We've just moved 2 radiators downstairs and they are working fine but the upstairs ones have become cold at the top. We have tried bleeding them and have got out quite a bit of air (which smells funny - is that normal) but they are still only warm at the bottom. we have a Worcestet combi boiler but didn't drain the system when we moved the radiators. Do you think it's an airlock? any ideas? Thanks