central heating system help

[rumbumbaccy]

Hi
Had some problems with the heating system, hot rads upstairs, cold downstairs, tried balancing system which worked for a while then same problems occured. BG said there was a blockage somewhere and have now had the system powerflushed( not by BG).
Once again the system heated the house but has now repeated the original problem, except that this time most of the downstairs only get lukewarm and an add-on is stone cold.
Both plumbers have said that the boiler is fine.
Have tried most suggestions in the heating FAQs but the problem still persists.

Any other suggestions would be gratefully accepted.

 

[dcawkwell]

I would suggest you have a blockage personally powerflushing is usually
a waste of money done by people who haven't a clue and do it badly.

Shutdown all the radiators and open up both valves of the radiator
nearest the boiler. Run the system the radiator should get nice and hot.
This should proved the boiler.
Allow system to cool down and repeat the above but open up the next radiator along in the system.

Your symptoms might suggest a failing pump.

If going from radiator to radiator doesn't suggest a blockage at a specific
point I would suggest flushing the system through with mains pressure.