Pump noise when air temp drops

[jeepercrna]

Hey everybody I have a tristar pump that mAkes a high pitch noise but only when the temp drops into 30's. Replaced motor this past June under warranty because the bearings went bad. This noise is completely different. Any thoughts?


Jeeper

 

[zea3]

My first pump did that for about 6 years. Never figured out why. Mine finally died when the bottom casing rusted out. Have you contacted the manufacturer about the noise?