Water pumps fail eventually. Usually, the bearings wear, allowing the shaft to move in the housing, resulting in a leak. Use a high-quality replacement water pump, and one that is designed for performance cooling. Many aluminum water pumps are made to reduce weight compared to iron, but don’t necessarily flow well. Flow Kooler builds water pumps specifically to increase flow at lower engine rpm, and also to reduce cavitation which introduces air bubbles into the cooling system.