Apollo 30/50b noisy on high thermostat

[mturbo23]

Hi I have an old Apollo 30/50b boiler that has worked ok for a while however recently when it is switched to the high thermostat it is making lots of strange noises. It is making fizzing sounds and generally being noisy with occasional loud bangs which it didnt before.

I have already changed the pump, mid position valve cleaned the system with Fernox and cleaned out all the radiators (which didnt have too much black sludge in). The system is gravity fed and 8mm microbore.

The boiler runs ok on the low thermostat apart from being a bit noisy when cold. The hot water and radiators all work as they should but we will want it on high at some point over the winter!

I have been told to try cleaning the system again as it could be crud that is stuck in the boiler but im not sure if this will fix it.

Does anyone else have any suggestions? It seems to me like the problem is with crud in the heat exchanger not the rest of the system. Can the heat exchanger be cleaned?

Thanks...

 

[ianmcd]

you have one of the oldest boilers that it has been my honour to keep going but sadly mate its time to change the old fella and put him to rest, you can spend money and keep it going but I wouldnt , you will need a few system upgrades too for your new installation , good luck

 

[Dan Robinson]

We have hundreds of these on a development - on SE duct flues so it is imperative we kept them going as long as possible.

All of them however are perfectly happy on the low setting.

Get a MagnaClean.

Dose the system with some Sentinel X200. Let the boiler live on for a few years whilst you save for a GOOD upgrade.

 

[mturbo23]

Sadly I thought that could be the case. I take it powerflushing would not do the trick as it appears the problem is in the boiler. Could the part be taken out of the boiler and cleaned seperate to the rest of the system?

Will try and get some cleaner to add to the system in the meantime

 

[dcawkwell]

A flushing through should help with some cleaner.

Pump could also be failing a new pump might be needed.

Perhaps the thermostat is also faulty.