can mean bad head gasket. I hope you're wrong, that it's really light blue that you're not seeing. Who rebuilt the engine? turbos? How many miles on it since rebuild? If it really is white, you can get a shop to do a test for combustion gases in the radiator. It's quick and cheap. ... I'm not knowledgable about water from the turbos getting in the exhaust, but someone who is could tell you about that.