Not sure if i have a bad head gasket. The whole topend is about 5 months old. About a week ago when the car is cold and it warms up the temp goes almost up to 270 then goes down to around 160. After that u can beat it and it wont move. So i changed the thermostat to a 180 and now its fine. If you look in the overflow it has bubbles coming out of it but the is no anti freeze in the oil or not smoke comin from the exhaust. The temp stays ice cole now. Just not sure why there is bubbles coming from the overflow.