Q
Quiz
Still check above .also could be blockage at pipework tee were hot water return joins heating return if near boiler
Did that, also took connections off the coil, both sides, and hoovered out with wet n dry all open ends.
Re-filled and before too long, same old whooooshing sound and boiling water into F&E.
I am now thinking it could be an inefficient pump, after all, that debri had to go through the pump to sit on the 2 port valve???
If I turn the boiler stat right down, it does not happen. But then the water and rads do not get hot enough.