drayton TRV4 leaking

[happypig]

I have 8 radiators with Drayton TRV4s which were fitted in 2002; At least 5 of them are leaking very slightly. A couple of them leak when they are adjusted but then seal up again, another couple show evidence of leaks but feel dry and one is almost permenantly leaking (very slightly and it evaporates from the cup I put there to catch the drips).
The system is pressurised and has Fernox MB1 in it.

Are the valves just worn out, faulty or is there some inconsistency with the system/inhibitor ? Is it fixable, or do I need new valves ?

oh, the leaks show like this if it's any help :

 

[gremlin16]

They look heavily calcified?

 

[ChrisR]

Looks like you need new valves, which is disappointing. I'd be cross with Drayton.

 

[gasandoilman]

thingk you should drain down and change them fill the system with inhibitor i use x100

Use honeywell valves so you can change body without draining down
you need a tool(epensive) but if you call honeywell they would put you onto there rep who lets you use his