# Rear Main Seal still leaking



## timmyg (Jan 2, 2012)

Hello to everyone. It has been quite a while since I have been on the Forum. Soon I will be removing my Engine for the third time since I got my 65 GTO back together after restoring it. Some of you have given me great advice and information I needed while I was restoring the car. My car turned out great and I am very happy with it. What is still haunting me is the Rear Main Seal. When I bought the car, the 70 455 HO that was in the car had very minimal miles on it since it was rebuilt but did have a lot of time on it as the car had been garaged for a long time. Anyway the previous owner told me that the Rear Main Seal leaked pretty bad and I should replace it. Since I was restoring the car anyway I had already decided that the Engine was coming out and I would re gasket and reseal everything since it had been sitting for quite some time. Long story short I replaced the Rear Main Seal with the Rope Style that came with Felpro Gasket Kit. It leaked terrible. Took engine back out and asked questions on the Forum. Most folks recommended the BOP Viton Seal. Purchased the BOP seal and installed it to the letter by instructions. Put Engine back in and the seal leaked worse than the Rope Seal. Took Engine back out, asked more questions and the Graph Tite Seal from Best Gasket Co. was recommended. Purchased the Graph Tite Seal and installed exactly per instructions. Put Engine back in and it started leaking after only a few minutes. It leaks enough where I leave a trail of oil drops coming from the vent hole in the Converter Cover and the Rear Bumper gets an oil film on it whenever I drive the car. Has anything changed with technology of lately or does anyone have any other advice for me on how to get this corrected. I was going to get a machinist to thoroughly examine the Crank and Rear Main Cap this time prior to seal number four. Could it be the fourth time is a charm??
Any advice appreciated
Timmy G.


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## rt66gto (Feb 14, 2013)

Timmy G., I am sorry I don't have any advice (nor enough knowledge or experience to offer any) but, 

I intend to watch this thread clsoely as my wife's '66 GTO is leaking pretty badly from the main seal also and it is the original (never removed or anything) engine. With just 30,000 miles on it . . .

The only thing that eclipses my heart aching as I read your saga is my confidence the members of this forum will help you with what you need!


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## GTO JUDGE (May 14, 2005)

Stupid questions here but .....

Did you carefully examine the metal areas for dings in the areas, protrusions, or any other issue that may cause the seals not to properly seat? Are the mating areas ok not warped? Did you use the right sealing compounds and let it sit for 24 hours or so before finishing up the job? When reassembling did you somehow unknowingly disturb the gasket?


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## BearGFR (Aug 25, 2008)

Give Jim at Central Virginia Machine a call. Something's not right for you to have had this many problems with all the different seals.

Bear


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## skurfan (Sep 19, 2012)

Mine sat for thirty years after the rebuild. When I got it, and did the usual fixes to get it drive able, it leaked. Pulled the pan, then the motor and found that the crank had a bit of corrosion at the seals where it sat for years. I guess moisture finds a way to get in there. Took the crank and polished it and back together. So far so good. If your crank has ANY spots on it, it will corrode and work on your seal and you will have leaks.


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## rwarnerjr (Sep 27, 2012)

Here is something that might work for you. What it does is it makes hard seals soft again and that is usually what causes seals to leak. A friend of mine used it on a leaking manual transmission he had and it worked. I know your seal is not old but I would try it. Good Luck


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## geeteeohguy (Feb 2, 2008)

What Bear says. Something is not right. The big journal engines like yours are more likely to have rear main issues due to alignment and casting issues at the rear main cap. Also, if the engine has been align honed or bored, that can cause out-of-true problems. The Best Gasket Graphtite seal is the most recommended for your application. If this type of seal is installed too tightly, the crank will grab it and burn it up, however. Some cranks need to be polished where the crosshatch section is to avoid tearing up seals. I've installed all but the Graph-tite and have had 100% success (4 engines so far) but these were small journal engines, and the rope seal I used in my 389 over 30 years ago (and still leak free) was an old style asbestos seal which has been out of production since the mid '80's. The 3 BOP Viton seals have been leak free on two 400's and another 389 for thousands of miles and several years now. I feel for you...this is not a fun job, especially on a restored car. Have the crank checked out, and if you can, the alignment of the mains.


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## rwarnerjr (Sep 27, 2012)

Have any of you guys tried this stuff AT 205? It is supposed to soften of leaking seals.


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## Glenn's Goat (Sep 7, 2010)

I think you need to pull the crank examine it of course , and set the seal in the journal the way it was meant to be. The problem your probably having is when your pulling the seal thru the upper journal, your stretching in out by the time it goes thru it's to thin to seal the upper part of the crank. You can pull seals thru small block and big block Chevys all day long. But not a pontiac.


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## timmyg (Jan 2, 2012)

*Crank was pulled each time*

I have pulled the Crank each time and installed the seal with crank out. I have never put the seals in with the crank still in the car.


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## 646904GTO (Feb 10, 2008)

post a picture of the main cap with the seal and the block with the seal in it. Lets see what your looking at.


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## JeffW (Aug 30, 2009)

I feel for you! I also had problems when I replaced the internals of my Pontiac. Ended up pulling it two additional times. Finely gave up gave up on viton seals when I actually looked at the crank. Those serations where the rope seal meets are ment to lube the rope seal. They hold oil and lube the rope seal. (Just like a industrial pump with packing and packing glands.) On my third attempt I also used the graph tite seal. Followed the instructions with one minor change. I installed 4 roll pins, 2 in the top (cap) and 2 in the bottom(Block section) to help keep the packing in place until proper break in was acheived. I also lubed the poop out of it when installing. 2 years now and not a drop. I will go on record and say viton seals do not belong in a Pontiac unless you have the serations machined off. In any case... I wish you good luck. It's not an easy job by any means.


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## rexs73gto (Nov 25, 2012)

timmyg, are you sure it's the crank seal & not the oil pan seal??? There are 2 type of rear pan seals, one with 3 tabs & one with 5 tabs. If your using the 3 tab seal on an engine that should have a 5 tab seal it will leak every time. The 3 tab seal will push out under the pressure of the internal engine pressure & look like a rear main seal leak. Also when you used the viton seal did you make sure you made sure the lip was facing the right way??? If you pan is leaking because it has a 3 tab seal you will have to modify the pan to except the 5 tab seal. I went through that problem in a 455 in my 73 T/A. I had to modify the pan to use the 5 tab seal because the pan was made for the 3 tab seal & would blow out the seal every time I put it in. The only engines that used the 3 tab seal are the engines that have the groove in the main cap for them. Thats what holds the seal in place . If you don't have a groove in the main cap for the 3 tab seal it will leaks,,,, for sure.


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## rexs73gto (Nov 25, 2012)

If you need any more on this you can write me at [email protected] & I can help you out on this & you will have a leak free engine. Thanks Rex.


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