Water pumps are the part that continuously pumps water mixed with coolant throughout your vehicle's engine so it doesn't overheat. They can leak and the bearing can become faulty resulting in serious damage to your engine. Water pumps are driven by your cars timing belt or fan belt. If your pump is faulty you should replace it immediately and also replace any belt that drives it to avoid further damage and additional cost. If your Water Pump is driven by the Timing Belt, then you will need to replace the Timing Belt too, as they cannot be refitted.