Not 100% but I think if the heater core was leaking then it would leak inside the vehicle. Check one of the sticky posts for "lower intake Manifold" or "LIM". I don't know if it applies to 97s (but i think it does). Generally the LIM leak leaks at the sides (front and back of the engine block - or left and right sides of the engine as installed transversely.) I've changed my water pump twice on my 99. It leaked a lot of fluid but it wasn't hot enough to be steam. There are a few coolant hoses to to check as well.