Help is very much needed. I have a condensing combi boiler (Vaillant Ecotec Pro 28) and when the boiler turns on I get about 10 seconds of water trickling through the radiator in the highest point of the system. Some days it’s quieter than others but at 6am it wakes you up!it’s been bled to death. The whole system recently had a full Magna cleanse and Magna filter fitted so the system isn’t bunged up. The LSV has been opened and closed and the noise still persists. Boiler pressure is 1.5 on the electronic dial. Help!