96 mustang coolant leak

Yes, thousands of people have had this problem. The water crossover on the NPI/early PI intake manifolds tends to crack and leak water after a while. Only solution is to replace the manifold. The newer manifolds have an aluminum water crossover instead of a plastic one like what's on your car (assuming it is the stocker). Might as well go ahead and swap in a PI intake manifold, as it's worth quite a few horsepower, and was actually cheaper for me. Search PI Intake Swap and you should find all the info you need.

You can search and find 100's litterally on that subject along w/that some pissed off mustang owners!