There was a small amount of corrosion starting on the rotor hub, but nothing major. The most intense corrosion was on one of the coils inside the motor, probably on the downhill side of the drip from the shaft.
I'm not convinced that just because vinyl has a larger coefficient of expansion than water that you won't get pressure deltas from the temperature swings. A good portion of the water is in the radiator and blocks, and any air in the system will have a large expansion coefficient. Without actually measuring the pressures I would hesitate to jump to conclusions one way or another. I merely brought up the concept that a closed system without a vent to atmospheric pressure may generate pressures on the shaft seal that exceed it's design limits.
I vented my system and am running that second CSP750 pump in there, but it started out making rude noises when I first turned it on so I doubt I'll get any usefull information out of this whether it fails or not. Besides I doubt I'll be able to put up with the noise for long enough, especially when my DDCs arrive tomorrow.
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