Have just had the pump replaced on my CH system after the Potterton profile 50e boiler failed to stay in. The boiler was drained down for the install and since we have started back we get strong gurgling sounds in the boiler and a noise which can only be described as 'wooshing' through the pump. I assume this is air, Ive tried radiator bleed with little success and all taps in the house are mixer so I can't do the cold mains into hot tap trick.......any suggestions?