Bleeding central heating pump

[ScurvyPete13]

Can anyone help?
A week ago I put Fernox F3 cleaner in my system because it was really noisy. I then emptied and flushed out the system a couple of times. I've done the final filling including Fernox inhibitor.
It now sounds like there's a load of air moving through the pump. I've bled all the radiators a bunch of times and there's no more air to come out of them.
I read the FAQ about bleeding the pump and had a go, making sure I set the valve to manual and the pump was off. When I undid the screw in the middle of the pump nothing came out. No water, no air, no nothing.
Am I doing something wrong? Have I missed something?
Are there any other suggestions?

 

[Baxmax]

No need to swear !

 

[MrGassafe]

Vent the pump with the system running.

 

[ScurvyPete13]

Mr Gassafe: really?
Everything I've read says to turn the pump off.
I'll give it a go tho.
Thankyou

 

[dcds4]

Mr Gassafe: really?
Everything I've read says to turn the pump off.
I'll give it a go tho.
Thankyou

yes really

 

[ScurvyPete13]

OK, I tried that and maybe I was impatient but still didn't get anything out.
I'm sure there might be some other reason for my heating sounding like it's going to take off so if there's any other suggestions I'd love to hear them.
It does honestly sound like there's a load of air moving around but I don't know how to get rid of it.

 

[muggles]

Maybe your pump isn't working at all, are you sure it's spinning?

 

[ScurvyPete13]

Pump seems to be running. It's vibrating and carries on going for a bit after the boiler stops, like it's sposed to.
Do I need to be a bit more patient with bleeding the pump? Is it supposed to do the same thing as when you bleed a radiator?

 

[xr4x4]

what happens when you remove the sliver disc completely? can you turn the pump inside manually when off?