1994 Pontiac Firebird Loosing water and don't know where.

When you replaced your radiator did you also replace the cap? Apparently, the factory caps on late model firebirds and cameros are absolute crap. I had had the same problem with water loss but no apparent leakon my 99 bird, luckily my brother who owned a 99 camero had the exact same porblem and eventually realized that his cap was failing when under pressure. Long story short we both bought new caps from autozone and completely fixed the problem on both cars.

On the LT1 5.7L V8's, check the water pump. On the lower drivers side of the pump is a weeping hole that will leak when the pump is shot. The important clue is the car 'missing'. The pointy heads at GM, in their infinite wisdom, put the weeping hole directly over the opti-spark distributor and on the '94, this #$&%@*! Thing is not vented to remove moisture. Hopefully this is not your problem as this is a real pain to correct. Good Luck.