Originally Posted by
freeranger
The valve core (assuming Schrader) is easily replaced. Think they're universal, so any local tire store should have one. Or just replace the tube, and while the tire is off, run a dryer sheet around the inside of the tire to see if there is a thorn or anything in the tire. Dryer sheets are great for this-they will snag on almost anything! Could be that if there is something in the tire/tube, when whatever it is, is positioned so it's on the floor, the pressure from being on the floor is acting like a "plug", allowing only a slow leak. When not on the floor, could allow more air to escape, as there is not pressure on it, so you lose the "plug" effect.
Well, I was going to do the spit test on the valve last night, but it turned out to not be needed. I pumped up the tire to get some pressure in it, and then when I disconnected the pump, I heard the hissing of escaping air. I originally thought it was the valve core again and tried again to tighten it, but soon realized that the air wasn't coming out of the valve, but rather from a leak inside. It seems to be the valve stem itself. When I would twist the stem, the escaping air would either speed up or slow down depending on which way I twisted it. I guess this means having to replace the inner tube. A leak where the stem meets the tube can't be patched, can it?
One other question this leads me to is about how this could have happened. The only thing I can think of that could cause a leak between the valve stem and tube is when I pull the nozzle off of the stem after pumping up the tire. That's the only thing that puts a lot of pressure on it. Sometimes the nozzle is really hard to remove. Is there a way to fix that? I'm pretty sure that the current problem was simply made worse by my pump. Before, the leak took about 24 hours to make the tire low enough to need inflation. Now I pump it up and it only takes about 2 minutes to go completely flat. This change happened suddenly after I pulled the pump nozzle off the valve stem last night.