if it is filled up to the max and still disappearing...then you do have a leak...and if the coolant is coming out from the top of the radiatorand you did not spill it...then the radiator is cracked at the top where it is joined together...so its time to buy a new radiator and replace it...and overfilling the radiator would not cause it to come out on top of the radiator..it would go into the resevoir and out from there....































**just go to a auto parts store and ask to see how much it is...it should be about 100-150 for the cheapeist...and no...radiators dont last as long as the life span of the car....