I have a central heating system on a timer, and whenever the timer turns on or off, for around ten / fifteen minutes, some of the radiators in my home make regular clicking noises, kinda hollow-sounding, coming from inside.

I've done some research and it seems that it's something to do with the hot and cold combining and something growing, shrinking, or similar.. is that correct?

I've already bled all of the radiators and there's no excess air in them.

What else can I try?

  • I fixed a particularly annoying radiator once by whacking it with a hammer in just the spot the click was coming from. That was probably a bad idea, but I got away with it. Mar 26, 2013 at 14:22

3 Answers 3


This is the sound of metal pipes and radiator components expanding and contracting. As they do so, they rub against other fixed parts, like wood framing, brackets, etc. If they stick slightly, you'll hear a popping or clicking sound as they stick and unstick from the friction against this expansion and contraction. So the solution is to locate any points that are making sounds, ensure they have space to freely expand and contract, and eliminate any points that may stick by either changing how it's attached to the structure, or changing the materials to eliminate the friction.

  • That's quite a high-level answer, I'd have absolutely no idea how to do any of the things you suggest. How would I know if the area has space to expand and contract? It's inside the radiator, and I'm not at all comfortable with taking it apart (if that's even possible).
    – Luke
    Mar 26, 2013 at 14:59
  • 2
    @lukech to be fair, it's a pretty high level question, too. Had you posted a photo with an arrow pointing to a specific location the sound is coming from, someone may be able to suggest a more specific fix. From your question, I don't even know what type of radiators you have, so it's impossible to suggest what can and cannot be taken apart.
    – BMitch
    Mar 26, 2013 at 15:50
  • They're just standard metal radiators, really. Hot water comes in, they get hot, etc. If you have any specific questions I can try to find out anything that might help.
    – Luke
    Mar 26, 2013 at 16:13
  • @lukech Not sure which standard radiator you're referring to, there are quite a few. You mentioned bleeding them, so that rules out a steam radiator. But there are also single piece cast iron types, baseboard styles, and a style similar to a baseboard heater that has small metal fins but a large cover with adjustable vents that I'm aware of. Searching around, there are also various wall mounted varieties. The specific question is where is the sound coming from.
    – BMitch
    Mar 26, 2013 at 16:55
  • There's nothing adjustable about it except the valve and the temperature sensors. I think it's a double convector, if that helps.
    – Luke
    Mar 26, 2013 at 17:28

As the radiators heat and cool, they expand and contract. During this process they rub on the brackets that they are hung on. There should be small nylon horseshoe shaped inserts fitted into the brackets before the radiators are hung. This allows the radiator to slide quietly. Often they inserts split/deteriorate or fall out during maintenance. The answer is to take the radiator off the brackets, replace any missing inserts and rehang. https://www.compass-plumbing.co.uk/spare-anti-vibration-plastic-inserts-for-compact-radiator-brackets

  • While this is accurate, it doesn't add anything to the answers that have already been here for years. Well, nothing except a link to a website that you may or may not own. One might be tempted to think of this as spam.
    – FreeMan
    Jan 13, 2021 at 17:42
  • 1
    I disagree. None of the other answers made any mention that radiators should be hung on nylon inserts that are intended to prevent this noise. Jan 24, 2022 at 5:46

It sounds like the clicking noise is not the radiators, but the pipes expanding and contracting. The clicking noise is sometimes due to the pipe moving in the clips that are holding it, or maybe where the pipes are touching a joist and making this clicking noise when it expands when the heat comes on. I’m suffering from the same thing myself after a new installation of gas heating system........very very annoying...

  • Reminds me of the last place I lived that had radiators. Simply the heating of the water in the pipes sounded like someone on the other side of the wall was pounding it with a hammer. Eventually I got used to it as there was nothing I could do about it.
    – SDsolar
    Apr 26, 2018 at 1:33

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