1/2 way up the gage is not hot in the red is, you don't want to run up near the red all the time, 1/2 way is not over heating, if you have a boil over there is a blockage somewhere, most rad or water leak sealers say drain system of all anti-freeze and refill with distilled water and run to seal, then drain and flush, then refill with anti-freeze, most are not compatable with anti-freeze. I might be able to get a gasket kit on ebay make sure it has all the gaskets you need, go over it again and again make sure it has all the gaskets needed.