I've just bought a very old house with a oil boiler that must be over 10 years old. Many of the radiators don't work even though the thermostat is on and valve is open. I've tried to bleed them nearly every day for the last few weeks but I constantly hear air in them gurgling about. It seems like the main pipe up from the boiler makes a lot if noise so I don't know if the old boiler is adding to it. What should I do?
