A weep at the tell-tale hole, a bearing rumble or a belt that squeals only when cold are the classic symptoms of a pump at the end of its life.
Pumps are matched to the engine code and to the accessory drive layout, and on many engines the pump is driven by the timing belt and must be replaced with it. A pump with a different impeller design moves a different volume, which shows up as a heater that is weak at idle or a temperature gauge that climbs in traffic. Metal impellers outlast plastic ones but are not automatically correct for every application.
Listings state the drive type, the impeller material and whether the gasket and housing bolts are included. Replace the thermostat and the coolant at the same time; the labour is already spent.
