Hello, first timer to the forum.

My system is a Triangle Tube HE, put in 15 months ago, two zone system.

I live in MN, so it's damn cold. I noticed one of the upstairs radiators wasn't getting heat. I attempted to bleed, however all that produced was a short fizzle of air. I attempted bleeding the remaining radiators upstairs, each had some air to give, but not much. The system I have is supposed to remove air in the lines which it appears it failed to do so. The flow upstairs is good, 3 of 4 radiators are getting heat, etc. except the radiator furthest from the boiler which is my cold radiator.

In reading the forum I attempted to turn off the valves to all other radiators and attempt to force the radiator to take heat. That did not make a difference. I did notice in the basement where the boiler sits, at the manifold where the outtake hose is connected, it's not getting heat where all other hoses on the manifold are. I attempted to turn off the flow to the cold radiator and adjust the flow by turning the knobs, still no change.

This boiler was working fine a few weeks ago, I fear a sudden drop in the weather (no heat in open basement either) caused an issue.

Any suggestions or advice as to what else to try would be much appreciated. I dread dropping another $450 as they were just out for another problem (replacing a valve on another radiator)