1999 Jeep Wrangler proportioning valve in front of booster

I have a small wet looking area (very small) at the front of the proportioning valve .. It appears to me that this PV may be leaking .. What would be the proof that the valve is bad... ?? Can this valve be removed and the guts taken out and this plunger taken out and the hole be welded closed.. I don't do off road and brakes from the past did not have this P. valve >> Is there any cure to my problem other than buying a new prop. valve ?? The power booster works fine and the lines are in tact and the wheels do not appear to have a brake fluid leak...
Thanks for the help and nice web site. Walt