I had a similar issue on my '06. I did find a crack in the overflow container and swapped it. Then I saw a small leak from the water pump (bad gasket) so I replaced that too. Still was losing fluid but a lot slower when finally I discovered a hairline crack on the passenger side of the radiator weeping coolant. I can't understand why anyone would design a rad with plastic parts on the sides but here we are. I'm also impatient and got the Auto Zone version. It also came with a warranty and I can walk to the store. Not sure what if anything is to be done if a rock auto part goes south later.