I just got back from a 3,000 mile road trip (25mpg) and had three (3!) flat tires.

Twice, I ran over screws/nails. I'm obsessed enough to check my tire pressure every day while on a road trip, so I noticed the first screw before the TPMS lit up. I had the leak repaired at Sears.

The second screw (another tire) must have been used to hold up a building because it was HUGE. The whomp, whomp, whomp sound freaked me out, so I stopped and saw the giant screw. The TPMS still had not lit up, but I hustled to a Firestone store a couple of miles away. When I got there, the screw was gone and the tire pressure was 40psi, so I thought that by some miracle I had evaded a flat tire. I left Firestone, went to lunch and when I came out the tire pressure was 27. SO... I went to Wal Mart and they did a fairly lame job of fixing it (they used 4 tire weights).

Anyway, on the 2998th mile of my 3000 mile trip, the TPMS lights up and when I get home I see that the FIRST flat tire is flat again. The weird thing is that the valve stem won't close. I check the pressure (25ish) and then the air just keeps coming out of the valve. I have to poke it 8 or 9 times to get it to seat.

Does this happen to anyone else? I'm going to have the valve stem changed tomorrow. Hopefully, that was the leak. The drag is that the new tire warranty isn't in effect because the tire was repaired, which voids the warranty. Ah well.

Three flats in one trip. I don't think I've had 3 flats in my life.

Wow, sounds terrible. And in answer to your question, no. (I've never had that happen.)

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I've never had this happen either and I have almost 45,000miles on my original tires with only 1 flat - my wife ran over a nail...)

Is it possible the the repair place replaced the valve stems if they dismounted the tires when they repaired them? Also.... I've always wondered if you slime a tire (which as has been discussed is a bad idea if you have TPMS)--what stops it from gumming up the valve stem?

I have seen valve stems freeze up from using wet air out of a compressor. The expanding air drops in temperature and freezes in the stem. This can happen in temps warmer than freezing but it will quickly melt. At sub-freezing temps it could persist.

If you have a problem with the valve stem sticking or leaking at the valve (not at the rim) you could always just change the valve. Buy them and a valve stem tool at any auto parts place. Beats having the tire unmounted and remounted.

Just had the problem on my 2007 camry hybrid. 8600 miles or so and the driver side rear tire valve would not close after I added about a pound to the tire. No matter what I did I couldnt get it to close, so I put on the spare. I have never expereinced this before....

I have the pressure sensing factory valve stems in place. Will go to Toyota tomorrow.

The TPS sensors are NOT in the valve stems. They are wrapped around the rim. There is a picture of them in your manual somewhere. So at least when you get the valve stem replace it will be a normal cheap one.

Another "hasn't ever happened to me", though I have acquired two flats -- both from nails due to construction in the area. Both repaired (not slimed) but my favorite Ford dealership. Both of my tire punctures/flats were detected by the TPMS long before the tire was visually (or audibly, while driving) flat, btw. No issue with value stems; I check my tire pressures about once a month, year-round.

- Shannon (Geeky, Wild Texan)

Just to update you guys...

Went to Toyota, and the manager did not believe me about having a bad valve until he saw it himself. Even then, he just said that "water must have got in there and frozen, keeping the valve open".

Now this was several days after I had taken the tire off the car, and I always had a valve cap in place, and I had already filled 2 tires with that same air hose, so his explanation dosent make sense to me. Also, he said that this might not happen to me again for another 3 or 4 years as it is pretty rare.

Well I have been driving cars for about 10 years now, and that has never happened to me before, and I have driven without valve caps, and I drove 2 years in frosty Buffalo, NY with its lake efffect snow and never had that happen to me and never heard about it happening.
That combined with the fact that although the dealer said ice was the issue he also said he would replace the valve under warranty makes it seem to me that the valve was defective.

In any event, I am back on a real tire now and I am very happy to put the small spare back in the trunk.

It sounds like one of those "I have no idea why it failed" answers. Dirt, ice, anything could have stopped up a valve stem. It might have even come off the last compressor nozzle you used... or it could have been a bad valvestem. But for the cost of a valvestem it wasn't worth trying to figure it out.

At least its fixed now and I don't think you'll have any more problems. I doubt its the sign of any implicit problem with the valvestems. You probably just got UNlucky. There are always going to be a few defective parts out there unfortunately.