WE HAVE AN EHEIM 2213 THAT CONTINUOSLY CHATTERS. I HAVE REMOVED THE IMPELLER, SHAFT ASSEMBLY, AND THE WEDGE. I HAVE ALSO CLEANED ALL THE CAVITIES AND REASSEMBLED. IT STILL CHATTERS. THE SHAFT, IMPELLER, AND SHAFT HOLDER RUBBER DOO DADS ALL SEEM FINE. COULD IT POSSIBLY BE AIR THAT IS CAUSING THE CHATTER AND IF SO WHAT IS THE PROPER WAY TO GET RID OF THIS CHATTER. THANKS FOR ANY IDEAS........HOUTEX.