I'm renting in an old apartment building and we have steam radiators in every room. I'm aware that steam radiators make a little noise when they come on, but the one in my room makes an incredibly loud banging noise when the heat comes on - it bangs so loud that the floor vibrates at times. I had a repairman come in and replace a valve because the heat didn't come on at first, but the banging continued. And I can't seem to find any kind of valve on or around the radiator to bleed it. Can anyone tell me if this 'banging' is natural, and if not, what I could do about it? Thanks.