some radiators remain hot with valves off

Bert_4

I moved into an old home with gravity hot water radiators on 3 floors. In the second floor bedrooms, I can control the 2 radiators in one room, but not the individual radiators in the other 2 rooms. One of them even has a brand new valve. I turn the valves off but they remain very hot whenever the boiler is on, and for a while afterward. The radiators in the 3rd room remain cool with the valves off. Any idea what is going on? The two rooms where the radiators remain hot appear to be on a different supply loop.

Plumb Bob

In an old house it is quite common for valves to be stuck so they do not close completely. This does not explain your problem persisting in spite of the new valve. You are probably getting convective flow through the side of the radiator that is not closed with a valve. Gravity pipes are quite large and could allow bidirectional circulation in the same pipe. See if closing the loop off on both sides fixes the problem (you should have a valve to do that, near the boiler, but no guarantees).