Cold radiator

Money_Saver

Hi
one radiator is stone cold. All others are heating fine. I’ve turned all other radiators off and the pipe by the thermostat radiator valve gets hot and a small part of the lower radiator and that’s it. 

I’ve bled the radiator and all that comes out is water which is clear.I’ve opened the other end and nothing happens. I have removed the thermostat valve and the pin is stuck. I’ve undone the nut which makes the pin more free but still not enough for any heat to come through.  I have a system boiler. 

The other day plumber changed the 3 port valve as we had no heat only upstairs when the hot water was on. 

Can anyone suggest anything?

Jeepers_Creepers

Looks like you've done most of the essential checks.

You have opened the 'other' end valve - the lockshield - a good further couple of turns? (You should always check to see how far open it is to begin with, so it can be returned to that point - that's what balances a system. So first turn it fully closed, counting turns and part-turns it took to get there, usually in the order of 1 to 2 turns if the rad is close to the boiler. Note this down and stick it on the valve!).

That leaves you with the TRV valve, which you've said has a sticky valve. A normal valve 'pin' should require a firm push to press it down (you'll need something over your thumb so's it doesn't hurt...) but should move completely smoothly and then 'bottom out' with a firm 'thunk'. On release, it should pop back up instantly.

Slackening that gland nut should have helped loosen it, but the best thing now would be silicone lubricant spray which you can get from most hardware stores or places like Screwfix https://www.screwfix.com/p/flomasta-silicone-spray-200ml/6699x

Spray the pin liberally - allow a nice pool around the pin base - and move it up and down repeatedly until it's free-moving. Nip the gland nut back up afterwards to prevent leaks from there.

Does the pin now have a smooth movement with a firm thunk on t'bottom and an instant pop-up? Does your rad heat up?

If you suspect the pin is not acting along with the 'seal' which controls the valve - ie the seal is still stuck closed - then use a rubber mallet or piece of wood to repeatedly strike the side of the valve body (with the TRV head off). It might go 'clunk' as it releases.