Coolant leak but can't find where.
 

Hello, I have a 2005 Suburban 5.3l non flex fuel that has a coolant leak somewhere and I can't seem to find it. I recently changed my t-stat because of temp gauge red lining.I now have a major leak what seems to be coming from under the water pump but not by the weep hole. I mean when I start the truck it drips pretty good but there is no physical wetness from the top of the engine compartment. I'm thinking that I need to replace the water pump but I don't want to if that is not it. Could it just be the water pump gasket? Also, I was checking out water pumps on line and some say " fits 2.05" diameter t-stat outlet or 1.88" diameter t-stat outlet" and I'm not sure what one I have. If this helps the t-stat was the t-stat and housing all in one. Any help as to what it may be is appreciated. One more thing, I would be buying new as opposed to re-manufactured and would like to know a good brand name. Thanks in advance.