I agree with eveyone else pretty much but my guess is the reason the hose is going hot then cold is simply the opening and closing of the thermostat, next thing is where are you taking your sending unit temp off at? Tech helped me solve my issue on this, if its at the top of the manifold in a potential air bubble it could be measuring steam and not water. Next thing is whats to hot? I have read a zillion articles on this and all the older rodders tend to think 220 is way to hot when actually many of the newer daily driven vehicles are running that temp all the time to burn off carbon. On another web site the general answer was if it ain't pukin' water your not to hot, I don't know if I agree or not but with the newer lubricants that clearly can take hotter temps this might be better than running to cold, but you better make sure your cooling system can handle the pressure, the more the temp the more the pressure they are pretty much married together depending on altitude, your anti freeze also increases your boiling point as well but the higher the pressure the higher the boiling point also, if you operate high temps you have to make sure everything else can handle it as well.