do you only have to do this once a year? If you do, it doesnt sound like too much of a problem. If you had a leak you would need to bleed the rads more often.Every year at this time, when I begin to turn on the oil-fired central heating, I find I have to drain one or sometimes two radiators. Is this normal?
Should you bleed a rad when they are hot or cold?
When cold, there is no pressure so the air wont be forced out.