Hello, I have an 02 WRX STi and am having overheating problems. The temp gauge sits fine for almost 1km and then just goes straight up to the red. When I open the bonnet I have some water spraying up through the overflow and have lost some water but theres no leaking. My uncle has been helping me and hes gotten rid of the air pockets but its still doing that, hes thinking it may be the head gasket, what do you guys reckon? And how can I check the head gasket? Any help would be greatly appreciated.