How do valve stems go leaky?

Factual Questions
1

I drove my car home yesterday on its 35 mile commute and parked it in the garage. This morning my front passenger side tire was flat. According to the shop, there was no puncture in the tire, I had a leaky valve stem. The tires were brand new in November of 08 and I suppose they have about 10,000 on them.

How do valve stems become leaky? I ask because it just so happens that I had my oil changed yesterday at noon and the printout says “Checked Tires: OK”. Is it more likely that it’s just a coincidence or could the oil change guy have damaged the valve stem when checking the tires?

2

The elastomeric seal in the valve stem becomes brittle with age and oxidation. When someone actuates the valve (by checking the tire pressure), the stem no longer makes a perfect seal - hence your leak.

3

Thank you. Now I know to keep an eye on my tires when the pressure has been checked.

4

This happened to me on Monday. Must be a clandestine band of tire valve attacking terrorists… :wink:

5

There was actually a bad batch of valve stems made in China; they tended to crack at the bases. Millions of the darned things.

http://www.newsomelaw.com/resources/chinese-valve-stem-safety-probe