Radiator problems, please help

[Paula laws]

Hi everyone please could you help me work out what's wrong with my Central heating, my radiators were cold at the bottom so I had them flushed through, since then the heating engineer got them all lovely and hot, but after being off for the night only the upstairs ones were working ??? He came back again to balance them, same again, after being off for the night no heat downstairs, he flushed them through again which didn't help so then we discussed that the pump ( which does humm quite loudly) probably needs replacing, we are now waiting for him to come back to fit the new pump, but strangely today the heating kicked in and is now working downstairs ????? Except the last one which is the downstairs bathroom that is stone cold. Does this sound like they pump?? Also the boiler is making bubbling noises.
Thanks

 

[Deleted member 120897]

Sounds likely to be the pump and possibly would have checked this before a flush, unless there was evidence that a flush was needed.