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Old 05-26-2015, 12:31 AM   #1
norcalal
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Default sudden rear main leak

Drove my 30 coupe on a 2200 mile tour, virtually no oil consumption, as usual. Let her sit for 6 months, changed the oil, suddenly she has more blow by than usual, and oil is pouring out form the flywheel housing. What happened?
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Old 05-26-2015, 01:22 AM   #2
Mike V. Florida
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Default Re: sudden rear main leak

Added too much oil?
The rear cap drain tube fell out?
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Old 05-26-2015, 05:11 AM   #3
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Default Re: sudden rear main leak

Push your dip stick all the way in and check the oil level. Bet you got hung up on the tang and overfilled her.
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Old 05-26-2015, 05:43 AM   #4
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Default Re: sudden rear main leak

Stuck ring(s). Drive it
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Old 05-26-2015, 10:29 AM   #5
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Default Re: sudden rear main leak

The 'cup is half-empty' response: Detonation broke a ring and/or ring land and blow-by is pushing oil out the rear main.
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Old 05-26-2015, 11:08 AM   #6
BILL WILLIAMSON
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Default Re: sudden rear main leak

I once slapped Minervas' oil cap down too tight & shut off the vent holes, she leaked like a SIEVE!
Bill W.
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Old 05-26-2015, 05:35 PM   #7
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Default Re: sudden rear main leak

It could be a number of things. If it's truly coming out of the flywheel housing hole it really has to be coming out of the rear main cap or the camshaft rear area. May sure you don't have any restriction in the breather that would build up pressure in the engine that would cause it to blow out the rear main. You can check for wet plugs by pulling and checking for oil fowling.... that's an easy one.

If all is well then I would pull the pan, check the oil tube is clear... it could have gotten plugged or fallen out.... It's kind of remote but the welch plug in the back of the rear main cap could have fallen out or leaking... which is a direct path of oil to the flywheel housing. Also a broken rear main thrust can also cause excessive leakage as well. As Mike said too much oil can also cause excessive leakage.. but I'm assuming you have a correct level.

Pulling a pan and checking out is a couple of hour job... Please keep us posted.
Many thanks,
Larry Shepard
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Old 05-29-2015, 12:41 AM   #8
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Default Re: sudden rear main leak

I put on a different breather extension (road draft tube) drove her hard about 75 miles, not hardly a drop out of the rear main. Happy as ever. Thank you for the input, guys!!
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Old 05-29-2015, 05:16 AM   #9
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Default Re: sudden rear main leak

Did you by chance park the car with the nose pointed uphill before the leak appeared?
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Old 05-29-2015, 09:29 AM   #10
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Default Re: sudden rear main leak

rear main or rear cam gasket ?
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Old 05-29-2015, 11:18 AM   #11
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Default Re: sudden rear main leak

This might help also
http://www.antiqueenginerebuilding.c...RMAINLEAK.html
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Old 05-29-2015, 03:05 PM   #12
Barry B./ Ma.
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Default Re: sudden rear main leak

Quote:
Originally Posted by BILL WILLIAMSON View Post
I once slapped Minervas' oil cap down too tight & shut off the vent holes, she leaked like a SIEVE!
Bill W.
Hi Bill, I bought a new cap but it didn't have the tabs bent so when I put it on it blocked the air flow and just like your experience the oil started blowing out the rear main area in about 10 miles. It actually created a path through the paper gasket near the rear of the cam.
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Old 05-29-2015, 03:42 PM   #13
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Default Re: sudden rear main leak

There was a guy who had a brand new $4500 rebuilt engine destroyed by a plugged up breather.

He changed the oil and replaced the breather cap with one that was plugged up.

The breather cap, taken from his old engine and installed on his new engine maybe, had a clogged up "Brillo pad" in the breather cap.

The back pressure built up and pumped all the oil out the rear main.

Engine went 70 miles on a tour and seized up.

I never heard if it was a Babbitt or insert engine or how much the repair was.

Last edited by Benson; 05-29-2015 at 04:02 PM.
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Old 05-29-2015, 03:52 PM   #14
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Default Re: sudden rear main leak

I have one of these on my engine. Works great, lets it breath and doesn't make a mess in the engine compartment.
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Old 05-29-2015, 11:22 PM   #15
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Default Re: sudden rear main leak

That is what I replace the previous vent tube with. did the job. thank you!
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