# 1966 GTO Main Bearing Seal Leak Question



## take5 (Aug 9, 2009)

Are there any good products out there for sealing main bearing leaks?
My local performance/speed shop has recommended a product called
"Bearin' Seal" that you add to your oil made by the GUNK Company. Has anyone used this or another product and what kind of results did you experience. I have the original 389 with 120K miles and have a small amount of oil leaking from main bearing. I also discussed this main bearing seal leak with a mechanic and he said repairing by means of overhauling engine would correct the leak for a time, but the same leak would return down the road so to speak. All input is always welcome.


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## Gran Turismo (Jan 12, 2010)

The oil additives on the market only work for a short while in my experience' they work by swelling the seal supposedly.( depends how bad leak is ). The long term way would be take out main seal and replace with new. Front or rear??


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## 05GTO (Oct 6, 2004)

I've had good luck with the Viton Seal from BOP Engineering,

BOP Engineering Engine Accessories


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## goat670 (Aug 10, 2008)

*rear main*



take5 said:


> Are there any good products out there for sealing main bearing leaks?
> My local performance/speed shop has recommended a product called
> "Bearin' Seal" that you add to your oil made by the GUNK Company. Has anyone used this or another product and what kind of results did you experience. I have the original 389 with 120K miles and have a small amount of oil leaking from main bearing. I also discussed this main bearing seal leak with a mechanic and he said repairing by means of overhauling engine would correct the leak for a time, but the same leak would return down the road so to speak. All input is always welcome.




the vitron seal is what I put in mine,, but have not driven it yet,supposed to be the best around


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## 66tempestGT (Nov 28, 2009)

you can replace the two piece seal without removing the crankshaft. if you can get the engine up high enough to remove the oil pan (take out the mounting bolts) you can do this in the car.


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## Too Many Projects (Nov 15, 2008)

You don't need to "overhaul" the whole engine to repair a leak although with 120k it may benefit from it.
As 66tempestGT says, just replace the seal. You may need to remove the engine to do it but a competent repair facility should know how and be able to perform the repair in the car.
I'm guessing the mechanic you talked to about replacing the seal isn't aware of the Viton seal as an upgrade from the original rope one. Check with other repair shops in your area if you aren't able to do this repair yourself.


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## take5 (Aug 9, 2009)

Thanks guy's I'll check with my local mechanic. My guess is that he is probably not aware of the vitron seal that is available and specifically engineered for the Pontiac engine.


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## GTO JUDGE (May 14, 2005)

For my rear main seal leak I have been using BarsLeak Rear Main sealer additive
When I purchased the car it was leaking pretty good. The Bars Leak has helped. I drove the car pretty good last season and only added a couple of quarts all season. I also added their version of that for the transmission too. My leaking problems are not like they were when I purchased the car. During the cold season though the leaking increased I am suspecting the seals have shrunk up a bit. I just changed the engine oil last week and added 16 oz of bars leak again. I am prolonging the change out of the rear main seal. Best quote I got was 400 highest was 800. I will fix this once the leak gets worse. Is there any other additives better than BarsLeak?


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## geeteeohguy (Feb 2, 2008)

Stop leak formulas for oil seals work by softening up and expanding the rubber seals. Sort of like when you get oil on a rubber bike tube or glove. It swells, but degrades slightly. I don't for the life of me see how the additive could swell up an asbestos impregnated rope seal. The only "fix" is to remove the engine to replace the entire seal. I bought a Vitron BOP seal, and will be installing it soon. I have installed 2 others in the past 2 years, and they do not leak (yet, anyway). I hav e read that the asbestos was removed from the rope-type seals in the mid '80's for our safety , and all I know is that my rope sealed 389 built in '81 with the asbestos seal is leak free still, and my 400 built in '88 with an "improved, safer" rope seal has leaked almost since day one. GM has a tool and a service proceedure for in-car replacement, and it is a duesy. You need to jack the motor, support the front timing cover with a special tool, pull the rear cap, and you end up pounding 3/8" long pieces of rope into the existing seal and using new rope on the bottom half. It works about 70% of the time. Me, I've BTDT. I k now it'll be easier in the long run to yank the motor, put it on a stand, and do it right. That way, the engine can be repainted, the engine bay can be cleaned, etc. Good luck! (man, that Bars leaks stuff sounds tempting, though!!!)


