This is issue I been working with on another fourmn I need all the input I can get so i'm looking outside my normal routes. Here it goes ORIGINAL QUESTION/ISSUE I am trying to help a old couple who is family friend get heat back on and saving them from these enormous electric bills. I am a contractor/handyman by trade so I know different skills. Starting out I had to rewire the thermostat because guy totally messed it up where blower wouldnt' work, got that fixed, but wouldnt' blow hot air. So went to bleed system, Its a one pipe system with 2 shutoff valves from what I can tell. Radiator is in the ceiling(hard to reach access) with a huge central boiler on outside that provides both heat and airconditioning. When starting to bleed noticed that the top bleeder was broken(tooth chipped) I had to drill out and replace with new bleeder valves(BOY WAS THAT FUN ) I finally got it completed and started draining the system, got all air out as I can tell. Only thing I wish I would have done is since it was tight space(trying to avoid tearing drywall if don't have to) is I had to cut copper pipe to stop flow of water because water/evaporation kept interfering with soldering process. I Wish I would have while it was cut to purged the main water supply, attaching compression coupling attached to garden hose and clearing pipes(just because). Before all the process of soldering the bleeders alot of debris had been cleaned out(black-about (5) 5 gallon buckets of muck water). After soldering the bleeders on and just like purging the main valves I wish I could also have purged the radiator to by the same process except instead of draining, connecting to water supply and flushing it out. I was in hurry and it was getting late and well most of you can understand being rushed. I totally forgot, and when bleeding I noticed more gunk was coming out, not sure if it was much but it was black as I decidedly(after fact) to lightly tap the supply valves and that loosened more . both water supplys are hot UNTIL I turn on the blower, then one pipe stays hot(assuming this is the supply-pipe to lower bleeder) and the other pipe cools of rather quickly(assuming return-pipe to upper bleeder) I know enough to figure it out EVENTUALLY but dont' do it everyday so I'm not efficient at it. Never messed with hydronic system mostly just forced air, but assuming how it works is hot water is introduced, blower blows hot water, then the cooled pipe is the return that connects back to the boiler then gets reheated???? . Does this work by constantly moving hot water? if it does you would think that the pipe wouldnt' get so cool, but then again I dont' know how long of coil it is. I know a car radiator works by a thermostat, would this system have a thermostat? mind you its about 30 years old, rusted and more likely original. I been reading about trv valves and such but doubt this has anything like that. Again its a ceiling radiator with 1 central boiler feeding MANY condos, cant see coils or feel them to see if has cold spots. I am trying to save work if I dont' have to remove the drywall, but will If I have to. Looking for ideas before I start doing something that I really dont' need to. I'm thinking of unsoldering the system and starting over purging it, If I do any ideas on a flush chemical? I heard that acids will breakdown pipes, could cause leakage in other areas and could cause clogging faster in future. If theres a safer alternative/or homemade brew? maybe baking soda? I dont' know but If I don't have to I really REALLY dont' want to have to unsolder let alone remove the ceiling. Any Ideas and ideas woudl be GREATLY APPRECIATED!!!!!! NEW UPDATED INFO the person I changed out valve out for called me yesterday.. seems to be heat is working fine now...the problem GET THIS! THE THERMOSTAT!! what? no way in hell is the thermostat the problem, I am not a professional by any means in the HVAC trade but i'm also not stupid. The thermostat in this situation turns on and off the fan..thats it.. I mean there is 2 wires, just like a switch, when connected the blower comes on. Right??? I mean thats what happened when I connected the two together. Please all professionals write me back and let me know if this was incompetence on my part. I did change bleeders, I bled system, I found out they use black dye in system, which comes clear after while from what the maintainance guy said. I also found out they had the maintainance of complex come over checked over everything, had company called Oasis come out and they was going to bleed system with a "special pump" but coudn't because of bleeders? You would think that if it was the "thermostat" that these people would have pointed that out....correct. My guess is this, when pumping out and bleeding the system, I left the blower on all night, over time it must have loosened up the system. Before leaving I also lightly tapped the supply valves and piping, including the radiator of what I could access.. So this seem logical or am I kidding myself? I"m just 1. trying to convince myself that it wasnt' that simple 2. was to show them that my work was justified, I am getting paid for my time, but I have to know it was well deserved.