Fancy Rad valve stuck

[rjm2k]

Bathroom radiator has these type of valve, the rad is cold and one of the valves seems to be stuck, it moves maybe half a turn compared to several turns on the opposite side. I assume there's a replaceable washer in there if I take off the head and that it's likely to have jammed or something, is that correct?

View media item 68628
thanks

 

[Madrab]

Either the thread inside is damaged or worn or what sometimes happens is the washer inside becomes over compressed and when turning the valve off the tap thread inside is tightened past the point it should be and the valve jumper becomes jammed.
View media item 65776The jumper hex (arrowed on the left) pops out of the valve body (on the right) and becomes misaligned and jams, it won't draw back up, ergo, the valve only turns a little.
It can be fixed and new washer fitted but it does mean draining the CH down past that radiator so the valve can be removed.

 

[rjm2k]

Thanks, it's upstairs so I'm hoping that by turning all the other rads off at both valves , closing the feed from the header and maybe capping the vent there should be minimal draining down needed.

 

[Madrab]

If it's gravity fed and you can bung the F&E cistern and vent then you may have minimal draining, just the rad itself. Certainly worth going ahead on that basis if you are happy with the tap servicing. Of course without stripping down the tap you won't know if it's worn or not and whether a replacement will be needed. May be worthwhile having just a plain lockshield on hand to get it working in the short term if it's beyond servicing.

 

[rjm2k]

Managed to take it apart to check it, no problems found, put it all back together and it's now working fine.