Hello copper top and so sorry for the long period without an answer. How I missed your post is anyones guess. Judging by the date of your post you may already had your problem remedied. If not I suggest calling your landlord and telling him about your radiators. It sounds like whoever is in charge of starting your system did not go through the building and check the system.
It is the responsibility of the landlord and/or the contractor who maintains the system to be sure the lines and radiators are properly drained and purged. Without seeing the system in person your description seems to be a water logged radiator.
Work hard, Play hard, Sleep easy.