Let me give you a quick tip.
Assuming you see the water valve, disconnect the wire and remove the 4 slotted screws (make sure pressure is relieved, either a cold engine or remove the pressure cap from the tank),
Then pull up the valve "guts" (by the shiny part inthe center), you will see the rubber diaphragm, make sure it isn't ripped. I will try to find a picture online of what it looks like if it's ripped.
If it is you buy a repair kit.
Link to thread here showing bad diaphragms (whole thread worthy of your review):
http://www.peachparts.com/shopforum/diesel-discussion/246273-damaged-mono-valve-pictures-please.html