Rear Main Or Oil Pan Gasket?

I can't figure out my leak - and it's HUGE!

I've replaced my rear main 2x, and the oil pan each time I've done that. Yet, no matter what I've got oil running down the bell housing. Probably leaves a 8-10 inch round puddle after every drive no matter how long.

I put some dye in the motor and tried to see where it was leaking from, but it's just all coming up from the same place - rear main or edge of the oil pan. At least the dye showed that it was for sure motor oil.

I've also checked the back of the motor, no oil is above the crank, so its not just leaking from the valve cover or something.

Is there any trick to tell which is the problem? I'm wondering if my oil pan is bent and I just need to order a new pan. That's the only thing I can think of, but thought I'd check here before I wasted some $$$ chasing something else that may not solve the problem.

 

Sometimes these are tough to diagnose without a full set of photos.
Make sure the valve cover gaskets aren't to blame. Make sure there's no crack in the rear of the block.
Is your pan actually supporting the main seal? The seal is often supported by the bearing cap.
Please share make and model of engine as others will have more ideas.

Make sure the pan is bad before replacing it!
One idea: Next time the pan is down...clean everything, put a light layer of petroleum jelly (Vaseline) on the main seal (or bearing cap), temporarily install the pan, do not fill with oil, pull it again and visually inspect the contact area. There should be a uniform transfer to the pan. If not, then maybe the pan is deformed.

 

One tip I heard about was to make sure the PCV valve is working. Apparently they can fail, cause the engine to over-pressurize and force the oil out through the rear main seal.

 

or blow the oil out of the valve covers.btdt

 

The tip from Flatlander and stericlan are definitely something to look into. I had this issue with my V6. The PO had disconnected to PCV sysem, causing an over-pressure, which was forcing oil past my rear seal, especially after long, higher rpm runs. And this was after doing a engine rebuild, and replacing the seal another time. Just took me awhile to make he connection. So yeah.....oil pan sealed, and PCV system working....good starting points.

 

If you’re nicking the outer beveled edge while pushing the seal in that could cause an issue. Did you remove the main cap and loosen the next few down the line? Pre lube the seal? It’s a pain for sure. I did mine years ago and it’s still drips, but barely.

On a side note, it’s there a oil gallery plug on the rear of these straight 6’s?

 

Thanks for the thoughts. I'll make sure to take a look at the PCV valve - I haven't checked that at all yet.

If not, I'll try the petroleum jelly on the pan.

The first rear main I knicked the seal for sure. The second time I loosened all the caps, used the little plastic shoehorn and lubed the heck out of that thing!