I hope someone can help me. I have a couple of radiators in my house that are not working and its -4c. I have a vailiant boiler. 2 rads work upstairs out of 3. I have bled them all and checked the boiler is at 1.5 bar rating. 1 of the radiators feels moderately warm at the top but cold at the bottom. Down stairs 3 radiators work - one has a small leak (plastic pipe on this one!). However 1 is stone cold. All rads downstairs have been bled for air - no problems here. What is the general opinion relating to the prob. Some people have said I may have an air lock - how do I get rid of this, some have said I may need a new pump. Please help.