i have an 89 firebird V6 2.8L engine. its been running fine until about a week ago when the engine got real hot and the coolent started boiling. the radiator fan usualy kicks in right when i turn on the battery but it has stopped doing that, it actualy doesnt kick in at all. there is also no coolent flowing through the pipes at all and im not sure what is going on. my normal opperating temp is like 180 and my car now reaches 240. could this be my thermestat? or a senser somewhere? help would be greatly appreciated thanks