Coolant problems on 2007 Chev Impala V6

So can you see any coolant smoking out the tail pipe?You can try renting a coolant pressure tester and pressurizing the cooling system and looking for leak. Thats your best bet if you cant find one then you can get some coolant leak dye add it to the coolant. Then get a black light and look for the leak with the light.

The same suggestions I said before try renting the coolant pressure tester to pressure test the cooling system and watch for leaks when its cold and not running. Try auto zone they rent those pressure testers. If you cant find it like that get some coolant dye put it in the coolant and when the colant level. Goes down then get a dye light and look for the leak. If nothing there then rent a chemical head gasket tester auto zone rents those to check for the head gasket possibly leaking. Let me know what you find.

Alright keep me posted.