Pan gasket / rear main seal leak question (big block mark IV)

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GRTfast
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Pan gasket / rear main seal leak question (big block mark IV)

Post by GRTfast » Fri Sep 14, 2018 1:44 pm

Hello all,

I have a tiny oil leak that has developed at the rear of my engine (one small drop on the garage floor after driving). I have traced it to the rear oil pan "hoop" just below the crank, using baby powder. I don't think it is the rear seal because there is no oil on the crank or the flywheel, but I was thinking that it could be possible for oil to leak around the outside of the (2 piece) rear main seal, and drip down the back of the pan without wetting the crank or flywheel. Does that sound reasonable, or is it usually the case that a rear main seal leak will oil down the flywheel? The existing oil pan gasket is a one piece Fel-pro.

I have a new oil pan gasket, but I am wondering if I should go ahead and do a rear main seal while I have the pan off. I'm a little apprehensive about attempting the rear seal under the car with the crank in place. I know it can be done, but it looks like it could be a pain.

Thoughts?

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Re: Pan gasket / rear main seal leak question (big block mark IV)

Post by rp930 » Fri Sep 14, 2018 2:29 pm

I don’t think I’d do one without the other. Too much labor. It might depend on who and when the rear man was replaced before.

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Re: Pan gasket / rear main seal leak question (big block mark IV)

Post by prairiehotrodder » Fri Sep 14, 2018 2:55 pm

i usually put a few dots of flange sealant under the back edge of the main cap as well.
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Re: Pan gasket / rear main seal leak question (big block mark IV)

Post by DCal » Fri Sep 14, 2018 2:59 pm

My BB Camaro valvecovers off, stock oil pan, distributor out, headers unbolted, motor mounts undone and I still didn't get it 100 percent. Get some buddies and you could do it right easily in a day.

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Re: Pan gasket / rear main seal leak question (big block mark IV)

Post by BillK » Fri Sep 14, 2018 3:46 pm

Before you do anything put some Ultraviolet Die in the oil and drive the car enough so that the die can make it to the leak area. Then get under there with a UV light and you should be able to see exactly where the oil is coming from. You would be amazed at how far it will travel to get to that bottom lip :) I have seen them leaking from the distributor and end up down there even though the top was "dry"
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Re: Pan gasket / rear main seal leak question (big block mark IV)

Post by GRTfast » Fri Sep 14, 2018 4:30 pm

BillK wrote:
Fri Sep 14, 2018 3:46 pm
Before you do anything put some Ultraviolet Die in the oil and drive the car enough so that the die can make it to the leak area. Then get under there with a UV light and you should be able to see exactly where the oil is coming from. You would be amazed at how far it will travel to get to that bottom lip :) I have seen them leaking from the distributor and end up down there even though the top was "dry"
I've verified (baby powder method) that I'm not leaking from the distributor, heads, valve covers, cam cap, or oil plugs in the back of the block. It's either the rear main or the oil pan, and I'm leaning towards pan because the flywheel doesn't have any oil on it. We shall see....

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Re: Pan gasket / rear main seal leak question (big block mark IV)

Post by pamotorman » Fri Sep 14, 2018 5:23 pm

I have used this for pan leaks and it works. https://www.permatex.com/products/adhes ... ak-repair/

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Re: Pan gasket / rear main seal leak question (big block mark IV)

Post by GRTfast » Mon Sep 17, 2018 12:44 pm

Seems I have fixed it. The pan is a stock stamped steel style pan. I made a wooden piece that fits up to the rear pan hoop, and gave it 3-4 good whacks with a dead blow hammer. My intention was to compress the gasket a little bit more in the area of the leak. I've taken two decently long drives now with no leak. :)

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Re: Pan gasket / rear main seal leak question (big block mark IV)

Post by Speedbump » Mon Sep 17, 2018 4:17 pm

And there ya' have it. Real world proof that "if you can't fix it with a hammer, it's an electrical problem." :D
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Re: Pan gasket / rear main seal leak question (big block mark IV)

Post by GRTfast » Mon Sep 17, 2018 4:57 pm

Speedbump wrote:
Mon Sep 17, 2018 4:17 pm
And there ya' have it. Real world proof that "if you can't fix it with a hammer, it's an electrical problem." :D
:lol:

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