I have 1 cold radiator downstairs and 1 upstairs but all the others are fine. I have bleed the radiators but there doesn't seem to be an airblock as water comes out . any ideas?
Hmmm, is it cold all over? If not, it might be corrosion/rust/magnetite slowing it up. Close both valves, disconnect and flush out.
Rad valve issues - prob not if bleeding ok, but still a possibility - partic if you have TRV control. They tend to fail faster than the good old wheel valves.
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