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## GTO JUDGE (May 14, 2005)

geeteeohguy said:


> Stop leak formulas for oil seals work by softening up and expanding the rubber seals. Sort of like when you get oil on a rubber bike tube or glove. It swells, but degrades slightly. I don't for the life of me see how the additive could swell up an asbestos impregnated rope seal. The only "fix" is to remove the engine to replace the entire seal. I bought a Vitron BOP seal, and will be installing it soon. I have installed 2 others in the past 2 years, and they do not leak (yet, anyway). I hav e read that the asbestos was removed from the rope-type seals in the mid '80's for our safety , and all I know is that my rope sealed 389 built in '81 with the asbestos seal is leak free still, and my 400 built in '88 with an "improved, safer" rope seal has leaked almost since day one. GM has a tool and a service proceedure for in-car replacement, and it is a duesy. You need to jack the motor, support the front timing cover with a special tool, pull the rear cap, and you end up pounding 3/8" long pieces of rope into the existing seal and using new rope on the bottom half. It works about 70% of the time. Me, I've BTDT. I k now it'll be easier in the long run to yank the motor, put it on a stand, and do it right. That way, the engine can be repainted, the engine bay can be cleaned, etc. Good luck! (man, that Bars leaks stuff sounds tempting, though!!!)



The barsleak is buying me some time. I had my local garage guy tell me 800.00 to replace the seal but suggested I wait until the leak gets pretty bad, bad to the point I am really using oil. Last season 2 qts wasn't that awful bad had I not been using that I'd be using more. 

Had another place quote me 400 just by jacking the motor they claim they replaced many GTO seals with the very one suggested here. I will verify that with them... I'd want to be there so I can degrease the back of the motor and paint. At any rate..... The Bars Leak works... but if a poncho motor isn't leaking oil it aint a GTO.


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## 68greengoat (Sep 15, 2005)

GTO JUDGE said:


> The Bars Leak works... but if a poncho motor isn't leaking oil it aint a GTO.


Well mine must be a true GTO fer sure! This Bars Leak. can it be purchased at my local autoparts store? Any ones in particular? I'm all for buying time....


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## GTO JUDGE (May 14, 2005)

68greengoat said:


> Well mine must be a true GTO fer sure! This Bars Leak. can it be purchased at my local autoparts store? Any ones in particular? I'm all for buying time....


Here Advanced Auto, and AutoZone has it... Sometimes there is a 2.00 rebate on the bottle. 

Bar's Products, Inc. - Premium Automotive Chemicals

Bar's Leaks Rear Main Seal


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## 68greengoat (Sep 15, 2005)

Very cool, thanks for the links....


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## GTO JUDGE (May 14, 2005)

I use it in my trans and radiator. (on the '70)


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## Eric Animal (Oct 28, 2007)

If it only leaks "a little" and has 120,000 miles on it, I would leave it alone until rebuild time.....In my opinion, you are opening up a can of worms. :cheers Eric


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## Rukee (Feb 8, 2007)

A thicker weight oil and some oil stabilizer like LUCAS may help slow it down as well.


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## GTO JUDGE (May 14, 2005)

Yep I agree Eric.... Its not that bad cardboard is easily replaced. :lol:

I'm runnin 20w50 Valvoline Racing oil with high zinc its pretty thick.

I remember my first car... 66 corvair..... quart a week and if I bought stock in STP I'da been rich.


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## Too Many Projects (Nov 15, 2008)

GTO JUDGE said:


> I remember my first car... 66 corvair..... quart a week and if I bought stock in STP I'da been rich.


'54 Chev with a stovebolt 6. Remember seeing the old cars with a blue smoke screen following them down the road ? that was mine....:willy: Straight 30 weight bulk oil and 2-3 cans of STP. What leaked on the dirt driveway just helped keep the dust down...:lol: It still spun a bearing a few months after purchase.


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## Chris Holabaugh (Jan 18, 2009)

*Main Bearing Seal.*

If you decide to put in a non rope seal, make sure nothing is attached with the seal. I pulled the engine in my current rebuild because it was leaking very bad. When the engine builder put in the non rope seal they had permatex on the seal and that is what caused it to leak, and I mean leak.


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