hey all of you lovely helpfull people ,i have just changed the diverter valve diaphram on my wocester 240 combi, thanks to your very informative questions and answers on here ,i have gone around and bleed all my radiaters after about an hour of running ,but after about three hours of running the boiler start making some scary noises ,its like a heavy car engine running ,or like it will explode any time ,does any one have any sugestions as to what might be the problem ,.thanks very much in advance.