2 Cold rads on a system with 8 hot rads

[NODDYNODSVILLE]

Evening all.
I have open vented C/H system with a heat only boiler and 10 rads over 3 floors.
I have just replaced a rad on the middle floor. Drained system down for new gateway valve for cold feed for header tank. Refilled system no leaks, 👍, but the top top 2 rads won’t get hot.
ALL rads contain water, I have bled all rads. No hot water getting to flow pipe of either rad on top floor.
All other rads are working.
When I bleed the top cold rads, all I get is cold water.
Any ideas or help in helping me would be much appreciated
Simon

 

[SimonG]

Shut off the 8 hot rads completely. It will be an airlock.

 

[NODDYNODSVILLE]

Shut off the 8 hot rads completely. It will be an airlock.

I have drained system down 3 times over last few weeks, and still these 2 rads at top of house don’t get hot. Cold water comes out of both bleed valves. I will try shutting both valves on other 8 hot rads..
[automerge]1602000407[/automerge]

Shut off the 8 hot rads completely. It will be an airlock.

Thanks for that tip. Worked first time . Now what. Do I follow Dotty’s advice on the forum Jan 2016 how to balance the rads..?