"The Natural Philosopher" wrote in message
...
jason hunter wrote:

Hi, hope someone can help,my girls heating will work upstairs but not
down.These guys have been and all have suggested the pump and some
have replaced it.One has replaced the zone valve,all have suggested
and then dismissed blockage as water does come out of the drain
point.Its quite an old boiler which seems to fire up fine and rads do
get hot.Im sure that when I used Fernox it did help and tried to
balance the rads.Any guidance what I can check to do an in depth
diagnosis and info on balancing properly.The boiler is a wall mounted
type not combi.I can get more system info tomorrow .Thanks Jason

Almost certainly an airlock.

Try over speed on the pump

Try reversing the pump and run for 15 minutes. Then turn it back around.