[FWB]

run it and when you think its up to operating temp feel the radiator hoses and the radiator.....are they hot? if no then the thermostat isn't opening if they are hot too then there is probably a leak somewhere such that the cooling system is not getting pressurized causing the overheat and the tank to pee. you'll need to pressure test the cooling system and find the leak as it may be in the motor not just externally.