More cold radiator problems

[gatman]

Hi

I took off a downstairs radiator to do some decorating. While this has been disconnected some of the other downstairs rads haven't been getting even warm. I have put the rad back on now, having cleaned it out, and am still having problems.

When I put the heating on the upstairs rads all got hot, too hot to hold your hand against for more than a couple of seconds. All but one of the downstairs rads stayed cold but the other got hot as per the upstairs. I have bled all rads in the house and bled the pump with no avail. The 3 way valve is working and I have hot water.

I tried turning off all the upstairs radiators but the downstairs problem continued for a while. Some of them then started to get tepid-warmish and some stayed cold. I have now turned off all the rads in the house except one. This has now got hot but I can still hold my hand against it comfortably. The thermostat is set to 30c and the pump is set to 3. The boiler cut in to warm the rad but has now gone off again but then cuts in sometime later. The house is no where near 30c more like 12c ish.

I've read through a few years posts and I think I've tried most of the solutions with no success as yet. I am presuming it may be sludge rather than a pump problem. The rads that only get warm at best appear to be consecutive if that helps.

I'd appreciate any help.

Thanks

 

[MANDATE]

Just wondering if you drained the system for any reason.
Removing a radiator does not create a problem.
I'm thinking along the lines of a 'air lock' if the system was drained,
If you think sludge, then you might want to try this:
Bleed cold radiator with one rad valve (a) closed and valve (b) open. then again in reverse order.
If it does not bleed in one of the two cases, then yes I would think sludge.
whereas a air lock would have no adverse effect.
It would have been wise to run off a bucket of water from each valve before fitting radiator.
I have a 5ft length of clear plastic pipe with fittings at each end to fit to valves before fitting radiator, (only used once after removing the offending radiator).
With both ends connected, valves opened, CH on could see no flow!
Close one valve and dis connect from valve, run off water using opposite valve and then again in reverse order.
This removed lots of air and then re connect and flow of water could be seen in tube. Re fit radiator. Problem solved. This method is cheap, effective and may help get rid of sludge