87 GN rear main engine seal

[Donutblue]

The rear main engine seal on my GN is leaking, the prior owner said he put a new rear main engine seal in before I purchased it and he said he filled it with silicone. I'm going to re-do it, any suggestions ? What do most use, Rope or rubber seals ? --- No, I'm not using synthetic oil.

 

[Dabigguy]

Do a search on rear main seals. You will find some very informative articles and some with step by step pics.

 

[83ttypecooled]

leaks

Hi,
These cars leak with regularity.Your best bet is to try, once again, to seal the crank with a neoprene seal. The pan gasket is the real problem,though.

 

[turbofabricator]

Use a cork pan gasket with a light coat of silicone on both sides while you are at it. Most vendors on here carry them.
Use a Fel-Pro neoprene rear main seal, and ditch the rubber side seals. Use a good caulking gun with a cartridge of Ultra-Black and after you smear a light coat of silicone on the parting line (rear half only) of the main cap, torque it to 100 ft.lbs and then pump the Ultra-Black into the side seal cavities. You will be able to see the sealant squeeze-out of the front and back of the block. Take a small stick/spoon and smear it flush on the inside of the block. You MUST have ALL the oil residue off of both the block and main cap for this to work. Use brake-clean to get everything real clean. Use a light film of oil on the seal itself.

 

[83ttypecooled]

Hi,
It will still leak. Then what?

 

[750H.P.V6]

Ken,

I've always used the side seals with the pins they come with and had very good results. I tried the silicone trick for sealing the rear main cap and didn't have much luck. I've used both cork and rubber pan gaskets too and had good results with both. I agree with you that all the surfaces must be spotless and oil free prior to installation.

Neal

Use a cork pan gasket with a light coat of silicone on both sides while you are at it. Most vendors on here carry them.
Use a Fel-Pro neoprene rear main seal, and ditch the rubber side seals. Use a good caulking gun with a cartridge of Ultra-Black and after you smear a light coat of silicone on the parting line (rear half only) of the main cap, torque it to 100 ft.lbs and then pump the Ultra-Black into the side seal cavities. You will be able to see the sealant squeeze-out of the front and back of the block. Take a small stick/spoon and smear it flush on the inside of the block. You MUST have ALL the oil residue off of both the block and main cap for this to work. Use brake-clean to get everything real clean. Use a light film of oil on the seal itself.

 

[Lee Thompson]

I agree with Neal

Ken,

I've always used the side seals with the pins they come with and had very good results. I tried the silicone trick for sealing the rear main cap and didn't have much luck. I've used both cork and rubber pan gaskets too and had good results with both. I agree with you that all the surfaces must be spotless and oil free prior to installation.

Neal

The coat on the mating surface should or MUST be paper thin. I have installed more than 1 this way (using Loctite 518 on the mating surface) and have yet to have any of them leak. The only time I had a rear main to leak was on an after market crank which had no knurling.

 

[Lee Thompson]

Mine don't leak

Hi,
It will still leak. Then what?

That's what seals and gaskets are for.

 

[turbows6]

I used the side seals and nails with a thin coat of grey silicone also, and it's absolutely leak free. Key is to make sure everything is clean. I also don't line the mating surface of the 2 piece seal up with the cap I offset the rear seal slightly.

 

[BlackBandit]

I've done a few with the neoprene seals and used the thinnest layer of silicon possible on the cap mating surfaces and pumped the sides full of silicone and never had one leak. I've always wanted to try the side seals but I can't bring myself to try it because I KNOW the other way works. I'd be in the opposite situation if I'd tried the side seals first. I'll add the emphasis that everything has to be absolutely clean and dry. (except the seal lip) That's the key to sealing anything whether you use rubber or cork. FWIW I don't have a problem getting the rubber pan gaskets to seal.

 

[750H.P.V6]

Lee,

I think what I wrote didn't read as well as I would have liked. What I was trying to say is that I don't subscribe to the idea of discarding the side seals completely. Like you said there is still a need for a very thin coat of sealant between the bottom of the main cap and the block itself. I use silicone for that.

Neal

The coat on the mating surface should or MUST be paper thin. I have installed more than 1 this way (using Loctite 518 on the mating surface) and have yet to have any of them leak. The only time I had a rear main to leak was on an after market crank which had no knurling.