Once you drop to temps that low then arent glycols starting to get really thick? That would take a very strong pump and possibly a custom made block as the orifices may be too small for the thickening glycols. A car doesnt have a problem because 1. The water pump is belt drive by the engone and 2. The tubing is much bigger than you will find in a computer setup so the thicker fluid would pump much easier. I think the Antifreeze at -40 would burn the pump up. As far as Ethanol mixtures, you can find seals and gaskets that are compatible with Ethanol such as Neoprene, Teflon, Polypropylene, Nitrile, Viton, etc. HERE
is a page showing some chemical resistances of certain materials.
Edit: What about Acetone? Isnt that used as a Dry Ice medium when DICE OCing?