Back in January I had this car come in. The belt slipped off, shredded and went through the crank seal, into the oil pan etc etc.
I put a new crank seal on, removed the pan, cleaned all the crap out, new belt. Yesterday, 7 months later, 2600 miles later it came back. The front crank seal is not just leaking, but pouring. So I pull off the crank pulley, everything looks fine. No damage, no gaps, nothing. So I installed a new crank seal. I used the bmw tools to remove and install the seals. I used the proper primer and sealer to fill the grooves on the side and it leaks just as bad.
The weird part is, it only leaks after driving. You can Rev it up on the lift, let it idle for an hour and not one drop. But, drive it just around the block and it's dripping on the floor. I'm stumped... any ideas? I would think if the crankshaft had play, you would hear it. Obviously the large center bolt isn't loosen or it'd be out of time. This is going to drive me crazy all weekend knowing this car is sitting on my lift waiting for me on monday.

 

I have nothing to help you but would love to know how this turns out. Please post and update

 

After spending 2 days losing my ass on this car (screw flat rate pay lol) it turns out, there's a small unnoticeable flat spot on the snout of the crankshaft hub. I found this by using a micrometer and taking multiple measurements around the hub. However I'm 100% certain a rubber belt coming in contact with a hardened steel crankshaft for 10 seconds couldn't have caused this. Based on the amount of oil present under the car on the original visit, this problem was already there. They just wanted it fixed for free because they paid for an oil filter housing, valve cover and oil pan gasket. (Which were all leaking as well as removed for removal of belt debris) Next time I'll pull out my micrometer and straight edge to measure and check straighteness of every surface I touch lol.
Either way, there's your answer

 

Was the oil passing between the crank end and the pulley?

 

trying to reconcile that with The 7 months and 2600 miles.. gap. How could have the car survived that long and still be pouring