Hello, can anyone advice me on my Vaillant Ecotec plus 415. The boiler starts up but switches off after a few minutes. If the temp dial is turned up then it makes a very loud banging and flapping sound. I was advised to get system flushed by one company and another said the boiler is old i should replace it. I dont know what to do. I have purched 2 oil radiators to keep my son and i warm. I cant afford a new boiler but i dont want to spend £600 getting it flushed if that turns out to be a waste of money. Either way everyone is booked up until next year. Can anyone advise please ?