We have a one-pipe steam system in our 80 year old house. Most of the radiators work well except for one in our dining room that makes a lot of noise when it is cooling. I have done a lot of research and have read a lot about water hammers. I am not sure this is a water hammer because the noise happens between heating cycles when the radiator is cooling. It's one or two loud bangs - enough to make me start. I have pitched the radiator, replaced the valve and tightened all connections.

A friend suggested that it could be that the rod connecting the fins is loose and is banging when it contracts. Has anyone ever heard of this?

Does anyone have any other suggestions? Should I try flushing the radiator?