I have not had this situation and can not tell you, but if this sound is not characteristic of the normal operation of the radiator then there is something wrong with them. So maybe the plumber should also look at what happened there. You have to be careful about everything, it may be some small breakdown, but it can cause a big one. Do you know the story about the huge computer breaking down? Scientists built a huge computer, like the first one in the world, and it took up an entire room. But then a butterfly flew inside the computer and everything broke, and the scientists didn't know what happened. What I mean is, it's better to fix it now than to fix it later, when it's worse.
