it could just be air in your overflow hose down to your sump.....once the air is worked out, back the way it was, it should go back to being quiet....i wouldn't get bent yet. try to clean everything a bit and see if you can help get the hose filled with water.....might even want to look at your return pump. make sure enough water is coming into the main tank.....the only water that can go through the overflow is water coming to the tank.....maybe not enough water making it up there?