Rear main???? how can that be?

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wyoduster

wyoduster

live free or die
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I've taken my car for a 3 mile drive for the second time and after pulling back into the garage theres OIL dripping out of the cover on the bellhousing. Newly built engine ,Did it myself,with a 833 hooked to it. All I can think is rear main seal... how can that be? what else could it be....?WHY? any quick fix besides pulling it? I'm really bummed:angry7:
 
You did'nt mention if it was a small block or a big block.
If a small block, before condeming the rear main I'd check the back of the oil pan, sometime the gasket around the main cap can slip.
Good luck!
 
Small block or big block? If small block make sure your oil sending unit, distributor, and rear intake manifold is not leaking from the top of the engine.

On the back of the block there are oil gallery plugs and the plug for the cam. They could be leaking.

On a small block a thin film of sealer must be put between the main cap and block or it could leak. The rear main seal could be in backwards too. When its in backwards it won't leak at idle, only under load will it leak (don't ask me how I know).

I replaced the rear main seal a few years back on my 340 and its 100% bone dry now. So if done right it should be completely leak free.
 
On a small block, they are easy to put in backwards if your not paying attention.
 
Mine was leaking from the oil sending port (bad brass crush on plastic hose for Autmeter oil pressure gage) and from the back of the manifold. Edelbrock instructions for the Aluminum heads said not to use - what a mistake. Eventually leaked from the front and back of manifold to block seal!
 
I had the same problem with my 360 right after I rebuilt it last year. At least I thought it was the rear main because that's where it seemed to be coming from. After I investigated it further I found it was the oil filter adapter leaking. Since the oil was so clean it was nearly impossible to see it was running down from it. It followed the curve of the oil pan perfectly and dripped right from the back of the pan and made it look like it was the rear main or rear pan seal. I tightened the adapter a little more and cleaned it off and it never dripped again.
 
is there a different type rear main seal than the rope seal for a 340?

mine leaked and want to make sure it doesn't then it goes back in
 
fishy68 said:
I had the same problem with my 360 right after I rebuilt it last year. At least I thought it was the rear main because that's where it seemed to be coming from. After I investigated it further I found it was the oil filter adapter leaking. Since the oil was so clean it was nearly impossible to see it was running down from it. It followed the curve of the oil pan perfectly and dripped right from the back of the pan and made it look like it was the rear main or rear pan seal. I tightened the adapter a little more and cleaned it off and it never dripped again.
Click to expand...
I can second that one.Didnt realize it till after the pan was off.
 
WildCat said:
is there a different type rear main seal than the rope seal for a 340?

mine leaked and want to make sure it doesn't then it goes back in
Click to expand...

Get a Felpro rubber rear main seal. I put one in my cars years ago and its been 100% bone dry back there since.
 
Well Looks like it coming from the main or there abouts. So I'm pulling the engine today to fix it. I'm really bummed about it.
I also have a leaking power steering unit. whats up with that???
 
The 273 I had which was a fresh rebuild leaked at the back of the motor. Oil dripping off the bellhousing. I looked at the oil pressure sending unit, back of the intake, distributor, and everywhere up top but never could find it. Replaced the pan gasket and it still leaked. I have pulled the motor for a 360 now but it never got fixed.

I really don't like the seals ma mopar used in the front and rear of the oil pan. Not saying that is where it is leaking but the seals seem cheesey to me.
 
If you don't put a thin film of gasket sealer between the block and rear main cap its gonna leak. Even if you get the rear main to seal up if there is no sealer between block and main cap it will leak and look just like a rear main seal leak. Remember your oil pump is connected to the rear main cap and pumping oil into the engine right where the main cap and block meet. There is a lot of oil pressure there. You need to clean block and rear main cap surfaces with clean paper towels and Brake Parts Cleaner until they are 100% oil free. Then use a thin film of blue permatex gasket sealer. Don't forget to put a very very small film of motor oil on rear main seal and bearing surfaces where they meet the crank. I put a small dab of sealer where the two halves of the seal meet. I mean small dab and toward the outside of the seal; keep it away from the crank. That is how I did mine. 100% leak free for over three years now. And I mean 100%, no moisture, nothing, bone dry.
 
This might be a stretch. But when you pull the motor stick your finger in the back of the crank thru the pilot bearing to see if you come up with fresh oil. If you have a cast crank it could be forced thru the casting. Years ago Wheeler manufacturing had the bright Idea to drill the back of the cast cranks in there 400 BB so they could be used in a auto or stick aplication. The problem was that the cast cranks were to porous and the oil would go right thru the casting and out the drilled hole. I found this out after installing one of these and pulling the pan twice and the auto trans 3 times. For me it was an easy fix i cleaned the crank real good with carb cleaner. filled the hole with JB weld and put a flat expansion plug in the center. Yours with a stick might be harder, if it turns out that is the problem.
 
Yes I put one side in backwards..... Feel like a dumb ***. So its all done now... Just have to finish assembly and drop it back in.
 
wyoduster said:
Yes I put one side in backwards..... Feel like a dumb ***. So its all done now... Just have to finish assembly and drop it back in.
Click to expand...

I hate it when that happens. :)

At least you have the nuts to admit you made you made a mistake. +1 for ya. I guess it turned out to not be too expensive and I'll bet you never do it again.
 
I did that once. I knew how it was supposed to go in just didn't put it in correctly. Wasn't in a hurry or anything. How I made such a dumb mistake I don't know. Took it all back apart, did it over again, been good ever since.

Glad to hear you found the problem though. Lets us know how it turns out.
 
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