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Massive oil leak from passenger's rear of engine
For those who don't know me, I'm the idiot that decided to put a T444E from a school bus into my truck. That I just bought with a bad engine because someone changed the oil to flush the gallons of coolant out of the crankcase right before I looked at it.
Fast forward a week and a half of fighting with the truck and a tremendous amount of regret, and it's back together with a slightly more fresh engine. 114K miles from a school bus with rust and a slipping transmission. Went to fill it up with oil, and noticed that it dripped oil from the flywheel inspection cover. Important detail number one. Not a ton of oil, but a definite drip that stopped pretty much immediately after I stopped adding oil.
Everything else looked good, so I fired it up. Started pretty quickly for an engine that hadn't run in forever. Shut it off pretty much immediately after it found idle, as I hadn't filled the radiator, anticipating something going wrong and having to take it all back apart. Looked under the truck, and it was gushing oil. Like if you turned a quart bottle upside down. Said some choice words, put a drain pan under it, and called it a night.
Today, there's probably at least a quart and a half of oil in the drain pan. I started it back up on the lift, let it start to leak, and shut it down and ran the lift up. It's leaking in a steady stream from what looks like the passenger's side rear corner of the oil pan. Now, in the T444E swap, the oil pan is one of the things that has to be swapped over, so the pan was off. I also don't have a engine stand capable of turning this engine upside down, so I had to do it right side up which is a no-no according to International. But I did it as right as possible under the circumstances. The pan was removed, the mating surfaces rigorously cleaned, and the engine was left to drip for several days. Cleaned every day with brake clean to prevent as much oil contamination as possible. It went back together with the TA31 sealant, as per International. Even so, I didn't expect it to be perfect, though I can guarantee that it's far from the worst oil pan job done on these engines. Figured that a slow leak was better than a big orange paperweight taking up room in my shop.
My first thought seeing this leak was that the seal failed, but with the amount of oil that is leaking, I don't think it's possible for it to be the pan seal unless there's something else going on. There would have to be a large hole and a ton of pressure in the crankcase for it to leak this much from between the pan and the mating surface. Again, multiple steady streams. So my next thought was rear main seal. Like an idiot, I didn't replace that when I had the engine out. But again, unless there's a huge chunk of the seal that's just gone, I can't imagine it leaking this much.
What's throwing me off is that it leaked when filling with oil. A lot of the common leaks on this truck don't seem compatible with the way it's behaving. Turbo o rings can't leak when filling, since there's no oil going in that direction when the engine is off. Rear main would be unlikely to leak when filling. Oil pan shouldn't leak when filling, since it would have to navigate the thick layer of sealant, along with the fact that the pan is bolted against the mating surface, while under no pressure at all. Cracked cylinder shouldn't leak when filling.
So my question is, what is on this engine that would A) leak in a steady drip when adding oil to an empty crankcase B) leak like a garden hose when running, even after a few seconds and C) leak from the rear passenger's side corner of the pan.
Hopefully someone has some suggestions, because I've spent pushing 4 grand and a week and a half of labor to have a truck that I still can't drive.
Thanks in advance for any advice.