No hot water heat upstairs after fixing pipes

[maarass]

Hello, I had to replace a small section of copper piping in an upstairs bedroom. We were pulling out the carpet and where it was under the registers knocked loose a fitting. So we turn off the water to the heating system, and drained some out the valve by the furnace so we could solder. This is a (summer/winter) system, it is a oil furnace with a expansion tank which heats the system. There is no hot water heater. So we soldered in the new fitting and turned on the water. No upstairs heat (3rd level). The main floor and second level (split house) worked fine. So we bled the line till all the air came out and did the same to the expansion tank (but only a little). Still no heat upstairs. All the other baseboards are crackling as usual. I cannot find another air - release valve or anything like it. Does anyone have any simple suggestions to try before I call in the pros ? thank you.

[roger g]

What pressure (water) do you have in the system? It's been awhile but the more floors you have (in height) the higher pressure you must have in the system. I'm thinkingit;s around 8 pounds per floor so your pressure should be over 20. Double check on that though.
I used to put in lots of shut off valves so I could isolate each zone. I would put a drain cock down near the bouler with a shut off valve just downstream of it. I would close off ech zone and the shut off near the drain cock and then open the drain cock. I would fill eack system separately and wait for all the air to come out the drain cock then close that zone and open another zone and fill that.
Dammit I'm not sure I can follow what I just sain. Either way I'm sure it's some thing really simple like an air lock or a water logged expansion tank.

roger

[maarass]

Thanks for the reply. I will look for a pressure guage.

[maarass]

The contractor came over and purged the system. I now know I have a mono-loop or mone something syste. where lines come off of tees so it's NOT one big loop. We left it on for a while and cranked up the pressure to see if it would takee care of itself. Not so much pressure that it would burst the fittings. So no luck. He says they will have to put in a valve past the air bubble to release it. Question: If I were to put a brass self tapping valve like for a ice maker past the clog, would that do the trick ? Thanks