The other day I noticed the pump motor for the pop-ups on our pool was louder than usual. There wasn't anything I could attribute this to such as the motor overheating, and the onset wasn't gradual - one day it was quiet and the next it was loud.
The motor hasn't run very long in this state, I shut it off and have only run in a couple times for about 5 minutes at a time to test some things. For instance, it appears to still have full power, as when it runs it is still driving the pop-ups and the force of water coming out appears to be about the same. And it doesn't seem to be overheating, at least not when running it for just a few minutes. (I can hold my hand on it and it feels hot but not uncomfortable.)
I did a bit of research and found a couple of things which possibly could be going wrong here. One is that the could be something that got stuck in the impeller, and the noise I am hearing is the impeller grinding against it. The other is that the bearings are going bad. The noise the motor is making seems like it could be either one: it sounds kind of like a constant metal rattle of moderately high pitch. I had tried listening closely to both the motor itself and the impeller housing, and haven't been able to isolate one or the other as where the excess sound is coming from.
I have tried a quick taking off the impeller housing (it's got a hand tightened screw that holds a metal clamp in place) but both sides of the motor housing are bolted to other things which prevent the housing from separating until they are all removed.