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Radiator Sounds Like Popcorn

I'm having an issue with a few of my steam radiators that I can't figure out. When they're warming up, they start making a ticking noise, that sounds almost like popcorn popping. It will go on for about 30 seconds, then stop. I had replaced the air vents on a few and that seemed to help for a day or so, but now they're doing it again.

Here's a video I took of it so you could hear the noise: https://youtu.be/2pJM_5ponIU

Not sure if this is related but I think I need to replace the main vent. It's making some pretty loud knocking noises when the system heats up, but I can't see what the size of the vent is to buy a replacement. Any ideas?


  • Jamie Hall
    Jamie Hall Member Posts: 21,092
    That would be irritating. Sounds more like expansion, though -- and the timing is right -- so I would check and make sure all the bolts holding it together are tight, and that it is free to move easily on the supports, and see if that helps.

    Changing the vents won't help knocking noises. Those will either be from expansion or water hammer, and you need to track down which it might be. On the other hand, if the vent itself is making noises it probably does need to be replaced. Main vents are sized by the length and diameter of the main they are intended to vent, so can you get us that information?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ChicagoCooperator
    ChicagoCooperator Member Posts: 330
    Convectors tend to make a bit of expansion noise when they heat up from cold (he says from experience - though mine have lighter weight elements). You could try the tip for radiators and slivers of milk bottle under the vent end unless they are fixed in place. But some of the noise is unavoidable.
  • huntj01
    huntj01 Member Posts: 8
    Thank you both. I tried tightening the bolts but nothing was that loose, and the few I did tighten had no effect on the noise.

    I did notice the supply valve was closed, so I opened it I think completely. Those should be open, right? Just making sure I didn't screw something else up!
  • Gsmith
    Gsmith Member Posts: 423
    yes supply valve on one pipe steam system radiators and convectors should be fully open. This might have caused the sounds you heard, partially closed valve won't let the condensate out, possible steam trying to push through the collected condensate. How's it sound now?
  • huntj01
    huntj01 Member Posts: 8
    @Gary Smith I think that may have done it! I haven't heard the noise since I opened it. Can't believe something so simple was the problem.

    Do you keep opening that valve until it stops or will it unscrew at some point? And the room that radiator is in is tiny, so if it gets too warm in there should I swap out the air vent for a smaller one?

  • Gsmith
    Gsmith Member Posts: 423
    Turn the valve opening knob until it stops in "open" direction, it will not fall off. If the room gets too hot, put a slower venting air vent on the radiator/convector.
  • huntj01
    huntj01 Member Posts: 8
    Thanks again!