ok, i've added the vinegar to the loop after leaving a piece of tube half-in half-out of vinegar for about 2 hours and observing a reduction in the amount of build-up, reading
http://scifun.chem.wisc.edu/chemweek...ceticAcid.html
seems like vinegar shouldnt hurt much, ocau'er mjolinir said it might not be great for long term use, but i plan to re-fill the loop in the next week or so. I'll let you all know how that goes. MCP600 has been fine for a while now. i dont feel it was warmed by the ambient temperature because the temperature has since been higher and not caused the pump to get as hot as before... time will tell.