actually the hose isnt a steam vent. you shouldnt have steam, but if you do thats that the over flow bottle is for. that line is a vent, but its to release air trapped in the head. with out it youd have an air bubble on top of the head that couldnt be removed with out vacuum bleaind of the coolant system. so yes replace it. its a piece of straight hose that goes into the top of the radiator.