Harold Kestenholz
Steam radiators sitting on a floor for many years settle into the floor. If it is a type of radiator with a vent on one side, moisture from the vent, slowly over the years, softens the floor at that side a little more and lets the radiator sink further.
Water lying in the bottom of the radiator is picked up and slammed against the inside of the radiator making a bang. This can also happen to water in the steam pipes as the building settles. Picking up one side of the radiator slightly and shimming it can make the water drain better, but it also can loosen old pipes and create steam leaks.
Correcting this problem is the responsibility of the building management. They may not know how to solve the problem and put off making their tenants happy. A knowledgeable Licensed Plumber will be the most likely person to know how to do these repairs safely. Introducing one to the management is a start.
