How does this style of lockshield work?

[btjtaylor]

Hi all

How do I isolate this radiator?

I found the part online listed as "myson euro lockshield with drain off" but I can't see how you lock it

I tried turning the nut on top it's still tight but rad still receiving water



Cheers

 

[Madrab]

Unscrew the top and you should find an allan key/screwdriver slot underneath, tighten down to close.

 

[btjtaylor]

Thank you! I don't know why I couldn't find that online. All the pics just show the nut closed and the myson website is no help.

I was hesitant to remove the cap in fear of causing a flood!