A fault in the water pump could lead to excessive overheating and consequential engine failure. There are two ways to test the water pump while it is mounted on the engine. Where defective, replace this with a new or rebuilt unit. The weep (or vent) holes of the water pumps are situated at its side that faces towards firewall. If there is a failure of the pump seal, hole will allow coolant to leak. Once you remove timing belt cover, then need flashlight and small mirror to check for leakage at water pump underneath. In case of falling off, water pump shaft bearings may cause howling sound during pumping process. By removing timing belt one can sense wear when rocking water pump pulley vertically up and down without engine on.