leaky rear main,what else is new
 

new to this forum wondering if you guys and gals have any thought on my problem. I have a newly rebuilt stock A engine that leaks from the rear main badly on a cold start. whats weird to me is that upon shutting it off and restarting after a couple minutes it doesn't leak a drop. any thoughts?thanks in advance

Re: leaky rear main,what else is new
 

Re: leaky rear main,what else is new
 

Is the engine under warranty.

Re: leaky rear main,what else is new
 

Like Brent said...warranty or ask for advice from your engine builder?

I don't doubt your observation but the onset of the leak and the stopping goes against the norm I have observed. The only thing I can think of, could there be excessive blow-by past the rings or valve guides causing the crankcase to be pressured. After running, the rings would be lubricated and they may be sealing better. Check that your oil breather cap is not jammed down tight. The stop tabs on the cap could be bent allowing the cap to seat too low. Otherwise...I don't know.
I'm curious, what oil weight are you using? How many minutes of running time are on the engine? Is the leak coming from the cotter pin hole or tracking down the face of the flywheel housing?
We will try to offer possible causes but a bit more info would be helpful.
Good Day!

Re: leaky rear main,what else is new
 

Are you sure that it is the engine that is leaking. It could be transmission oil.

Re: leaky rear main,what else is new
 

Long shot, not dictated by the facts given, but did you put a paper gasket between the engine and the flywheel housing? This gasket seals the end of the cam. As others have said, contact the rebuilder before you do anything.

Charlie Stephens

Re: leaky rear main,what else is new
 

yes Charlie, did put the flywheel housing gasket in ,thank you,this leaks from the rear of the main cap ,I believe slinger trough to be overflowing only on these cold starts.

Re: leaky rear main,what else is new
 

having trouble posting my entries ,bear with me , thanks

Re: leaky rear main,what else is new
 

okay try this again.use 10-30 oil,tried 5-30,straight 30.low on dipstick,high on stick. 60 lbs comp each cylinder,new oil filler tube,new cap. drilled rear main, new drain tube ,welch plug. bearing .0015 thrust .005 thanks

Re: leaky rear main,what else is new
 

I don't suppose you'd have any picture of the rear main to show the oil grooves?

Hopefully you used a babbit guy that knew how to cut the grooves correctly.

Re: leaky rear main,what else is new
 

im on a roll now. acts as if drain system plugged. its not.cold start leaks badly no matter how long it runs. restart in 2 minutes no leak no matter how long it runs.

Re: leaky rear main,what else is new
 

thanks tom, I wouldn't have apicture of the grooves. however there is on caveat. the cap has a hole drilled thru to the galley midcenter of the bearing.I thought about blowby thru that hole some how ,but that doesn't explain the cold engine leak and warm engine not.

Re: leaky rear main,what else is new
 

I would start by fixing that hole.

Who's brainstorm was that?:confused:

Re: leaky rear main,what else is new
 

Re: leaky rear main,what else is new
 

would love to see if the babbitt grooves go all the way to the end

i think the hot and cold is a red herring; something else is going on

Re: leaky rear main,what else is new
 

Maybe cold oil, being thicker, can't drain back to the pan fast enough due to a restriction. But warm/hot oil, being thinner, can flow back faster even through a restriction.

Re: leaky rear main,what else is new
 

Thanks guys for your replys. First grooves do not go to ends of bearings only to wells. new tube,drilled cap so shouldn't have restriction. Tried 5w30 and leaked worse on cold start hot engine no leak so don't thick viscosity is issue. Yeh I think I am going to plug that dang hole. Thanks again for all your help pretty discouraged.

Re: leaky rear main,what else is new
 

Take the weltch plug out of the rear main cap and run a drill bit or burr ball in there. I think the pipe is in to far or it is plugged. You need a full hole through there. The oil groove should stop at the wells.

Re: leaky rear main,what else is new
 

Thanks George this is an early cap and I ran a 5/16 drill through. The tube is an 1/8" lower than the galley an its the 3/8 drain tube. I have an after thought is air getting down the center cap and keep it full air and keeping the oil from getting thru but doesn't explain cold start and hot start.

Re: leaky rear main,what else is new