We had a new combi boiler fitted a couple of weeks ago, but before that we had one radiator that hadn't worked for awhile. anyway we picked a rubbish plumber who advised the radiator was old and needed replacing as he had only allowed one day for the job he hadn't priced to replace any radiators. So after heating system was changed every radiator now works brilliantly except for one bedroom.(Same radiator that has not worked in ages) We have replaced the radiator and put new valves on, sometimes one pipe gets hot and other times it doesn't but radiator is always cold. (Freezing in every section) We have tried turning all radiators except the cold one off then turning the central hearing on. We have bled and re bled all the radiators. We have even removed to pipes to the manifold to check water was traveling through. All have not worked. We are now at a loss as what to try next, really don't want to get another plumber and we have no luck with them at all. Anyone help me please?