how can i fix a leaky radiator valve?

If the seals are gone in the valve, the only answer is a new valve.Turn the water off, close the fitting on the other side of the radiator (take the plastic cap off and close with a pliers)and close the thermostatic valve fully. With a bowl underneath slowly undo where the valve goes onto the radiator. The water will drain quicker if you open the bleed screw. Once the radiator is empty, and with the valve fully undone from the radiator,still with a bowl underneath SLOWLY open the thermostatic valve. Drain the pipe until all the water stops and then undo where the pipe joins the thermostatic valve.Replace the valve (you can get them at B+Q ,etc),Turn on both sides of the radiator vaves and bleed the system. Check for leaks.

Tony T
December 2008