NO central heating or hot water

[josek]

This is an old system and a leaking pipe was fixed a few days ago.

central heating system was refilled and all radiators have no air in them.

The pump that operates the system (grundfos selectric 15-50) made a horrible noise which was made quieter by adjusting the white disc on the top.

I thought pump had packed up but day after it started up making the same horrible noise.

Has my pump had it and what function does the white disc on top of pump have?

 

[ecowarm]

sounds like air in the system, the white disc is speed control you have probably turned it down or between speeds so not turning at all.
If you run the pump with air in it it wont last long.
I suggest you get a plumber/ heating eng to look at it