Cold radiator, cold pipes!

[pwo82]

Hope someone can help! All radiators in my flat work perfectly except for one in the living room. It's stone cold as are both pipes leading to each side of the radiator. This is what I've done troubleshooting wise so far.....

1. I've repressurised my combi boiler (showing just over 1.5 now)
2. Bled all radiators
3. Turned off all radiators except the faulty one
4. Checked both valves (TRV and the standard lockshield one) are fully open. The TRV PIN is fine, it presses down about 5mm or so and then springs back up so looks good

I'm at a loss as to what else to try?!

 

[Burnerman]

Even if the faulty rad actually bleeds water, this doesn't meen to say that alls well, as water can enter via the flow or return.
So, either the TRV or lockshield is faulty, or there's a blockage somewhere.
Running a magnet around the visible pipe runs may help - if there's an attraction then there's magnetite too.
John

 

[pwo82]

So even if the pipes that lead to the TRV and lockshield are stone cold it could still mean that either valve is actually at fault? Or is it more likely a blockage?

If it's a blockage then it sounds like I'll have to get a plumber in as I have no idea even where to start myself!

 

[PlumbGas]

So even if the pipes that lead to the TRV and lockshield are stone cold it could still mean that either valve is actually at fault? Or is it more likely a blockage?

If it's a blockage then it sounds like I'll have to get a plumber in as I have no idea even where to start myself!

If either valve isn't open then no water flow = no hot water can get to pipes or Rad, take off TRV head and see if the pin under it moves up and down, you may need someting hard to try it though like a flat piece of metal (knife)

 

[Burnerman]

Yep, if either valve is stuck shut, then no flow.
Things to try......is the lockshield valve actually turning with the knob? Sometimes the plastic splines strip, giving this illusion.
You seem to be familiar with the TRV - if the pin comes up, then thats usually fine.
This is what a plumber would do.....
Turn off the lockshield fully
Remove the TRV top, and use the decorators cap supplied with it to shut the valve completely (Even with the TRV indicating OFF it can still pass some water).
Disconnect the radiator from the valves, catching the water in a shallow tray. (If the water is black, then its a sure sign of magnetite).
Open each valve in turn....hopefully the dirt will shift (the system will naturally depressurise if it does) and run the water until its clear.
Reconnect to the rad, allow it to bleed and repressurise the system.
Hope this helps a bit!
John

 

[pwo82]

I removed the plastic cover from the lockshield valve and opened it fully with an adjustable spanner and I'm 99% sure the TRV valve is fine so it sounds like I'll have to try what you suggest and remove the radiator. Thanks for your help, I'll see how I get on!

 

[Burnerman]

Please don't forget about the decorators cap tip.....
Support the rising pipes to the rad valve as you get busy with the spannering - don't let them twist.
John

 

[pwo82]

Thanks for the tip, I don't actually have one spare so am off to B&Q shortly! I just had another thought - I had an identical problem in a rented house a few years ago and the landlord got British Gas round. The BG engineer didn't even remove the rad, he managed to fix the issue (somehow) just by tinkering with the boiler itself. Is there any way I could avoid removing the rad or is this the logical next step?

 

[Burnerman]

I would think that unlikely - maybe the engineer was just repressurising the system, or something.
By taking the rad off you'll see how dirty the system is, and ascertain whether or not the valves are working.
I don't know if B&Q sell decorators caps - the valve screw threads may differ. It could be an idea to take a pic of the valve, or determine what make it is.
John