Hello. Thought there might be someone on here who can diagnose what half a dozen British Gas engineers can't. Our Response 120 has (for the last couple of years) made a very loud rumbling noise from time to time. It usually happens if you switch the hot water tap on in any of the rooms. Now and then it happens when the heating is on. Starts rumbling for no reason (no tap has gone on, no rad valves have been opened or closed). Turing of the tap or turning off the boiler and back on again (advancing the program) fixes it instantly. It will usually happen half a dozen times each day. Sometimes it stops of it's own accord even with hot water running, sometimes you have to turn of the tap. If it starts because of the radiators (no taps on) then it doesn't stop on its own. for your pleasure I put a video on youtube. It stops at the end because the hot tap was switched off. This boiler has been serviced recently. when the boiler rumbles it must also break its seal slightly since CO is produced (enough to make a CO alram in the cupboard flash for a few seconds). the flue has been checked and British Gas said it's fine to use. Any ideas?
http://uk.youtube.com/watch?v=yJ5vdgtBYBU
http://uk.youtube.com/watch?v=yJ5vdgtBYBU