When boiler is turned on it makes a banging noise and what sounds like air coming out . Expansion vessel, Heat Exchanger and pump has been changed. Could this problem be Air in the system and requires Radiator bleeding?

Kenny, March 2014

How to change flow and return valve?

Byron, March 2015

''boiler makes banging noises & hisses''

parts changed
heat exchanger
expansion vessel
pump

presumably all work done by a gas engineer

Question

what was the original problem with the boiler BEFORE any parts were replaced?

if the answer is boiler makes ''banging noises & hisses'' I would start wondering if the parts fitted so far were necessary because they dont seem to have solved the problem

what does the gas engineer you have employed have to say about the cause/fault?

if ''air in the system'' is causing the banging & hissing noises then bleed the radiators
but im assuming you would have already done that as its a very simple procedure

hmmm?

banging & hissing noises

parts changed

no difference

there seems to be a critical piece of information missing here to unlock this mystery

i have an idea as to what the problem might be but i would need you to give a full history of the boiler, its faults, which engineer changed which parts, in what order, what if any difference it made

cant help you unless you arm me with the facts

Q, March 2014