air lock in hot water cylinder coil?

[leertodd]

Yes it’s an air vent

You sure your not hearing flow noise turn the pump down does it still happen

Might be Because the pump valves are full flow where as before they were restricted ?

Im 99% sure its not the pump sound. just heard that sound of air/water moving at the boiler. will give it a poke later once cooled down. The pump valves were fully open before so put new in the same