[Mr.Nickey Nova]

GM sells a product called (Cooling System Seal Tabs) part# 12378254. Used it in my 05 pickup when i had a little coolant leak, couldn't tell where it was coming from,possible head gasket. Worked like a charm and that was five years ago.It's made out of some kind of vegetable formula that seals minor leaks. You can get it at your local Chevrolet dealer, give it a try...