Its a very simple valve so you cant really stuff it up. Is it leaking around the base or out the top? When was the last time you descaled? Chances are there is a bit of gunk around the "O" ring and maybe on the valve shaft. With no pressure in the boiler take the valve out - carefully - and soak it in citric acid or descaling solution. Even a speck of crud can cause it not to seat properly.Originally Posted by 3822203F520 link=1266736415/0#0 date=1266736415
I suggest replacing the copper washer when you put the valve back in. Also you can use a tiny bit of food grade grease on the "O"ring to help it seal. Not too much or it will stick - or just get a new valve from coffee parts and bung it in. Theyre cheap.
Its easy to forget these tiny "O" rings go hard just like group seals.