My 06 Malibu- 4 cyl. has the cooling fluid needing to be refilled every 4 days. Chevy dealer mechanic said its the early start of a head gasket failure. My personal mechanic tested the radiater with the wand that is used for emmisions tests. He said he is not noticing any high level of exhaust gas in the radiater that should be in there if it was a head gasket. I think he check the CO2, only .12 parts /million. Whats going on? Do I need to repair the gasket or drive it till it gets worse??