A failure in the water pump can cause serious engine damage due to overheating, and if a failure occurs at the pump seal, coolant will leak from the weep hole(s). Using a flashlight, look for traces of coolant residue or dried coolant tracks around the weep hole(s). If the shaft bearings fail, there may be a howling sound near the water pump while it's running, and a quick performance check can be done by making sure the coolant level is full, starting the vehicle and warming it up fully, turning the heater on in the passenger compartment, and checking for little or no heat output. A water pump may still be due for replacement even if it's not leaking or making any noise, and the only sure way to tell is to remove the pump and examine it closely for a loose or corroded impeller, a leaking shaft seal, or a worn shaft bearing.