Rear main "seal"

RudyOnWheels

RudyOnWheels

Member
I know these cars dont have a rear main "seal" persay, but a Rope seal. mine doesnt seem to leak much when it sits, but man watch out when you run it. It is like that oil leak in the gulf. I was told that they were designed to leak a bit on the felt "pad" above the wishbone mount, but mine is beyond that. This is an unrestored car. How bad of a job is it to pull the engine on one of these to do the job? It's in my coupe. Should I take care of this or just feed it oil til it pops? An old timer from my model a club said it's probably on it's way out the way it is leaking. I know they can be machined for a "new style" modern main seal, but what about just replacing the original?


Thank you,

James
 
Hi Rudy,
If you have a plugged oil tube or oil tube cap it will force oil out the rear main. I made the mistake of trying to install a screen in my oil pan cap a few years ago and a dripper turned into a gusher.
 
I had the same promblem years ago, turn out the oil filler cap internal tabs where missing so when you put oil cap on it would seal up tight and presureize the system. Make sure your cap has the seat tabs?
 
you will get alot of different suggestions from these guys that can be causing the leak. ill throw one at you i had the rear camshaft gasket between the flywheel / clutch housing and engine block pour oil.
 
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Hey Rudy, pull the oil pan off 1st. There is no rope seal for the rear main bearing only the front. See if the drain tube from the rear main bearing is still there. Pull the rear main cap to look for a cracked bearing. If its cracked put it back together as best you can and buy oil by the case or plan to pull the engine and have the engine rebuilt. Good Luck
 
When I got my car it had a bad leak as you describe, it turned out to be caused by a clogged oil return passage in the rear bearing block. I drilled it out and it has been fine since. The bearing block can be removed from under the car without having to pull the engine.
 
I’ll give you another twist. My fresh rebuilt engine would hemorrhage oil when I drove it, also a little oil blowing out the oil filler tube. My first guess was the rear seal, but why the oil blowing out the filler tube ????

I checked the dip stick and the oil level was right on the full mark. Actually, it was touching the bottom of the “F.” The dipstick measured the correct length so I thought I was good. However, before I tore into the new engine, I removed about a half to ¾ of a quart of oil, and guess what? My oil hemorrhaging stopped!!! Yes, I still have a small oil spot when I park but nothing like before.

What I’m recommending is if your dip stick shows that, you are “Plum Full” then first drain some oil out of the oil pan and see if that mitigates the problem of at least makes it tolerable.


Let us all know what you find.
 
A properly rebuilt engine will not leak oil more than a few drops adn a modelrn seal is not necessary. First try lowering the level as suggested. My new rebuilt was fine on level roads but leaked after going up some steep slopes. Started to panic but lowered the level a little and no problem.
 
Downeaster said:
Hey Rudy, pull the oil pan off 1st. There is no rope seal for the rear main bearing only the front. See if the drain tube from the rear main bearing is still there. Pull the rear main cap to look for a cracked bearing. If its cracked put it back together as best you can and buy oil by the case or plan to pull the engine and have the engine rebuilt. Good Luck
Click to expand...

Worn out rear bearing is what I found with mine that leaked. See how much the crankshaft can move from front to back. If alot, that is also showing that the rear main has seen better days.

Idling around town was no problem but when I took it out for a drive it would pump out the oil. Kinda like the Gulf of Mexico.

Neal
 
It barely drips or doesnt leak at all when it is just siiting, but when it gets driven and warms up, there she goes!!! Almost a steady stream.... I will inspect the oil cap in the morning, and take a spin with her off to see what happens. What about drilling a small relief hole in it while I wait for a new one.... I have replaced the valve cover gaskets, and the oil return pipe gaskets. All that is left is the pan gasket and the main seal, other than these possible anomalies you guys suggested...

I will report back!!

Thank You, James
 
Tried a spin with the oil cap open, still leaks like it is the end of the world, have considered hanging an "I.V. bag" on the car with oil in it......

Thanks, James
 
This is a long shot as I don't know the car's history, but Bratton's site mentions that if the oil return tube for the rear main is screwed in too far it could be blocking the opening and forcing the oil into the flywheel housing. It could be checked by dropping the oil pan. I noticed mine was brazed in place when I had my pan off a few weeks ago.
 

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Thanks for the leads fellas, looks like the pan is coming off next week, we shall see what is going on.... Looking at the gunk that once was oil that I drained out of it when I changed the oil, I would guess that the oil tube/galleys in the rear main are plugged... It barely drips when Just sitting cold, but once it warms up it starts flowing like a river.....

James
 
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