Unidentified Coolant Leak

[jakestachel34]

My dad and I started to replace my water pump on my '07 x5 4.8i and we had to stop because of an outside issue. We had all the hoses off surrounding it and we put them back on while we were reassembling that area. After we were done reassembling, I went to put coolant back in it and after I filled it up to the max line of the expansion tank, it instantly started pretty much pouring out of the back of the engine towards where the engine meets the tranny. Would anyone know where the coolant would be leaking from? When I look into the bay there is absolutely no coolant where I can see, and there is maybe one or two drops on the front of the pan at the bottom. We're hoping it's not the head gasket, but I'm kinda guessing its the valley pan leak. Any help would be appreciated.