So I did a HG job a little while back, now I seem to be losing coolant (water actually). I've run water in it since the HG job, and now it seems like every few days the water level in the rad is down to the fins. There are no leaks, no drips, and doesn't seem to be any contamination in my oil, and I'm not blowing steam out my tailpipe. My temp gauge never goes above half, but I don't know if i trust it. Most of my driving is to town and back, about 10 miles going 55mph, and after 3 or 4 trips like this, I have to top of my radiator. I've got a lot of ideas of what could be wrong, but thought I would ask some wiser minds here, any input would help thanks!