Noise from pump and boiler will not start

[sipeki]

No Hot water and CH.
Boiler will not switch on.
Noise coming from pump, I think. Noise sounds like it is coming from heating system overflow tank. I think this is due to the sound being transmitted from the pump, along the pipe.
Switching boiler off then on, does not start the gas boiler. No pilot light. Switching electricity off stops the noise. So timer is ok.
How can do I know that there is water getting to the pump? As the noise could be because the pump is dry.
Everything was working fine this morning. No sure when the system stopped work.

 

[twgas]

check that there is water in header tank

 

[sipeki]

If the head tank is the small overflow tank above the boiler then there is water in tank. I can see that the water is above the pipe at the bottom of the tank. Pressing down on the "ball" valve , more water enters the tank. So there is water getting to the head tank.

When I turn the electricity off to the heating system the noise stops, as the pump stops. When I turn back on I can hear water noises, and the noise of the from the pump starts again. This noise is not usual. The pump motor housing is hot to the touch, very hot but not too hot that I can not lay my hand on the casing.

 

[twgas]

have you opened the bleed screw on the pump and bled any high points near the pump?

 

[sipeki]

What is the bleed screw and what is bleeding the high points? I am not familiar with CH systems?

 

[sipeki]

I take it that this is a simliar process to bleeding radiators of air. On the pump there is a screw the size of ten pence, is this the bled screw?