Noisy Heating System

[Pacman]

When I bought my house two years ago I noticed the hot water cylinder was leaking so I replaced it and a new immersion. Last christmas day '03' the boiler flicked on at 7 like it always did, let out an almighty banging and crashing and cut out. Turned out to be the pump which I replaced with a nice new grundfos and new valves either side.

After that my Thorn Apollo boiler started hissing like there was a back up of pressure which I put down to kettling and added some fernox noise reducer which worked fine.

The boiler is on low as it sounds worse on high.

Now 7 months later I get clicking hissing and popping noises from the boiler and just before the thermostat cuts it out starts roaring. I have searched this forum and have made sure the pump is bled and is the right way round and the prop spins all the time. I have bled all the rads and checked all joints, I added some more noise reducer today but that seems to have made it worse.

I have had to turn it off it sounds awful

If its simply a build up of scale what would flush it out properly, my corgi gas engineer says the flame is nice and blue and its a shame you can't get the heat exchangers anymore as it works fine.

I've heard you can turn the boiler down but I don't know how

Any suggestions

Please

 

[Pacman]

Incidently I'm sure (I will check tommorow) that the header tank is always filling itself up whenever the boiler is on, I can hear the water filling the tank up, could this be a leak which would require the system to fill up often.

I seem to have clear water in my rads all the time as well if that helps