I am not seeing white smoke coming out of the exhaust like most of these people on youtube I see. and I keep losing coolant. What could be the problem Could it be a head gasket? When my car overheats the coolant in the radiator reserve boils it gets so hot. I put cardboard underneath my radiator to check for leaks no dripping showed. I have heard everything form head gasket to radiator fan to a leaking radiator. Please tell me the possibilities as to why my radiator coolant is evaporating and boiling.