A turbine blade tip cooling system includes a turbine blade having a tip cavity, a tip rail surrounding at least a portion of the tip cavity and at least one internal cooling cavity. The tip rail has an inner rail surface, an outer rail surface, an end surface and at least one tip rail pocket open at the end surface and fluidly connected to the at least one internal cooling cavity that carries a coolant. A tip rail cooling insert attaches to the at least one tip rail pocket, and has insert cooling channel(s) and a coolant collection plenum for directing coolant from the at least one internal cooling cavity to the insert cooling channel(s).