Auto Air Conditioning & Heater Repair: 1997 audi a6 quattro coolant leak, audi a6 quattro, coolant leak

Question
after installing a used motor from a 1996 a4 s1 my 1997 a6 is getting way hot and leaking coolant at the heater core going into the firewall.is there a procedure to vent air from the system that i evidently didn't follow,also where is the thermostat located?i thought i knew enough about auto repair to be successful at certain endeavors however,this has me questioning all things warm and fuzzy and i am just at the end.not pleasant and stranded in iowa!!

Answer
The thermostat in an A6 2.8 is slightly to the right of the passengers side camshaft in the thermostat housing.  Basically the top rad hose engine outlet beside the waterpump.  Make sure it is thermostatic spring side towards engine and the vent hole is at the 11oclock position.  Temperature is not going to cause a leak at the core but excessive pressure will.  

Wayne