Last night I was away from home and noticed I had a tire that was low on
air. I went to the nearest gas station and added air. Thats when I
noticed the air was coming back out of the tire valve on the stem. I
suspeced a loose valve, but had no tool for that with me. Being only 5
miles from home, I overfilled the tire by about 10lbs put on the cap
(which slowed down the leak), and drove home without any problem. Once
home, I got out my valve tool and tightened it. That did not solve the
problem. I went out to the shed where I have several usable tires that
I plan to sell at the next rummage sale because they dont fit any of my
vehicles. I removed a valve and placed it into the leaky tire. I was
sure this would solve the problem. It didn't. The tire still leaks at
the valve. So I went and took out yet another valve, and changed it
again. The sucker still leaks.......

I'm confused. The air is leaking from the valve. Not from the stem,
such as around the rim, or a crack in the stem. Putting the cap on the
stem slows down the leak considerably, so that alone proves 100% that
the leak is the valve, and not anywhere on the stem.

Yet, three different valves and it's still leaking. Both those valves
came from tires that were holding air.

How can this be?
Over the years I've had tires that had either loose valves, or bad
valves. If tightening the valve did not fix the leak, a valve from
another tire always did.

This is making no sense at all.....

Yea, tomorrow I'll take it to the tire shop, but this has me puzzled....

(Since this happened on Halloween, I can only suspect ghosts, because
this just makes no sense at all otherwise)....