Bleeding radiators

Hiya all,

I have a weird problem with my radiators.

They are producing a lot of Hydrogen (but not surprised at this as we are removing radiators, cleaning and replacing due to decorating the house), but when i bleed a radiator (usually the first one I bleed) the radiator drains fully of water, then refills (after a lot of gurgling), rather than just filling up as I would expect.

Anyone have any ideas as to why this should happen? it has never happened on any other system i have dealt with.

Thanks

Taff

System is a back boiler on a gas fire, connected via a pump to the radiator system. It's not a nice system having been put in back in the 60/70's after the house was built and has at least 3 legs rather than a full circuit.
The header tank is correctly fitted (I think, i replaced it a month back and just checked it today) with the water level about 10 cm high.

Sludge build up methinks foothsooth

do a search on "flushing"

Thanks, will live with it for a while, have 2 rads to put back on and then will give the whole system a good clean out.

Thanks again

Taff