I recently drained our system to put new valves on the radiators and clean some sludge out of two of the downstairs radiators. I turned the radiators off upstairs emptied the radiators downstairs did the job, now can not get water into the radiators upstairs, tried bleeding them and no air comes out. Also header tank does not drain properly (drained system before with no problems), can anyone help.
Sounds like the cold feed is blocked if the tank did not empty. In most cases the blockage will be at the point the cold feed tee's in next to te expansion tee.