Audi A4 Radiater (?) Problem

My car (1996 Audi A4 2.8, 79K) has been smoking on the drivers side towards the front of the vehicle. The car does not overheat (the temp reads normal, even when smoking). The radiator was full of fluid the first time this happened. The mechanic found a leak in the coolant hose and fixed that. He also pressure tested the radiator and found no problem. I drove home, and it started smoking again. I called the mechanic who said that there was an oil leak and the oil was just burning off and I should not worry. I took the car through a car wash and then parked it at the grocery store. When I came back it was smoking again and there was a large puddle of orange liquid dripping from the same place the smoke came from. I had it towed back to the mechanic. I thought it was the radiator that had leaked, but the mechanic said that the car was full of liquid (radiator too) and he could not figure out where it was leaking from. I just has the tie rod ends replaced and the catalytic converters replaced. Any ideas?