Downstairs radiators are cool?

[SproutsDad]

I have a sealed system Vaillant ThermoCompact and Ariston unvented indirect cylinder.
I recently changed a downstairs radiator and completely drained the system. It is refilled and running again but there is very little heat downstairs, upstairs all rads are hot or warm.

There was an initial problem with a lot of air in the system which I thought had been bled out via radiators. Current boiler gauge pressure is 1.2 bar. There is no obvious air in downstairs rads or cold sections top/bottom - they are either cool/cold or a couple are slightly warm?

I have balanced upstairs lockshields to a half turn open, the downstairs ones are fully open. There is probably a more scientific fine tune for balancing but I understood that this should send the hot water to the downstairs rads.
Note - the boiler is upstairs, on 1st floor.

I have bled them all today (only a little air in high upstairs towel rads) and opened up all the downstairs lockshields. Note - I bleed rads with system turned off, but the water will sometimes still be warm. Should it be cold/cool?

While writing this thread upstairs, I could hear a couple of fast air surges in a tall column rad, the highest point. Could the opened up lockshields be starting to shift an airlock?
The pump has run quite noisily ever since this initial problem, the auto-vent cap on pump is open, not sure if there are choice of different pump speed settings?

Also - Perhaps it is nothing at all but I notice the 3-way valve lever stays up (but slack) even when auto-switched to heating. This might be normal?

Any ideas please someone, it is starting to get quite cool at night?
Help much appreciated.
Many thanks

 

[TCCHeating]

Youve def got an airlock.

Close all rads and the auto bypass if you have one. Fully open just 1 rad. Run the pump while bleeding the rad and make sure you have just the heating circuit on. Continue doing this on each rad 1 at a time.

I would also keep bleeding the manual vent in the center of the pump as well.

It may take a bit of time to get all the air out but you'll get there eventually.

 

[SproutsDad]

I think it is starting to shift, one rad downstairs has warmed up evenly.for bleeding rads one at a time .....
1 - how do I set it with just heating on, without any water heating I presume?
2 - how do I manually bleed the pump vent, the cap is open all the time?
3 - what /where is the auto bypass? Is that the dam as the 3-way valve?

Thanks

 

[SproutsDad]

Update ...
Some of the air is starting to shift since I opened up the downstairs lockshields to be fully open - is that Ok? Also just a half-turn open on the upstairs ones?
One rad downstairs has warmed up evenly. In order to bleed the rads one at a time, if I do as you suggest...?

Q1 - how do I set the system with just heating on, that is without the hot water heating I presume?
Q2 - how do I manually bleed the pump vent, the cap is open all the time, I assumed it was an auto vent valve on the pump?
Q3 - what /where is the auto bypass? There is a tall black capped valve (?) by the hot water tank with RWC 3.5 bar written on it, is that it?

Thanks for all help​