to seal as well as the older versions..

Just my $0.02...

 

[440 Charger]

View attachment 405860

So bottom line leak or not lol.

 

[440 Charger]

Correcto...
The rope seals are still available..
But now they are made without asbestos, and don't seem to seal as well as the older versions..

Just my $0.02...

The the way world is now dont make good because it will last too long so make junk.

 

[khryslerkid]

We like to call it "Horsepower Sweat"

 

[themechanic]

So bottom line leak or not lol.

No leak. But they will all leak, eventually due to wear.

 

[dadsbee]

No leak. But they will all leak, eventually due to wear.

Engine in my Bee was rebuilt in 1978, main does not leak a drop and it hasn't been treated nicely in those 43 years.

 

[Nevada dan]

Engine in my Bee was rebuilt in 1978, main does not leak a drop and it hasn't been treated nicely in those 43 years.

they must have used a rope seal , they never leak

 

[RGC440]

Before you go to the trouble of replacing the seal, make sure that you are using a good PCV valve and a vented filler cap. Getting rid of the flat oil fill cap on my MP aluminum covers has solved the problem in both my 383 & 440 after the replacement of both did not slow it down.

I agree with the rope seal, but you must have the correct seal installation tool to properly form and seat it in both the block and retainer.

 

[2blader]

Would love to hear about more in the car rear main seal replacements in a Hemi. Have a Ray Barton engine that leaks. So it is an aftermarket block. So does the groove misalignment still exist in my block? I have two lower retainers. One blue anodized MOPAR piece that uses side seals and a Fast Fish unit with no side pieces and a one piece silicone seal that YOU cut on one side so that it stay in one piece as I am sure you guys are aware. I HATE rear main seal leaks and the car came with it. I tried the Fast Fish unit and it leaked bad but I think it was more my fault not being prepared doing it myself on a lift. Take it easy on me coming from BB Chevrolets. They tell you to put the seem at 12 oclock in the block. I am not so sure that is a good idea in the car as it is hard to see AND confirm the ends are square or touching as this seal is much more flexible. Also and I know this is not the way to look at it BUT the rear main seal area of the crank is 2.81xx in diameter. If I put the seal in the retainer and put a touch of pressure and measure the inside diameter it is just around 2.80. So I would have expected it to be a tad less to actually seal the crank. I guess what I am asking is how much is the seal actually pressed against the crank to seal it. Thinking maybe the grooves in the retainer and maybe the block are a tad too deep? Any guidance will be greatly appreciated Scott

 

[2blader]

Whelp took another shot at the leak which is not a dribble but something that keeps me from driving the car. Yup, it is that bad. This time I had everything ready cleaned written down etc. Nothing forgotten etc. Have the fast fish unit where you have a one piece seal and you cut it in one place. You are supposed to orient the cut at the 12 position but my Hemi is in the car. Pulled the rear main cap too. So I decided to put the seam at 6 oclock as I can control that much better. I noticed that seal fits snug in the groove in the block. Aftermarket Block I believe for a Barton engine. Anyhow, took the plugs out so I can turn the engine by hand to grease the seal area all the way around. Greases the one piece seal and put a very thin cote of the right stuff on the seal also and pushed it all the way through. Cleaned up any excess sealant before moving on. Took a touch of glue to glue the ends of the seal together. Then put the rear cap back on. Not to the seal retainer. I also put a .010 shim in the bottom since it seems like some seem to think the seal is not tight enough around the shaft. Took a tad of the Right Stuff in the retainer under and on top of the shim. Installed carefully to catch the seal correctly. Waited until this morning and it still leaked. Maybe not as much. 1 drip per 20 seconds. I also cut the block protector in half so I can see in there if needed. I did not install it before firing it up. I noticed it seems like most if not all of the oil is coming from where the starter is. I cleaned the block extremely well all the time so I can read where oil comes from. Last leak was the passenger side. Any ideas why behind the starter? What is back there if anything that can leak? Thanks Scott

 

[Fran Blacker]

What about putting seal seam at 4 o'clock so seal more likely pushing end together? Do they still make a number 5 main bearing that bleeds oil to the front of engine? There were grooves from front half of bearing almost to oil groove on the bearing.

 

[2blader]

What about putting seal seam at 4 o'clock so seal more likely pushing end together? Do they still make a number 5 main bearing that bleeds oil to the front of engine? There were grooves from front half of bearing almost to oil groove on the bearing.

At this point I am not sure the seam is the issue as I glued it flush before installing the retainer. There are grooves under the seal but not under the main cap. Just running out of options of what to do next. Have my sons car show this Saturday so I may just leave it for not and limp it there like it is.

 

[hunt2elk]

they must have used a rope seal , they never leak

I have to disagree with that statement. A shop had my motor all summer trying to fix a rear main leak. Replaced it 7 times and on the dyno 7 times. Finally he bough a $35 rope seal. Told me it was fixed. I put the motor back in the car, and it still leaks....

 

[2blader]

Whelp bought a rope seal and a sneaky pete. Just another option this week. I cleaned everything up again. and puta small spacer between the block protector and the block to make a space for the oil to drain. Started the car put it up on the lift and watched. It leaked on the passenger side and the driver side. The passenger side leaked quite a bit. The driver side only one drip the entire time it was running. It leaks the exact width of the retainer or the seal/ rank flange. I looked it over very well and could’t for the life of me see anything that I would have done different. So time to take it apart again. The seam I glued together stayed together until I removed the retainer. You heard it POP apart. Seal is still fine. The RTV is everywhere it is supposed to be and nothing had zero sealant. Have no friggin clue what is going on at this point. I know thee are oil galley plugs back there and just put a new clutch in. Every time it leaks it is worse on the passenger side of the crankshaft. It is nagging me about the galley plugs. I know it is a long shot BUT out comes the trans to check. I know I will be disappointed. Been there before. . I am getting pretty good at doing this too.

 

[Nevada dan]

The rope seal is not the leak your cap is binding when tightening, it happens a lot
Take the seals out and find where the cap is hitting

 

[Fran Blacker]

On factory seal holder the little nubs for oil pan bolts can hit #5 cap. I grind mine a little as a precaution. After market cap I'd check it.

 

[2blader]

The rope seal is not the leak your cap is binding when tightening, it happens a lot
Take the seals out and find where the cap is hitting

Hmmm not to sound dumb but what would the cap be binding on and how would that effect a leak? I install the seal into the block then install the rear cap then the lower retainer. So what do I have to look for as I have to be doing something dumb. How would I know the cap is binding at all? Pardon for the dumb question or is it a feel thing? Added a pic of the rear cap and the block plate. As you can see the leak is on the passenger side and has been every time. The kicker is it looks like the spot where the retainer meets the block BUT I have rtv’ed it every time there. Any ideas would be appreciated as I am trying to make my son’s car show this Saturday.