All 5sfe guru's look inside, What is causing this leak? Options

[AllTrac96]

Well many many moons ago i started my 5sfe build/supercharge project. It took me nearly a whole year and a half to finish the fully built 5s and get everything i've needed. About a month ago i started it up, ran it for about an hour before driving it checking for leaks and stuff and i had gotten nothing. I took it for it's first test drive and as soon as i pulled into my driveway i looked under only to find a large puddle of oil mixed with coolant a.k.a milky yellow substance. what a b!tch. the whole back of the block glistened and from my initial gander i had thought that i blew the headgasket (mls cometic gasket). it sat for a month again as i continued to work 50 hour weeks until this weekend...memorial day weekend when i went out to look at it and give it a second opinion. i took off the supercharger (which by the way was pushing 12 pounds of boost) off the car and ran it n/a for this test. from what i could now tell where the block and head are mated is no longer seeping, however, where the block and tranny are mated is where the oil/coolant is coming from. i removed the flywheel cover and could only barely catch a glimpse of what was going on as i was getting dripped on. ihave no clue where to go from here im taking anybodys advice and im willing to try anything. also i am not blowing anything out my exhaust and i can see no cracks in my head or my block. i also took it to a local mechanic for a second opinion he ran a test that said it had a leaky headgasket. i am just so confused right now and fed up with the celica i could scream....sorry for the riddiculously looooong post. thanks for reading.

[alltracman78]

How well was the block and head checked for flatness?
MHG are great, but they are much more sensitive to variations in the surface compared to regular HG.

The only thing I can think of with coolant from the trans end is a leaky freeze plug. I don't recall if the 5S has one on the trans end though.
Or it's leaking from the coolant elbow right above the trans.

The oil [from the trans end] could either be a incorrectly installed RM seal, RM seal housing, or the oil galley plug not sealed.

Now if you also have a BHG the coolant oil mix could be leaking from one of the above.

Or a crack[s] in the block.

Have you ever rebuilt an engine before?
Did you do all the work yourself?