Hi chaps, i have a 105e and have had no problems with it at all, until now. When we turn the heating on there is a really loud humming noise coming from the boiler, similar to a jet plane. It quitens down after a few minutes, but as the heating cools down then fires back up, it happens again. No problem at all with the DHW. Did a bit of research and got a friend to fit 2 new 'o' rings (with blue paint on them-part number from baxi themselves) but this hasn't worked, any more ideas would be grateful before i set out and buy a complete new diverter valve. Thanks.