I recently changed from oil heat to gas. All the radiators work in my 2 story home except for one on the first floor, which heats 2 out of the 14 posts. I changed the valve, which didn't work. Then I took it apart and ran water through it and the water went through it OK. When I put it back together, still only 2 of the 14 posts were heating up.

What could be wrong and how do I fix it?

  • 2
    Which two? First (inlet end), last, separated, always the same two?
    – DJohnM
    Nov 17, 2013 at 2:13
  • Pictures? Before the change in heat source did the radiator work fully? Is there a steam trap and when was it last replaced? See also diy.stackexchange.com/questions/11129/…
    – Bryce
    Nov 17, 2013 at 6:24
  • A radator has 4 corners that the pipes can connect two, please say where the inlet and outlet pipes connect and where the 2 ok posts are.
    – Walker
    Jan 16, 2014 at 14:11
  • 1
    Is it a steam or water system?
    – Walker
    Jan 16, 2014 at 14:11
  • 2
    If it's a water system, have you already made sure there isn't any trapped air in the radiator? (Especially since you said you'd dismounted it.) There should be a vent valve near the top on one end or the other; when opened a bit it should leak water, not air.
    – keshlam
    Sep 14, 2014 at 14:26

1 Answer 1


I am assuming it is a steam system? Verify that the radiator is installed with a slight pitch, the inlet pipe side should be slightly lower than the exit. If there is a vent installed you should hear a hiss as the steam forces the air out and lets the steam in. The hiss should stop when the steam reaches the vent. If you can remove the air vent and shake it, you should hear a rattle that is normal. You can clean them by soaking in CLR to remove the scale or just replace it. They cost about $15 at the big box store.

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