I don't know a lot about radiators other than I have holes throughout my house where they used to be (even in my marble fireplaces) and I'm not complaining they are gone. But if the landlord has bled the radiators that would seem to indicate this is a hot water system and not a steam system. You also mention it can get much too hot. Maybe the boiler is making steam instead of hot water, that hits your valve and pops. Maybe the boiler can be adjusted down.