Boiler still whistling

[Matthall788]

Hi, my central heating system is still whistling. Have tried ferneaux f3 followed by f2. The f3 seemed to help but the noise has returned since putting the f2 noise silencer in. Any suggestions on what I could try next? Thanks

 

[Matthall788]

Also, should I have flushed the system again after using the f2?
And some of the radiators won't heat up. Not sure whether the symptoms are linked

 

[muggles]

When did it start whistling? Any obvious cause? Have you started a new post half way through an existing topic?

 

[Matthall788]

Hi Muggles, it's been whistling a couple of years now but normally only gets bad half way through winter. This year I've been tasked with getting it sorted. It's only the central heating, not the hot water so is tolerable most of the time.
I've bled the radiators to mixed effect previously but can't get any more air out atm

 

[muggles]

What boiler make/model is it?

 

[Matthall788]

Glow-worm fuel saver mk2