As long as you checked the correct inlet valve, the one on the flexible metal braid pipe, I assume all radiators get hot. Could be system has no space to expand, which is what the expansion vessel is for, If that is full of water, system has no buffer space, Water cannot be compressed, that is why pressure goes up when hot. with air in expansion vessle, air can compress, so buffers the expansion of water. You would have to drain the boiler fully, Not the system, just the boiler, make sure that the expansion vessle empties, slight tap, hollow sound, dull means still full, usually an air valve on top, open, until empty, close valve. refill boiler to pressure, reconnect to rest of system. Try that. As it has just started should not be system design, I fitted an extra vessle in my system, because of the water, capacity, But not usually needed. You should not need to bleed a radiator, the system will have a 3bar over pressure release valve, problem when they open is sometimes they do not close fully and you get them leaking, manually open close a few times usually sorts it, if not it would need replacing, But do not worry about that for now.
SD, January 2012
