New system oil furnace.belt driven. When fan comes on geting a brief suction like metal sound on the furnace .. Not terrible but its there. It was suggested to me that i put a vent in the cellar on the return pletenum. Is that a wise thing to do since cellar does get water in it from time to time in the summer and spring? Otherwise its a very large clean unfinished cellar. East Coast where furnace is only used from oct to march or so.