how to get heat in one radiator?

From the mis typing, I assume that you get hot water into a radiator, but only cold if you bleed it. You will. Until the water has had time to circulate, check the outlet valve is open. IF you have thermostatic valve on the other radiators, you could turn them off, so that only one on is the problem one, the flow would then have to be through that. if still cold, outlet valve faulty, or blockage(not very likely, but possible)

SD
December 2011