Catastrophic Coolant Leak 2.7t
 

Hello everyone, i'm a new member here and introduced myself in the new member section, as well as posting a list of the Volkswagens and Audis I have owned.
Well now that I'm having trouble with my 2003 A6 2.7t I am chagrined to see it described as the most maintenance hungry engine ever. That said, I have a puzzler on my hands
I was sitting in the drive-through and when receiving my food pulled into a parking spot to eat. as I pull into the parking spot the engine stuttered and steam begin billowingfrom under the hood. I was able to exit car in time to see every drop of coolant purged from the bottom of the engine compartment in about 2.7 seconds, 2.7t seconds that is.
After this I was able to crank the car once it ran a little rough and I have not started it again. When I pour water into the expansion tank it pours out of the bottom of the engine compartment before I can count to three.
At point I have removed the expansion tank. If I pour water into the hose that feeds the water pump it seems to either run down the oil pan and off on the passenger side or run from above the oil pan, pouring down to the passenger side. If I pour water into the return hose this to the expansion tank none leaks out .
Does anyone have any idea what this may be? Is it safe to perhaps surmise that the leak occurs before the thermostat? Is the thermostat after the water pump? I understand from reading that the thermostat is located On the passenger side of the engine.
I should also mention that the expansion tank seems to be a bit rust stained. Having read about the coolant return pipe on the back of the engine rusting through the thought had crossed my mind, hence my pouring water into the expansion tank return hose. Since None leaked out, am I safe in ruling out this return pipe? Seems to be water leaks out too fast for the leak to be very far from The expansion tank .
Thanks in advance for any insight.