Q: Dealership says water pump needs replacing

With regard to the dealership, or any mechanic for that matter, simply ask for the evidence substantiating the diagnosis and proposed repair. In the case of an alternator, once the drive belt is removed from the engine, and the engine is run momentarily, the noise should completely disappear. That does not rule out other rotating components though (driven by the belt) as the source of noise and so the alternator itself must be examined further. In any event, with regard to the replacement of any component on a vehicle, there will always be available tangible evidence substantiating the replacement if the part is really faulty. If you do not obtain a rational or credible response once you request that evidence, that is your indication that there is nothing wrong with the part. Furthermore, any conscientious, professional mechanic who correctly diagnoses a faulty part will be glad to answer your questions, in any degree of detail that you desire, and provide tangible and understandable proof of the diagnostic. If he or she doesn’t, that is not an individual who has your best interests at heart. With regard to the water pump, assuming the pump is not operating dry, water pumps do not typically make noise. If the pump seal or bearing is failing, there is a weep hole adjacent to the pump bearing and the leakage through that weep hole will be noticeable (not necessarily zero leakage, but rather "excessive"). Any significant leakage (again, other than a de minimus leak) does warrant pump replacement. If you want the engine noise conclusively pinpointed, and then learn of the required corrective action (if any is required; not all noises represent failures), please request a vehicle noise diagnostic and the responding certified mechanic will definitely find the origin of the noise. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.