Without the fluid circulation created by your Mercury water pump, your car will overheat and wreak damage to the entire engine system. So save yourself some major engine repair bills by checking the coolant and water levels in your system. Inspect your hoses regularly for leaks. The Mercury water pump relies on a belt that is hooked up to the crankshaft of the engine. When the engine is running, the pump circulates fluid. The pump is designed as a rotary dynamic (centrifugal) pump, which is designed with an impeller that forces the coolant fluid to rotate. Under that force, the fluid moves around under its own momentum. The bearings in your Mercury water pump are vital for keeping the water pump's shaft rotating freely in place. You might hear the sound of a bad bearing; it's a growling, grinding noise that comes from the pulley of the water pump. Often, a water pump fails because of bad bearings or a leaking gasket. To test for bearings, take a hold of the ends of the pulley and see how loose the belt is. When you rock the belt around, and notice any 'give', then it is a sign that the bearings have deteriorated. Coolant will leak out of the broken gasket, so pay attention to any spots under your car that appear after you have parked there for a while. Watching for these signs of water pump failure will pay off when you avoid overheating and damaging your Mercury's engine.