installes a new thermostat why would water leak out?

No! I did not have it tighten enough in the beginning when I put it in. But, my uncle just informed me that the auto store gave me was wrong part. It actually was a little smaller than the original one I took out. So, we are going to change it out and see if that works. Thank you for responding question. I am new to all this.

not sure what you mean by to small?you need a 192-195 degree thermostat and o'ring and that's it,unless you are replacing the water outlet also?