Rear main bearing seal - how is this supposed to be?

[Mastiff]

With my friendly, neigbouhood mechanic there's been a bit of work done to the turbo engine for my Oldsmobile Starfire today. But the upper part of the rear main bearing seal was kind of werid. It's a Fel-pro 73740, so not the rope type. Most of it was OK (even though he remarked that it's kind of weird that americans took so long discovering simmering seals.

But the weird part was the ruber "studs" that had to be pushed rather hard down in the holes, and then how the needles were to be used. He usually works on VW and Audi, so this part was pretty new to him. I have attached a photo of what it looks like. Are those needles just to be hammered down, or what? Don't mind the loose one and the angle of one of them, but are they to be put in like that?

 

[v6turbo87]

Don't use those seals. From the factory the side cavities were filled with RTV and that is what you should use. Here is a procedure I wrote on how to do a rear main seal:

http://www.gnttype.org/techarea/engine/rearmain.html

 

[Mastiff]

Aha, thanks a lot! Nice writeup! The shaft is already in, but do you recommend that we loosen it to put the seal off center? And what is the purpose of that trick?

Oh, and is it necessary to use RTV silicone, or is it possible to use regular gasket silicone? From what I saw on Wikipedia (I had to check, I didn't know the expression) it seemed like RTV is a special type of two component silicone. My mechanic has a brand he uses that he says is the world's best, and it's in a silicone gun, so it's easier to get down there.

 

[v6turbo87]

The purpose of rotating the seal is so the parting surface if the seal is not at the mating surface of the cap and block. It is less likely to leak that way. A rear main seal leak is a real pain to deal with aftet the engine is installed. You have the best opportunity to do it right now so if it were me I'd pull the cap and rotate the seal a bit.
Any good sealer should be fine. (RTV is an acronym for Room Temperature Vulcanization) I think using the stuff in the gun will be fine and easier to squirt in.

 

[fastblackracing]

The permatex Ultra line of rtv sealers work better for me in oil type applications. I have used the black, gray, blue and copper in the ultra line with great results. Regular rtv not so much. Like v6 87 said throw the rubber wedges away.

 

[Chuck Leeper]

Also, I put a THIN smear of rtv on the main cap parting face....

 

[v6turbo87]

Yes Chuck that is also called out in the procedure I wrote.

 

[turbodave231]

Send those side seals and nails to me!! I always use them and NEVER have leaks around the rear cap. I fill the groove about 1/4 full of RTV before pushing the side seal in place.

The side seal acts like a syringe and pushes the RTV out every little gap. I also use the Red Permatex anaerobic gasket maker on the cap parting surface. I don't see any advantage to offsetting the seal in the cap/block.

 

[Mastiff]

As usual I'm more confused after a few answers then before... Thanks, guys! I'll just have to discuss this with my mechanic and find out what we'll do. Oh, and I believe Permatex is that brand he was using and considered the best around!

David R, do you use the metal pins as well, or just the rubber part?

 

[whitehot1]

Just to add to what has already been said and follow the procedure given.This is not a hard job to do. I just use a small tube of Permatex clear RTV to fill the side cavities of the cap. The important thing is to keep squeezing and filling until you see the RTV coming out between the parting lines of the cap and block,once you see that you know you got it right. Then i use a wet pipe cleaner and run it down into the RTV to help it get rid of any air pockets and to cure,i just snip it off and leave it in there,no problem. The last one i did was in the car and that was almost 6 years ago,still no leaks. I let the engine sit after i'm done usually a week to let everything get good and dry and setup before i add oil to it. Just plan your job out and give yourself plenty of time. The rewards of not having any oil leaks is well worth it.

 

[GNONYX]

Here are a couple of sites for you to read and the second site is for TTA owners
http://www.gnttype.org/techarea/engine/rearmain.html
http://home.comcast.net/~tta1456/rearmain.htm

 

[v6turbo87]

I am sure turbodave's method is just as good. You will run into a problem if the rubber seals are used with NO sealer. As I said, the factory only used sealer.

 

[turbodave231]

It is a fact that Plant 36 used RTV in production when the engines were built. The GM Service procedures instruct you use the side seals.

Yes, use the pins to expand the seals... I would not use the seals without RTV.


Sent from my iPhone using Tapatalk

 

[markrussell0927]

I use rtv and the wedges, never had any leaks.

 

[mikestertwo]

I use rtv and the wedges, never had any leaks.

X3....I have built a lot of Oldsmobile motors in my day and never have had a leak using both RTV and the wedges with the nails. A thin film of RTV between the cap and the block near the seal is also a good idea. JMHO

 

[Mastiff]

Thanks, guys!

 

[GNTtypeKid]

Have been reading up, researching and prepping to do this myself on my T and have found myself getting stuck on the "1/4 inch rotation of the the seal where it meets the main cap" part. Is there a thread out there I'm missing where this is better explained? Thanks.

 

[RmvBfrFlght]

I'll go it a go, take a look at a main bearing cap and the block were it gets installed. Where the bearing cap meets the block is called the 'parting line.' It is basically straight across the block.

The two halves of the rear main seal has the same thing. Where the two halves meet is the parting line. What is done is to set the seal into the block so that the seal parting line isn't on the same plane as the cap parting line. That is, push one end of the seal further into the block so that it is recessed about 1/4".

Which has the other end of that seal now protruding from the block by a 1/4". Basically it has been rotated.

Now do the same to the seal in the cap, making sure to recess the correct end to line up with the blocks protruding end.

RemoveBeforeFlight

 

[GNTtypeKid]

Rmv, I appreciate the explanation. That about clarifys it.

 

[GNTtypeKid]

Rmv, I appreciate the explanation. That about clarifys it.