Oil leak on rear of engine

[classic car repair]

I have a 1938 Ford Pickup 1/2 ton, flat head v8. When it in the shop running, no oil leak, If you run down the road about 2 miles and back, put in the shop, there is a large oil leak on the floor, coming out of the bell housing, can it be a rear main seal or a gasket on the back of the engine? It only leak bad after a road test, not running in the Shop? Thank You

[Jack E/NJ]

>>>there is a large oil leak on the floor,>>>


How large? There's a labyrinth seal, not rope or rubber. Probably overfilled and some blowby. Try using 4 or 4.5 quarts, not 5.

[alanwoodieman]

too much oil, what weight oil? 20W50 is best

[classic car repair]

I used 20W50 oil, still leaking, The oil is at the full mark, I think the rear main is dry up from sitting for 25 years, Thank's

[joe 1950]

Dont always go by the dip stick how much oil did you put in it i agree with woodyman good friend of mine had a similar problem with his 35 v8 p up then he drained and only put in 4.5 quarts problem solved also he has no oil filter

[Jack E/NJ]

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>>>I think the rear main is dry up from sitting for 25 years,>>>


No. It's a pot metal labyrinth seal. Nothing to dry out. Suppose it could break though.
https://reds-vintage-parts.com/red-s...ls-janfeb-2003

[flatjack9]

Make sure your breather cap is not clogged up. That can pressurize the engine and blow oil out.

[Ken/Alabama]

You sure it’s engine oil and not transmission oil?

[classic car repair]

It only took 4 qt of oil, it has no oil filter, oil coming out of the bell housing by the cotter pin, it only leak when I road test, when in the shop running, no leak, it a big oil leak?

[Fritz]

How large of a spot is it leaving on the ground? A little spot a couple inches or less in diameter or a puddle? That cotter pin is there because Ford expected it to leak a little.

If it’s sat for 25 years, I’ve heard of the cork oil pan gasket under the rear main drying out. That could contribute to a leak.

[cadillac512]

Make sure the crankcase vents are open as well...the one down at the front right side of the oil pan and also at the fuel pump stand.



Terry

[Jack E/NJ]

>>> I’ve heard of the cork oil pan gasket under the rear main drying out. That could contribute to a leak.>>>


Agreed.This cork strip can also easily get misaligned or twisted out of place upon assembly. Then leak badly even brand new. Glued a neoprene strip to mine before assembly instead of the cork composite. VanPelt panphoto shows where strip is placed.


https://www.fordbarn.com/forum/showthread.php?t=168956

[Brian]

I have in the past experienced that pot metal insert being broken/crumbled, which resulted in big oil leak.

[classic car repair]

Thank You for all the reply