If you mean gasket, i'll assume you mean head gasket. If this is broken you would likely see oil in the water, or, water in the oil. Before you change, have a compression test done. If the gasket is broken compression would be low.

Also you should check that the thermostat is working. If it isn't then the coolant will not flow to the radiator. Also have you checked that the radiator cooling fan is working properly? Check all of this before having the head gasket changed.