Using my Dremel today at a slow speed started to get very very hot rubber side next to motor coil started bubble up stopped it, let it cool down took out brushes they looked fine replaced brushes and ran it at a slow speed with no load on it still got hot, took apart and cleaned all the air vents (not very blocked) reassembled ran with no load again started to get hot again and it stopped never to go again Has anyone had this problem? and is worth buying a new one?,