Radiators not warming up!

[Nige]

I recently changed two wheelhead valves on two rads in a small flat. It has one rad at the bottom of the stairs, and four upstairs in the living area. It is heated by a back boiler, has a hot water cylinder, tanks in the loft space above etc. It took a while to drain the system down (the water was clean), and to bleed.
With all the wheelheads and lockshields fully open, only two of the upstairs rads are getting hot at the top, no warmth at all in the others and the pipes to the downstairs rad stone cold.
The room stat is turned up to max which must exceed actual room temp, the pump is on speed setting 3.
Any thoughts would be greatly appreciated, this is the first time I've worked with a back boiler, wonder if I'm missing something really obvious, or if its just a stubborn air lock!!

shut all the rads and open the lowest one till it gets hot.
then try another rad till it gets hot etc.
sounds like a airlock in system.
if this fails could be sludged up and would need to know more about the system

[Pendle Plumber]

I think it needs balancing as ajs heating said may be sludged up in which case powerflush may be needed.

[Nige]

Thanks v much for that. Will give it a go.

[ViSaGe]

could be the pump, try it on no.3 see if that helps.

>The room stat is turned up to max which must exceed actual room temp, the pump is on speed setting 3.

if you read the post again you will find it's on 3.

[ViSaGe]

my speed Reading failing me again try reversing the pump to see it that helps.