Noisey boiler

I've read all the previous posts. I can't find anything similar, but apologise if this has been asked before!

Our Vokera combi boiler has started grumbling since its been turned back on for the winter. When the heating has been on for a short while it can start to hum. You can stop it humming by turning on one of the hot water taps. But sometimes if it has been quiet it will start to hum after you have been running the hot water. If this is the case the heating has to be turned off and back on after a few minutes.

It used to do it occasionally earlier in the year if the pressure was too high or too low (I can’t remember which), but now it’s most times the heating is on. Other than this the boiler is faultless, but its starting to get annoying. Anybody got any ideas?

Is it the same type of sound as when a kettle is "singing" as it heats up? If so you could try adding some Kamco (usual disclaimer) System Hush liquid to the system (or some thing similar) and see if it helps.

Oilman, You could describe it like that. The system hush you talk about, where can you get it from? If its not expensive it may be worth a go!

x200 is also pretty good stuff for this, you can get this from any good plumbers merchant (about £16) and i think fernox do something similar too but i havent tried that one.

AL

Just an update: I've not done anything about the boiler yet because I want to move a couple of radiators in the next couple of months so I will be draining down and re-filling a couple of times so will use the cleaner that people have suggested above. But now the boiler seems to be quiet until you turn on the hot tap with the heating on. Then it grumbless and you get the long drawn out 'moan'. Sometimes it will stop on its own or you have to turn the tap on again or sometimes the only way to sut it up is to turn of the heating. Do people think that is still the same problem?