1. A malfunction in the coolant pump can cause serious engine damage due to overheating.
2. The coolant pump has a vent hole. If a pump seal fails, coolant leaks through this hole. In most cases, you will need a flashlight to find this hole on the pump. You should inspect the space behind the pulley just below the pump shaft. Slight gray discoloration around the vent is normal, while dark brown spots indicate a problem.
3. If the pump shaft bearings fail, a howling sound may be emitted from the front of the motor during operation. Bearing wear can be felt by the radial runout of the pump pulley. Don't confuse a slipping drive belt that causes a squeal with a pump malfunction. Apply a special compound to the belts to eliminate the belt from the list of possible sources of noise.