My car keeps overheating ive changed the water pump, thermastat and radiator. the only place that water leeks from is the resuoivor what else could it be and how can i tell?

You need to find a garage that has a coolant gas tester. this measures presence of combustion gases which have bled into the cooling system, meaning a bad gasket or crack. when the combustion bleeds into the cooling system, it creates pressure which blows the coolant out the overflow.

after you look in that area, check for sweet smell, green or orange tinged white smoke at the exhaust could tell you that the coolant is going into the combustion chamber. when it leaks one way, it often leaks the other way as well when the piston is on the intake stroke.