The failure of the water pump can lead to the most serious consequences, up to the complete jamming of the engine as a result of overheating.
There are two ways to test the water pump for proper operation without removing it from the engine. A defective pump must be replaced with a new one or a refurbished one.
The water pump is equipped with control (or ventilation) holes (see illustration below).
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. Using a flashlight and a mirror, look for the inspection holes on the bottom rear of the pump and check for liquid seeping through them.
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).