Upstairs radiators not heating up

[Davidsian]

3 out of my 4 top floor radiators refuse to heat up. The one that does work is immediately above the boiler and I suspect may be on a different flow. It is an open system.

The radiators will bleed so that water comes out of them. Occasionally there is some heat gets to the intake pipe but rarely goes much further. They used to work fine, but haven't worked properly since I started trying to use them again as the weather has got colder.

I've read elsewhere in this site that this can be caused by stuck gravity check valves. If this is the case, what does one of these look like and what should I do about it?

Grateful for any advice.

 

[chr15]

Do the radiators on the ground floor heat up? if so turn all the ones that do heat up off at one side of the radiator and leave the problem ones open,even if you do them one at a time. You may find that the pump will pump to the rads that don't work and if so open up the rest of them one by one and they may stay on....if yer lucky ,if you get no joy,get an expert in.

 

[shaunyab]

Have you got TRVs on the rads which are not working? if so this could be the problem.

 

[Davidsian]

I've tried turning the others off as recommended above but with no joy.

Yes I do have TVRs on 2 of the 3 - but I've checked they're not sticking in - in fact I've removed them both so the valve should be fully open.

Any other ideas?