One radiator bleeds well but no heat from it

jbct99

Hello- newbie here.
I have an old domestic oil fired boiler. Plenty of hot water and heat out of all the radiators except one. House is a Cape. Circulator pump works fine, pressure is 17. On the second floor, two of the three radiators heat up. The third one bleeds fine but doesn't fill with hot water. Valve near the floor opens and closes freely. What could be the problem? How can I fix it?

Update- whatever the problem was, it fixed itself. I suspect a blockage. Radiator is now heating up like the others. Thanks for all the comments.

EdTheHeaterMan

Blockage. or insufficient pressure difference between the supply and the return on the radiator

bburd

Are these old style cast-iron radiators, or fin tube convectors? If the latter, the heating element needs to be pitched slightly up in the direction of the air bleeder. I have seen these installed dead level or pitched the other way, and they wouldn’t heat until re-pitched or a second bleeder was installed on the other end.

EdTheHeaterMan

If this is set up as a one pipe around the basement (Crawlspace) with Diverter tees, that may be the last radiator on the circuit, and the house settled, and there is a restriction on the supply or return or in the radiator, you could have insufficient pressure drop between the radiator supply and return. To over come these problems without taking everything apart to find the problem, you might be able to add a pump to just that radiator with a thermostat to turn it off and on based on the room temperature near that radiator.

STEVEusaPA

Maybe the valve is actually closed and not working, or maybe your pressure gauge is reading incorrectly.