need to keep heater on to keep engine from over heating

i recently replace a heater hose and ever since then if i don't have the heater running on the engine temp goes up to high until i turn the heater on. I can run the engine for a few minutes without the heater running on hot. Then the engine temperature gauge will start moving towards the hot side. Once it gets about 3/4 of the way up i turn the heater on hot and then the engine temp. goes back to normal. Also both fans will turn on and run constantly most of the time.