ZAP, this doesn't really make sense "and IF the impellers on the hot side have failed and gotten into the motor, you would have heard a lot more than a scraping sound. The motor would be much noisier as the pistons would be damaged." The hot side of the turbo has a turbine wheel and it wouldn't damage the pistons as this side of the turbo is on the other side of the exhaust valves. How can anything get back to the pistons from that side? If it was from the compressor side, then yes maybe.