After several years of frequent use, the combustion fan began to rattle and eventually came loose. Upon inspection, I found that only the rubber mount for one of the shaft bushings had failed. The bronze bushing bearing looked otherwise OK. I searched for a rubber grommet which would fit, and I eventually found one. But the fan was stiff and didn't seem to turn easily. It was one side of the grommet being squashed between the end of the fan cage and end wall, acting like a brake. I trimmed off the excess rubber with a razor knife, and it worked, but made loud screeching noises from rubber rubbing on metal. Liberal doses of spray lube seemed to work, and it eventually straightened out. That also helped to lubricate the bronze bushing.