I have a 3-zone system. The zone on the first floor only has heat on 1/2 of the first baseboard in the zone. The return pipe at the boiler from that zone is stone cold. I have bled out all the air but the water almost seems blocked in the first zone baseboard.Bad circulator pump? Since the other two zones are fine I'm guess it's not a common part like the expansion tank.Any ideas?
It seems from what you say, that there is a bad air lock in the return pipe that cannot be vented. I suggest that you slightly loosen the connection of the return pipe on the boiler, as this is the only way the air in it can be removed. But be ready for water escaping with the air. Do this with the boiler switched off.
check water pressure, should be 12 lbs minimum. if not add some. if the zone valve is open water should flow through.
