Boiler making chugging noise

[Terry34673]

My Vailiant Ecotec Plus boiler sometimes starts making a very loud chugging noise, it doesn't sound healthy. Pressing the pilot light restart button seems to resolve the problem temporarily. Recently this has started happening every time it has been on for a few hours. Please see this youtube video for an example. If you listen with sound you should be able to hear the noise :

What is causing this and how can I fix it? It serves a two up two down house and 1 bathroom / hot water.

Any help would be hugely appreciated,

Thanks in advance.

 

[Madrab]

Terry, you need to make the video open to all, it's asking for a sign in before viewing

 

[Terry34673]

Ah, sorry, should work now.