I have a LS 2000 and it did the same thing, the engine would shut down 4cylinders 1st then the other four and cut off. Did some research, the degas tank seemed to be the problem, bought it from dorman, about 100.00 bucks, pain in the but to replace, when I pulled the degas bottle out there was a small crack that would hold water whan it was cold but when it heated up the water would evaporate through the crack causing it to overheat. Replaced the bottle and still overheating, needed to follow the pleeding instructions, did that no problem with overheating. As crazy as it seems, the degas bottle has alot to do with the cooling system. If I'm not mistaken there is a relief valve on the radiator that blows if the water temp gets too hot, that maybe what caused the leak that you saw, its at the front left part of the radiator.