Just bought new pump. My old one lasted for 12 years. New one is 4 months old and recently started to make a loud whine or screeching noise when operating. It works fine but is very loud. I have trouble shot and eveything looks normal.

Most likely the bearings on the motor are going out. 4 months is way too soon, but it is possible you got a lemon. Unfortunately I wouldn't expect the new one to last 12 years. It's possible but unlikely. You should however get at least a few years. If the shaft seal on the motor shaft between the impeller and seal plate failed then water can drip back along shaft and get into motor bearings. This will cause motor bearings to fail. Even if this is not the case the motor bearings can fail even though it is rare to do so within first year. I would contact the place you bought the pump from, or whoever installed it. It should have at least a one year warranty. If for whatever reason this motor is not covered under warranty and you have to replace it, I would consider rebuilding it. Normally I don't care for rebuilds, but if the motor is truly only 4 months old then rebuilding it would be a good option.