Every water pump has something called a weep hole. The hole is just a few millimeters in diameter and should be located on the side of the pump or facing toward the ground. Normally the weep hole is sealed by a gasket, but as the water pump begins to wear, the gasket will erode. As a result coolant will begin to dribble out of the hole. This is very serious and indicative that the water pump is no longer able to do its job. If coolant should leak out of this hole while the engine is idling, you're best course of action is to head to the closest mechanic immediately. You risk overheating your engine and doing irreparable damage to it otherwise.
