There are two ways to test the water pump for proper operation without removing it from the engine. A defective pump must be replaced without fail. Both a new and a refurbished assembly can be used as a replacement.
The water pump is equipped with control (or ventilation) holes. If the oil seal fails, coolant begins to ooze out of the holes. Have a flashlight and a small mirror ready, then remove the timing belt cover. Use a flashlight and a mirror to locate the inspection holes on the bottom rear/bottom of the pump and check for coolant seeping through.
If the pump shaft bearings fail while the engine is running, a howling sound may occur at the front of the pump, which should not be confused with the whistle emitted by the drive belt when the belt tension is loosened. Bearing wear can be detected by the presence of play when the pump pulley is wiggled (don't forget to turn off the engine first).
Sometimes pump wear does not appear outwardly in any way, therefore, during the overhaul of the engine, it makes sense to disassemble the assembly and visually assess the condition of its internal components. Often the efficiency of the pump is reduced due to severe corrosion damage to the rotor blades.