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Old 03-17-2006, 05:59 PM
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SBC Rear Main Seal:

Dale here,

I've had an oil leak coming from the back of my engine. I really can't tell if it's coming from the pan or the rear main seal. The engine is in the car, the tranny is out, flex plate off, pan off and rear main seal out. When I took the rear main cap off, the seal stayed with the crank. I could turn it 360 degrees quite easily. Here's the question. Should the seal have been tight enough in the cap to come with the cap? Should you be able to turn the seal around the crank with ease? Or, should things be a little tighter in there?

I don't want this thing to leak when I put it back together. I will put a new seal and new pan gasket in tomorrow.

I have checked to make sure the oil gallery plugs, cam plug, and freeze plugs on the back of the engine are tight, clean, and not leaking.

Thanks,

Dale

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Old 03-17-2006, 06:31 PM
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Seal should be tight in cap and block. NOT spinning. Also put sealer on back of rear main cap where it bolts to block
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Old 03-17-2006, 07:04 PM
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I'm guessing. When the rear seal was put on, the mechanic put silicon sealer on the ends. When you took it apart the sealer had bonded the half's together so it stayed with the crank. Not knowing how many miles on your motor, the seal could have shrunk causing the leak and looseness.

I had one of those "find me" leaks, it was the oil sender unit leaking.
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Old 03-17-2006, 07:05 PM
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The two piece seal should be snug, but you should be able to rotate it. In fact when you go back with the new one rotate the halves so that the mating line does not line up with the main cap to block surface.

Vince
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Old 03-17-2006, 07:48 PM
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Thanks all.

I plan to put it back together tomorrow, or, at least over this weekend. I'll make sure the parting line doesn't line up. That sounds like sound advice.

The engine only has about a thousand miles on it since the build up but, suffers from leaks on both the engine and the TH400. I believe I found the leaks on the tranny. The engine leak has been harder to find. I did check high first. It's not the engine oil pressure guage line and not the valve covers or intake. The engine is clean and dry down to the pan. Only leaks when running so, I believe it to be under pressure or windage.

Is a dab of RTV on the ends of the seal a good idea?

Dale
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Old 03-17-2006, 10:38 PM
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Not needed on the rear seal but a dab on the pan gasket where the ends meet back there is a good idea.
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Old 03-17-2006, 11:23 PM
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Yes definetly turn the seal so the parting line doesn't line up with the main cap parting line.
Also I like to put RTV on the ends of the seal(were the parting line is)so the line is sealed.
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Old 03-18-2006, 11:30 AM
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I appreciate the input. I have the new seal, new pan (stock), some ARP pan bolts, a used tube of RTV, and I'm off to the shop. Before this weekend is gone I hope to have everything buttoned up, a 3000 stall converter put in, and no leaks.

I'll check back and let you know how it turned out.

Dale
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Old 03-18-2006, 01:21 PM
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Make sure you lube the new seal with vaseline or the like and lube it good, in most practices we would let vaseline stay on it so it would absorb it somewhat, just make sure you don`t install it dry or it`ll be leak city.
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Old 03-20-2006, 02:37 PM
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Just want to report back and let yous guys know the results of my rear main seal thrash.

Doublevision - I got your post before I headed to the shop. Lubed the seal down good then let it alone while I got things ready to reassemble.

Put the new seal in, just the tinyest (sp) dab of RTV on the ends of the seal. Rotated it so it didn't line up with the parting line of the cap and block.

Put the pan on. Lightly glued the felt type rail gasket to the bottom of the block with yellow elephant snot. Little tad of RTV on the rubber end seals to hold them in the groove. Pretty good shot of RTV on the ends of the rear rubber seal. That just looks like a pretty good place for a SBC to leak oil.

Buttoned it all up. Replaced the flexplate, installed a TCI Streetfighter converter, put the tranny back, etc, etc... Then, put it to bed for the night without starting it.

Cleaned up a few details the next day. Busted it off around noon. Drove around town for awhile. Put it back in the barn. NO LEAKS!

I want to thank you all for the advice. I went to some links in the "Knowledge Base" for additional info. This forum makes wrenching just that much more enjoyable.

Thanks again,

Dale
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Old 03-12-2008, 12:19 AM
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Good news, I dont need a new rear main!

I found out that my rear main seal is not leaking and I am happy about that. This s on my chevy suburban with the 383. The leak was coming from the oil cooler adapter. Come to find out , the o-ring on top had complelely rotted out. So, what I did was search for three days to find that ring but without luck. I ended up sealing it with Permatex rtv (grey) . I let the truck run in my driveway for 30 min, and no drips. maybe this is someone elses problem too!
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Old 03-12-2008, 09:19 AM
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Quote:
Originally Posted by 383suburban
I found out that my rear main seal is not leaking and I am happy about that. This s on my chevy suburban with the 383. The leak was coming from the oil cooler adapter. Come to find out , the o-ring on top had complelely rotted out. So, what I did was search for three days to find that ring but without luck. I ended up sealing it with Permatex rtv (grey) . I let the truck run in my driveway for 30 min, and no drips. maybe this is someone elses problem too!
Is it the kind of adapter where the oil filter seals to the adapter itself? If it is I had one of those that was leaking and switched to a late model one where the filter seals against the block. Definitely an upgrade...
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Old 03-12-2008, 02:45 PM
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