Leaky Danfoss lockshield valves

[MickyP10]

These are weeping from the cap where the Allen screw is. I've tried a couple of wraps of plumber's tape but they still leak a bit. Can I use general purpose silicone on the threads or do I need a fancy Fernox/plumber's thread seal type compound? And/or any other ideas to stop the weep?

Many thanks

* Second image is a valve from a removed radiator. I had originally thought the Allen screw would come out fully and I'd find an o-ring on the shaft - but they don't come out!

 

[terryplumb]

Fit a rubber blanking washer,or replace the valves.

 

[MickyP10]

Fit a rubber blanking washer,or replace the valves.

Don't want to replace valves as just carpeted but hadn't thought of a washer. Will investigate! Cheers.

 

[Mutley56]

Would this be suitable?
I’ve used similar for temporary blanking off some isolation valves when doing other DIY work. They have a rubber disc in the central recess that provides the water seal.
Get them from Screwfix or Toolstation for example.