BM II pouring noise

Hi,

Whenever my boiler (Potterton Suprima) fires there is a loud sound of water pouring in the BM II.
After a bit of research, mainly on this forum, i believe this to be because the water level in the BMII is below the pipe returing from the boiler.
My F&E tank is full, so this points to a blocked cold feed from F&E to BMII, right?

So, to try and solve this, i fed some cable down the cold feed expecting it to get no further than a couple of inches. However, it seems to go in about 1ft before hitting something.

How far does the cold feed pipe carry on into the BMII? is there a float at the end of at similar to the float in the F&E?

Any help/advice appreciated.

Cheers,
Matthew

Depending on the unit can be 5 to 7 feet.
It goes down and then round like a shepherds crook.
If not re route a cold feed into the drain off.
But try to clear the blockage.
Mike