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Rear Main Seal Leak
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samstrader
Posted 2020-05-04 2:02 AM (#597738)
Subject: Rear Main Seal Leak


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Posts: 196
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Location: Beaumont TX
When my engine (1955 259 V8 Poly) was first rebuilt in 2011, a rubber rear main seal was installed. This car originally came with a packing seal. It ran OK for a couple of hundred miles and then started leaking. Like 5 or 6 drops every time I park it. I drove it about 500 miles and the rear main bearing wiped out.

When I rebuilt it again this year (just main bearings and a new seal), I used a rubber seal again. It's the Fel Pro seal that Hot Heads said everyone uses. It's leaking again.

I'm trying to figure out what I did wrong. The crank has those shallow diagonal cuts in the steal area that I think were to help push oil away from the packing. I still have those cuts on the crank even though I'm using a rubber seal. I asked my machinist if a rubber seal would work with those cuts still in the crank and he said they would not be a problem

But something is wrong because the seal is leaking. I was very careful to put it in correctly (at least I think so). I'm sure the big lip is right. It is pointed to the interior of the engine. And the main bearing cap crushed down evenly and completely. I checked this.

Should I use a rubber seal or should I go back to the packing. My mechanic and Hot Heads said the rubber seal is way better but it seems to me like the packing would be a lot more forgiving.

Anyway. Sorry for all of the questions. Just looking for some guidance on how to do this right because I may fix this when I fix the cam bearing problem.

Thanks,

Sam
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Powerflite
Posted 2020-05-04 12:45 PM (#597756 - in reply to #597738)
Subject: Re: Rear Main Seal Leak



Expert 5K+

Posts: 6571
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Location: So. California
Carefully inspect the seal when you take it apart to discover where the problem was. The packing works well at the beginning, but doesn't last as long as the rubber, in general.
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samstrader
Posted 2020-05-05 4:26 AM (#597808 - in reply to #597738)
Subject: Re: Rear Main Seal Leak


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Posts: 196
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Location: Beaumont TX
Thanks Powerflite. Do you think the groves on the crank in the seal area would make the seal leak. It seems to me like those groves (which I think would be there for the packing) would make a rubber seal leak. If a rubber seal works, I think I can change that out without pulling the crank shaft. That's a big positive for the rubber seals.

thanks,

Sam
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GaryS
Posted 2020-05-05 7:01 AM (#597811 - in reply to #597738)
Subject: Re: Rear Main Seal Leak



Elite Veteran

Posts: 1100
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Location: Ponder, TX
In 1964 I worked at a Chrysler-Plymouth dealer. We received a notice from the factory that several marine 318 crankshafts had been inadvertently installed in passenger car engines. Apparently, the knurling is ground differently on counter rotating engines, and the result was oil leaks that couldn't be fixed with new seals.

Not even suggesting that it's possible on yours, just saying that strange things happen and sometimes those little things mean a lot.
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samstrader
Posted 2020-05-05 12:13 PM (#597818 - in reply to #597738)
Subject: Re: Rear Main Seal Leak


Veteran

Posts: 196
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Location: Beaumont TX
Thanks GaryS. If I remove the main, I know how to check what you are mentioning and I did not check this before. So it is a good thought. It just seems to me that you would not want any knurling if you have a rubber seal. Do you think this is right or am I just thinking wrong?
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samstrader
Posted 2020-05-05 12:14 PM (#597819 - in reply to #597738)
Subject: Re: Rear Main Seal Leak


Veteran

Posts: 196
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Location: Beaumont TX
I forgot to say that it is definitely the little things that mean a lot. I've looked over so many little things working on my car. That's what experience is so valuable for. The experienced experts know the little things to watch out for.
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