Our newish (about 7 months old) Main Eco Combi Boiler has started making a loud high pitched 'wail' about 10 minutes after the heating comes on. It then comes and goes throughout the the time the heating is on. We live in a 4 bed house, most rooms had radiators installed at the time we got the boiler. It stops when we turn the hot tap on for a few seconds in the kitchen. Pressure is at normal level. Any idea what it could be? Also makes loud clunking noises every so often but this may not be related.