Water pump

The water pump pushes coolant through the block, the head and the radiator. It is driven off the timing gear or a belt, and on most Cummins engines it sits low on the front of the block, where a leak goes unnoticed until the level drops.

Two faults bring a pump to us. The shaft seal goes, and coolant weeps from the drain hole under the housing, usually leaving a dried crust down the block in the colour of whatever coolant is in the system. Or the bearing goes, and the pulley develops play you can feel by hand, with a whine from the front of the engine that rises with engine speed. A pump that is no longer circulating properly shows as a temperature gauge that climbs faster than it should.

Pumps do not interchange across families, and even within one engine model the mounting face, the impeller and the shaft length change with the build. The number cast into the old housing settles it. If the casting has corroded past reading, the engine serial number will get us there, and photographs from the front and the side help more than a description.