Air in central heating pipes

[Mick517]

Hi i live in a bungalow The problem is air in the system my central heating has had an air lock for years 3 out of 7 rads are cold.
i have bled the rads, drained the system and slowly refilled them bled again, still the same.
this time i am draining the system and filling from the lowest point which is drain off close to the floor.
Hoping the water will push air up and out.

What do you think i will open a drain off valve in the loft to let air out.
Have tried everything i know
Any help please
its not a combi boiler

Thanks Mick

 

[terryplumb]

I doubt the 3 radiators that don't heat are due to an air lock. If you close off every radiator except one of the 3 that does not heat,by their thermostatic radiator valve
( TRV) ,or wheel head if no TRv, and run heating system ,see if the cold rad now heats up.

 

[Mick517]

Hi thank you for your reply terryplumb i drained the system down and refilled slowly backwards bottom to top. added inhibitor almost last thing.
Restarted everything took a bit to settle down balanced the valves best i could red hot rads all but small bathroom rad which i hope will sort itself out .
you can still hear air trickling down the pipe when heating is turned on. soon as it stops heating starts up.
if water and heating on together heating stops and rads start to go cold. turning water off and you hear air in pipes when air has gone heating restarts.???
very funny???
just dont know where the air comes from but all working ok for now
thanks for your reply very help full
Mick