hey! my car is having bouts of fever. the temperature gauge started flucuating earlier today, so it'll go up, then down, then up then down again, then hold pretty steady in the middle. now i don't think it's headgaskets because 1) already been replaced once, 2) no coolant disaperaing, 3) over flow tank full of nice green coolant and no oil, and also because the engine isn't even hot. nor is the upper radiator hose, just midly warm. and the heater works quite well. i replaced t-stat a week or so ago w/ a 180* one, and i didn't get a good seal on the t-stat housing so it's leaking a bit there. also, when i checked to see if engine was hot or not, there were bubble coming up the overflow tank?