Weird sound coming from radiator/piping a couple minutes after boiler starts

Don_175

our boiler came on tonight (hadn’t run in hours). Just a couple minutes later, I happened to be walking past a radiator in our second floor hallway which happens to be pretty much directly above the boiler. It was making a sound like air was being sent up the pipes to it at a pretty good volume. It was not air escaping from the vent or anything leaking. It sounded like air traveling up through the pip3, almost like when you’re inflating something rapidly. It was loud enough that I heard it in the next room. No other radiators were doing that. A couple minutes later, it was quiet again. Boiler was still running. It was not a water percolating sound either. Any thoughts on what it would be? In the 9 years we’ve owned our house, I’ve never heard it do that before. Thank you.

109A_5

The boiler's water level correct ?

EdTheHeaterMan

Steam and air don't mix. If a radiator is cold, it is full of air. For steam to enter the radiator and heat it, the steam must push the air out through the radiator vent. Otherwise, the air will prevent the steam from entering and heating the radiator.

The fact that you've never heard this particular noise before may simply mean you were never in the right place at the right time to hear it.

However, I'd be more inclined to look at a few other possibilities. As a system gets older, corrosion can build up inside the pipes and restrict the normal flow of steam and air. Although I have taken apart steam pipes and they were as clean as the day they were new... (as if some one just steam cleaned them). You may also have an incorrect boiler water level, as our friend above mentioned. A pressure control could be failing and allowing the boiler pressure to rise higher than necessary for efficient heating.

All these things can develop gradually, and you may only be noticing them now.

Have you noticed any changes in how the radiators heat? Could your main vents or radiator vents need replacing?

Keep an eye out for subtle changes in the way the system operates, such as rooms that used to be comfortable but are now cold, or rooms that are getting too hot when they never had that problem before. These changes can provide valuable clues about what's happening with the system.

109A_5

I'd see if you can reproduce the event with similar boiler activity. Maybe someone mostly closed the radiator valve or the valve's disk has become detached from the valve stem. Does that radiator still heat as expected ?

I guess it depend on where the sound is actually coming from.