hard to say, i would of said stuck pump or air in h/exchanger hence the hissing/banging boiler not getting rid of its heat.
Your question states any advice greatly appreciated:
start saving for a new one, they getting slim on available parts, they are failing consistently, it will end up letting you down at a most in-convenient time.
plus with gas prices soaring....the boilers only about 65% efficient when in good order. £35 out of every hundred you spend on gas goes outside.
best of luck anyhoo, hope you get the old fella sorted
iain
September 2008
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