Your Jaguar water pump is probably one of the most important parts of your engine.  The water pump works by circulating the coolant through your engine block, heads, and radiator.  The coolant is there to absorb the engine's heat and dissipate it into the atmosphere.  When the water pump fails, the coolant is unable to circulate and boils in the engine jacket.  The heat is too much for the engine to handle.  The end result is overheating and engine break down.  Three key factors are attributed to water pump failure.  The first is leaky shaft seals.  You'll be able to tell if you have leaky shaft seals by looking for coolant stains around the vent area.  The second reason for water pump failure is noisy shaft seals caused by ordinary lubricant oxidation on the bearings and normal bearing wear.  The third most common reason for water pump failure is impeller slippage.  Because the impeller and shaft are part of a press-fit assembly, this problem will most often arise on remanufactured water pumps.