Engine temp going high, coolent overflow in coolent tank

I already disscussed to you, there is no leakage in cooleny. But after I going in 100 speed coolent going to coolent tank and over flowed, due to overflow coolent level reduced in radiator so engine temp. Going high, already I changed pump and radiator with mechanic, finaly he dout in engine gasket, but engine run smoothly, please tell me what this problems.