Engine: Rear main Leak

[steve.maclean2009]

Hi everyone,

I have a rear main seal leak in my 259 engine that we finished rebuilding. Story is my dad started assembly including installing the rear main on engine 10 years ago. He passed away 3 years ago and I finished assembly on it recently. It has new pistons, rings, crank, bearings, etc, When I started it up it was leaking from rear main. I took it out (with engine in the car) by taking the cap off and then pushing the old seal out. It came out really easy. I put a new one in and it's leaking as well. I was watching a video that R1Lark created on you tube and he was talking about how some of the new seals don't have a snug fit. I am wondering if this is the reason it's leaking. He suggested putting a bit of RTV inside the seal. I was also watching the Jim Maxey videos and he put RTV on the inside of the new seal before installing it and installing the crank, and cap.

I would like to try using a bit of RTV on my seal and hopefully fix the leaking issue. My question is if I put some RTV on the inside of the seal and then install the seal by pushing it around the crank, will the RTV that I put in the seal get pushed out by the part of the block the seal sits on? Or will there be enough RTV in there after it's installed to make a tight fit? It won't be an issue with the cap because the seal will just slide on. This wouldn't be an issue if the crank has been removed but that's another can of worms I don't want to get into.

Thanks!

Steve

[Squatch]

I personally have had very little success solving problems with RTV. Especially when you must work in a space where you may not be able to remove ALL traces of oil before applying it.

If you are sure that the seal is leaking around it, and not through the seal/crankshaft interface then this is what I'd do. Consider this my opinion, not necessarily advice.

I would proceed by loosening the main bearing caps in the rear, and at least the one adjacent to it. You need the crank to drop a few thousandths. Then, clean the entire seal area with brake cleaner and compressed air. Clean the seal as well. Then apply a small amount of old-fashioned Permatex Form-a-Gasket or gasket shellac. (I swear they're the same thing, except the shellac is thinner. I may be wrong.) While it's still fresh, retighten the main bearing caps and leave the oil pan off for at least a day to aid in drying.

Be warned, if you do this and it fails, you'll be disassembling the engine. Both of those products set up pretty hard.

[StudeRich]

Do understand that No One is suggesting putting ANY Sealant on the Seal Surfaces of the two Seal Half's, just a LIGHT coat on the back where they mount and they Ends to "glue" them together.

Also be sure you have the Tiny, Corks into the groves in the Block and sides of the Rear Main Cap, THEN the Tabs on the ends of the Pan side gaskets, then the rear Arch Cork Gasket for the Pan.

It is just as important to properly seal the Pan as it is the Rear Main to prevent leaks that are sometimes hard to tell WHICH it is leaking.

All of the above, lightly coated with your favorite Sealant.

[yeroldad]

Another thing to check/do is put the seal in WITHOUT lining up the seal ends, put them in where the seal ends are not lined up with the block, with one sticking out a bit, like a quarter inch or so, and the other end up into the block about 1/4 inch up in the block. Put the other seal in to match up with the offset lining up with the other seal. Many times, if the seals are lined up with the block and main cap where they come together, it has a propensity to leak where the seals come together. I don't put the "corks" in. I assemble the main cap and then fill the cork area with ultra silicone and let it dry, cut off the excess so that it is even with the block, a skim of silicone on the pan gasket, and put it on. I never had a leak doing it that way, and I have built many many motors in the 50+ years I've been wrenching. Of course, ya gotta have the right seal. I've seen people put the seal in backwards, with the lip outside instead of it being on the inside, where it should be, and it will leak, and leak a lot. Make sense?

[jackb]

Just a question: Will the cork pan gaskets change their alignment/fitment after just sitting all that time ? Did you/will you replace the old cork gaskets as a part of this newer fix ? Chime in please.....

[altair]

Just be sure it is not running down from the valve covers.

[steve.maclean2009]

Just a question: Will the cork pan gaskets change their alignment/fitment after just sitting all that time ? Did you/will you replace the old cork gaskets as a part of this newer fix ? Chime in please.....

Yes I have a new oil pan gaskets and cork. It gets expensive trying to fix the leak having to put new cork and gasket in every time I test for the leak.

[steve.maclean2009]

Just be sure it is not running down from the valve covers.

Yes I checked that. It's not from the valve covers.

[steve.maclean2009]

Another thing to check/do is put the seal in WITHOUT lining up the seal ends, put them in where the seal ends are not lined up with the block, with one sticking out a bit, like a quarter inch or so, and the other end up into the block about 1/4 inch up in the block. Put the other seal in to match up with the offset lining up with the other seal. Many times, if the seals are lined up with the block and main cap where they come together, it has a propensity to leak where the seals come together. I don't put the "corks" in. I assemble the main cap and then fill the cork area with ultra silicone and let it dry, cut off the excess so that it is even with the block, a skim of silicone on the pan gasket, and put it on. I never had a leak doing it that way, and I have built many many motors in the 50+ years I've been wrenching. Of course, ya gotta have the right seal. I've seen people put the seal in backwards, with the lip outside instead of it being on the inside, where it should be, and it will leak, and leak a lot. Make sense?

yeroldad What do you do with the spaghetti ends of the part that goes in the cap? Do you cut them off and then place them in the grove and use sealant to hold them in place?

[altair]

Just another point, when the cork gaskets are installed they firstly appear to be too long and many people trim them, they must be compressed and usually require some finesse to install them. This usually requires four extra long bolts in each corner and gradually pull them up evenly to compress the cork, then when close enough install the regular pan bolts. With my engine out it took me at least 45 minutes to install the pan.

[yeroldad]

Steve; Cut them off and fill the groove with Ultra Black silicone. Do not put a excessive amount on there, ya don't want it goozing all over, and make sure there is absolutely no silicone on the lip, where the seal contacts the crankshaft. Just enough to be sure the silicone contacts the main cap/block. And a bit where the outside of the cap fits into the block, which is another potential leak area. And, needless to say, it all has to be squeaky clean, or the silicone will not be able to do it's job, stick. Let the silicone dry completely before turning the crankshaft, I let it set for a few hours, or even overnight, depending on ambient temp . Of course, you want some assembly lube on the journal, but no so much that it goozes into the silicone. I put just a little on the centerline of the journal. When the cap is tightened up, it will squish sufficiently. I always have the spark plugs out and I crank the motor over until I see it has decent oil pressure before starting.

[Dwain G.]

I've heard the new Fel-Pro seals do fit a bit loose. Buy the seal Sandy Olson sells.

https://www.olsonsgaskets.com/?s=Studebaker+rear+main+seal

[StudeRich]

This needs clarifying, I heard it just the other way around !

A "New Type/Style" Seal on the Forum was found to be too loose.
The Felpro has been an exact copy of the original Brummer Seal forever, it would be surprising that it is now failing.
Of course I understand that SOME things made in USA forever are now being made offshore, but now this TOO?

If they "look" different how could they do the same job as the Original Design?