Boiler makes a banging noise and then dies

20 Jan 2013
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United Kingdom
All, help pls, no heating since yesterday!

captured the issue on video as below:

- I have removed and tested the air fan, it is working perfectly and as you can see on the video as well. so its not the air fan gone belly up
- water pump (upstairs in the airing cabinet) is working as normal
- its a very loud banging noise so i suspect its not a blocked water flow..
- the flame goes orange as the noise starts (as in video).. but what could this be??

please help..
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We cannot help you because we dont give advice to DIYers on gas or combustion issues.

You should not have opened your Suprima boiler yourself. The advice would be to get a gas registered engineer to check that its safe.

In any case the problem is probably caused by a stuck or non working pump not creating any flow.

You can confirm that because the flow pipe will be very hot and the return cold and no heat going to the radiators.

In any case the problem is probably caused by a stuck or non working pump not creating any flow.


Or perhaps there's not enough water in the system. Check your F&E tank to make sure there is water in it.

Also check that there are no closed valves in the circuit.

Whatever .. for some reason the water isn't being circulated through the boiler and your mission without taking the cover off,like you did there, is to find out why.
Thanks for your analysis and feedback.

I have just climbed the loft and the F&E tank is full.

I have a question though:

As in the video, every time there's a banging noise the flame goes yellow. with the final 'bang' it goes dead.

how can a blockage in the water system cause that? doesn't it indicate a problem in the gas/flame side of things as opposed to the water circulation side of things?


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When it bangs, $hit is disturbed and is sucked into flame.

The burner dies because the H/ex is over temp.

there is water in the tank. if i touch the water pump it seems 'normal' (very slight wirring feel to the hand).

so the next suspect might be the heat ex-changer..

how do i check that the water flow?

from the flow pipe being very hot and the return being cold?


Tested the waterflow with a mate in the airing cabinet monitoring the water pump and valves.

The flow pipe gets blistering hot.

Water pump works though and ultra hot water flows upstairs to the airing cabinet as well.

Yet, the boiler makes that massive banging noise and goes into a 'Boiler temperature control achieved' (blinking green) status. the banging noise is so loud that the boiler itself shakes with it!

So it is definetely an issue with water circulation.

But what is it?

What can create such a massive noise and shake?

Air and boiling water.

You have a just need to find it.
Thanks, I know the air vent.

Opened it - no water! Switched the boiler on momentarily - air!

Tried it a couple of times but its very time consuming as its a pin-hole vent.

So now I know a definite fault, although I'm still not sure why it causes such a massive banging noise and shakes the boiler!

Next question is how do I bleed the system without powering up the boiler?

One thought is directly feeding power to the water pump?

Another thought - cut the pin-head vent, fix a stop cock, hook up a hose pipe and force water in through that?
The thought has crossed my mind that it could be a blocked feed pipe.

The tank may be full of water but it may be blocked just before it joins the system. Once water has evaporated through the vent it could be that the system is not getting filled back up.

Trace the pipe down from the F&E tank and put a magnet up against it. If the magnet sticks then you know it shouldn't and this pipe will probably be blocked.

Applying mains pressure water to the vent pipe sometimes clears it for me but more often I have to replace the section of pipe.
Try draining a radiator and see if the small tank in the loft starts to fill, I think the cold feed maybe blocked.

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