Tapping baseboard radiators

Hi, my house is heated by an oil fired boiler via baseboard radiators. It's 2 floors and 1 zone. All radiators on 1st floor pull heat. Second floor radiators pull heat EXCEPT for a loop of 3 in a corner of the house.

The basic issue is I can get air and cold water from 2 of these. The remaining one I get nothing.
Adding to this is the other 2 will drip water then stop. Until the the boiler/circular pump comes back on.

To me this sounds like a physical blockage with trapped air. Does this sound weird? Or is it just a LOT of air trapped?

On one of the 2nd floor radiators I have an auto air-vent (Honeywell FV147) and I did hear this hiss then stop sometimes when the system comes on. I figure this is normal....purging air then stopping as water pressure closes the valve.

Any suggestions, opinions.

Thanks.

Sounds like the water pressure is low. May have a bad auto-feed. On a two-story house it should be between 12 & 15 #

The pressure gauge reads in the 12 -15 lbs range.

And it's only one area of the 2nd floor. The rest of the radiators up there are heating fine and bleed easily. All of the radiators giving heat on the 2nd floor are individually loop branches from the main feeds. The problem radiators seem to be serial connected and I'm not sure where the feed and returns are connected. But all have their own bleeders valves.

johnjh2o said:

Sounds like the water pressure is low. May have a bad auto-feed. On a two-story house it should be between 12 & 15 #

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