Radiator Air-Noise - or not???

[hashamyim]

Hello,
So, I have a weird situation...
- My apartment (fourth / top floor of the building) has four radiators, two at the front and two at the back.
- The two at the front don't make any noise when turned on
- The two at the back however, do - specifically the one in the bedroom (which keeps me awake) and in the kitchen (room next door). I think they are somehow connected. The noise is like gurgling and I assumed that air was trapped in the radiator, so I installed an air-release valve in both but this hasn't helped much - it only releases air if it also releases water, so that's pointless.

Strangely though, this gurgling sound has some odd properties:

- The gurgling happens in both the bedroom and the kitchen but only if only one radiator is open. If they are both turned on, the gurgling stops completely!!
- Every time you turn the valve off and then on, it sounds like a blob of air is entering the radiator from the main pipe, but that happens even if there is only a few seonds between off and on, which isn't really enough time for air to gather from the system below.
- Bleeding the radiators doesn't do much. It still gurgles.
- When the pressure in the system is increased by the technician, the gurgling gets less, but is not completely eliminated.
- None of the other flats in the building has any gurgling sounds, nor can they hear the vibration of the gurgling sounds from my apartment.

Does anyone have any idea what could be causing the sound?! Specifically, the fact that the gurgling stops if both radiators are on seems to suggest that it is something that could be solved with some valve or other to balance the pressure... but not sure...

Any help is appreciated! Photos attached!

 

[Rossando]

What is airing the radiators?
Is this hydronic or steam?
If hydronic you have traped air and need to purge it out. Bleed it from the valve while it's running from both units that are giving issues. Possibly this could be cause at the boiler if the haven't is not working properly. Sounds like you need a specialist who knows these systems to help you out.

 

[hashamyim]

What is airing the radiators?
Is this hydronic or steam?
If hydronic you have traped air and need to purge it out. Bleed it from the valve while it's running from both units that are giving issues. Possibly this could be cause at the boiler if the haven't is not working properly. Sounds like you need a specialist who knows these systems to help you out.

It is hydronic - but bleeding it doesn't help - no air comes out. Or if it does (which results in the loss of several litres of water from the system), then when I turn the valve off and then on again, another blob of air arrives and it all starts again. It just seems weird to me that the air makes no sound when both radiators are on. That is the part that baffles me. Surely they would just both make gurgling sounds?!

 

[Geofd]

I would shut the system down and change all the vents