Radiator not working question

I'm a little stumped with a problem I'm having with our heating.
All the radiators except one gets hot (hot, not just warm). The radiator valve is open, and I've tried various positions of the lockshield valve (from closed to half open to fully open) with no effect. The radiator is an old one (well, not new at least! Same age as the rest of them) and is a very long double one (about 7+ foot long?) - all the rest are much shorter ones. I tried bleeding the radiator and found that it didn't need it. This radiator gets slightly warm (as in doesn't feel cold - but it doesn't feel remotely warm if you see what I mean).
I've tried turning the pump up from 1 to 3 and it did make it marginally slightly warmer, but still nothing high enough to warm the room - I'd still call it cold.
The radiator inlet (with the adjustable valve) is hot (hot as the rest of the radiators around the house) but the radiator side of the valve doesn't feel any hotter than it might be through conduction of heat from the pipe. The radiator outlet (with the lockshield) is cold (or as cold as the radiator).
The possibilities I've thought of are these:
1.) Radiator valve is blocked/stuck - the valve feels like its opening normally (it screws up and down) but something is stopping the water flowing into the radiator. This fits in with the inlet pipe being hot, but the radiator just past the valve not being hot. 2.) Radiator is full of sludge - though I'm not sure about this as it would have to be on both front/back parts - which seems strange.
Any suggestions?
I'm planning on putting TRVs onto most radiators sometime and I'd like to also flush through the radiators at this point - but I don't want to have to do this immediately.
Thanks
D
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an
very
ones.
still
flowing
would
to
I had a similar problem, although the pipes to and from the rad were also cold. I took the rad off, when I opened the TRV-valve end there was a lot of sputtering, I guess an air-lock in the pipes somewhere. When water flowed properly I put the rad back on, now all is OK.
NB Plan B was to Vax out the pipes (I assumed there was a blockage somewhere)
NB2 The rad needed flushing ten times to get rid of the crud.
Pete
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Hi David,
Try closing every other radiator off and turning the pump up full. Once it gets hot then you may be able to open all the other rads and it may keep working fine. If you open all the other rads and this one then goes cold, the system may need balancing.
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radiator
Turned off all the other radiators (bar one) and turned the pump up full. Large radiator got nice and toasty. Opened up the other radiators and then the other radiator in the living room didn't get hot, nor the one in the hallway, and neither did the large one I'd previously got hot! Closed off the large one and the hallway one then got hot again, but the smaller living room one still didn't get noticably hot. Turned on the gas fire to keep us warm this evening.
I think you may be right about the balancing. I assume that all I need for that is some kind of themometer to measure the input/output temps and adjust the lockshield to set a certain temp drop over the radiator? Is that correct?
So - what sort of thermometer do I need? I've heard of people talking about nice IR ones - but I've yet to see any which are reasonably priced. Would this basic one do: http://www.maplin.co.uk/products/module.asp?moduleno6138 its priced at 15 which I think is the most I'd want to pay for something I'd just use setting up the heating. 10 would be better though!
Thanks
D
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<snip>

for
adjust
about
15
setting
Slightly cheaper than http://www.screwfix.com/app/sfd/cat/pro.jsp?id 755&tsD938.
I have two thermometers which were about 6.50 each from a local plumbing supplier but these are simple dials held against the pipe by springs. Tried to find them in Screwfix and BES but they didn't have them.
Brannan Pipe Thermometer Brannan Thermometers Cleator Moor Cumbria England {cue Google} Main benefit is that they can be clamped against the in and out pipes and just left there while you adjust things.
HTH Dave R
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Would
Tried
Thanks for that - I've now found some at a local place and got some (24.97 I think for the pair after VAT). Still, better than the 15+VAT I'd seen in another place.
Just need to give it a go now.
Thanks
D
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Just in case you haven't seen them, the FAQs offer some help:
http://www.diyfaq.org.uk/plumbing/plumbingpage1.html#balancing
http://www.diyfaq.org.uk/plumbing/rad-balance.html
mike r
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