if it over heat when going up a hill or when you give it a bit i dear say you either have a blockage, leaking head gasket still or the system wasnt bleed properly when filling cooling system if it just gets hot for no obvious reason the temp sensors may be conteminated try removing them and giving them a buff so there nice and clean or replace them. There will be 2, 1 is for the gauge the other will be for the ecu. once you have done this the cooling system will require bleeding again