Cooling system, 94 grand am

Bizarre question. I had water that seemed to be leaking out at my water pump so I changed it. Now, it’ll run until the engine gets warm and won’t leak anywhere until I turn it off, then it leaks out profusely at the heater core. what’s going on with this thing?

also, I’m getting hot air when i turn on the heater

It is noraml for pressure to build up when the engine is shut off; the residual heat cannot get out because the circulation has stopped. You must have a small leak in the heater core, so that when the pressure builds up, it starts leaking. That leak is not the fault of your water pump. You could have a dirty cooling system as well. If your cooling system has not been flushed in the last 40-50,000 miles, you should have it done. The heater core will likely have to be replaced, unless the leak is at the exteranl connection. Neglected cooling systems can be quite unforgiving.