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?
Don't think it really matters - but I am open to correction! . You only really notice a cool area on the rad when the heating is on, so I would have done it when the rad is hot.Should you bleed a rad when they are hot or cold?
If you've no pressure when cold, you have bigger problems. You need to open the filling loop while bleeding to allow water in to replace their air, the pressure from the feed (likely a header tank) is all you need. That valve then needs to be shut tight once done.When cold, there is no pressure so the air wont be forced out.