Problem Radiator

Avatar Image
allenlondon | 11:34 Thu 10th Dec 2020 | Home & Garden
23 Answers

Small flat, six rads, 5 fine, red hot, bleed easily.

Last in sequence has been OFF for 3 years (bedroom).

Now want it on. On/off valve stuck. WD40 overnight. Next day valve turned, but only a little. Pipe underneath that valve feels cold.

Tried bleeding. No air, but just cold water.


Mine is to open the bleed valve and draw a LOT of cold water through it.

(Is there a bleed key with a built-in tube that you can direct into a bucket?)

Any other/better ideas welcomed!




1 to 20 of 23rss feed

1 2 Next Last

Best Answer

No best answer has yet been selected by allenlondon. Once a best answer has been selected, it will be shown here.

For more on marking an answer as the "Best Answer", please visit our FAQ.
When you say valve, is it a thermastatic valve?
Question Author
No. On/off switch, where you turn a knob to turn the rad fully off or on.
I expect The Builder will be along shortly to sort you out, but I don't recommend your bleeding solution, because I believe that even if it resulted in the radiator filling with hot water, this would not be replenished once you closed the bleed valve and would therefore gradually cool down.
Question Author
I think the thing that's stuckish is called a Lockshield valve. I will have another go with WD40, and leave it longer. But the biggest pointer is that the pipe beneath the lockshield valve seems cold. Shouldn't it be hot, up to that point?

If the valve has only turned a little, then it needs to be fully open, before you think of doing anything else. Also you need to check that the other valve is open to allow the cooler water back to the boiler.
if it's urgent (is it because mrs a coming home?) get a plug in as a temp solution
If not so urgent, perhaps a heating engineer?
As a rule you would only close the lock shield valve when you are removing the radiator. Otherwise it stays open.
You need to free the on/off valve to get water to flow through the radiator. It may take a bit of elbow grease to release it, so try applying a bit more force. Maybe remove the cap from it and see if you can get something to grip the brass stem and rock it back and forth. A small adjustable spanner or a pair of grips perhaps.
Unless the lock shield has never been right, one doesn't tend to change it because it should be set to balance the system and ensure all radiators have a fair share of the available hot water. I believe it's on the exit side of the radiator so the pipe will be cold if water hasn't flowed through the radiator. Unless you have reason to mistrust it's setting, concentrate on the thermostatic valve side.
These things do stick but be careful using force as you are likely to damage the incoming (or outgoing) copper pipe which is pretty soft. Do that and you will be on the breaststroke before you know it.

The pipe under is may not necessarily be hot if no water is flowing. Bleeding it is most likely just to get water flowing in from the other 'tap' so pointless.

Many valves are two way now so you cannot guarantee inlet or exit, not that you could when they are not unless you put the system in.

The way I generally free them is WD40 as you are doing and with a small spanner direct onto the brass moving to and fro in small steps. But like I say be careful.

The mistake you made is turning the radiator fully off and leaving it off - you should always open it just a crack, otherwise the seal sticks down. Your best plan is to turn off all the radiators except that one, turn the heating on and fiddle the thermostat to make sure the pump is running. The valve on the poorly radiator should be fully on. Feel the pipe on the outlet from that radiator and see if it gets warm. If it doesn't, open the lockshield using a spanner, COUNTING THE NUMBER OF TURNS. That puts the whole power of the pump through that one radiator and should lift the seal and start the radiator working again. Once it is, turn the lockshield back the same number of turns to return the system to normal. The lockshield valve is used to balance the system to ensure that all the radiators get the right supply of hot water regardless of how long the pipe-run to each radiator is.
Sometimes a small sharp tap with a hammer, or similar, will free a stuck valve. But after three years... Hmmm.
Question Author
Ignorance abounds, of course.

Perhaps I haven’t concentrated enough on the thermo valve. If that was stuck down, that would cause problems, wouldn’t it.

I shall WD40 that valve and tomorrow see if it’s free.

Gord. A little learning eh? (A VERY little).
The TRV might be stuck closed. You should be able to remove the thermostatic head, possibly by unscrewing a knurled 'lock ring' where the head meets the valve. If it comes off, you should see a small metal pin in ther centre of the exposed bit of valve; this pin should be sticking up from the valve - if it is not then it is probably stuck down. If possible you might be able to grab the tiny bit of pin with pliers and give it a gentle tug to fre it and make it then possible to pushh down with the plier end and see if it then pops back up, if so then all should be well when you replace the head. By the way, once freed it will probably allow the radiator to get hot rather quickly, which makes replacing the head a bit dodgy on your fingers.
If the pin can't be pulled, then try pushing it down with a small implement like a screwdriver or use a nail as a punch and give it a tap. This might free it.
It may be wise to leave the heating off until the TRV is back in place, to avoid hot fingers. Good luck.
Yes, it's very common for a TRV pin to stick down.
Do what the others have said to open the lockshield valve. Don't rely on the plastic cap. It's not designed to operate the valve.

If you try tapping the TRV pin, then tap it downwards with something like a nail punch or similar.
Occasionally, if you just tap the valve body, the pin may spring back up but leave the stuck seat behind.
Tapping downwards should obviate that.

(With no flow, the pipework will most likely be cold until flow is restored.)
Question Author
Thanks Atheist, Builder. Intelligent suggestions, which I'll do my best to follow!


Allen at 11:47 said it's not a TRV.
bhg... he changed his mind at 13:16 ;o)))
TB - so he did!
Question Author
I have little clue about my radiators...

One end does have a thermostatically controlled valve thing, which does turn, but inside which I do understand might lurk a stuck pin.

The other end of the radiator, which I was (possibly mistakenly) having a pop at, is what I call the Lockshield valve (again a possibly error).

My disability means that I can't kneel on the carpet next to the damned thing and work on it properly - I have to sort of lean down and try to wield my plumber's pliers on the joint.

Plus my poor eyesight makes such wielding a bit dodgy!

Don't get old, BHG.

Question Author
Managed to get close enough to valve to turn the knurled knob, WD40 the stuck pin, tap the side, work it loose, and.....

hot radiator.

Thermo valve still working, so I’ll let it dry out and then turn it off again.

Who’s a lucky boy then?


1 to 20 of 23rss feed

1 2 Next Last

Do you know the answer?

Problem Radiator

Answer Question >>