Achey Breakey Parts: TPMS And Corrosion
What you need to know to avoid the pain.

Problem: Metal Valve Caps.

While the bright and shiny chromeplated or metal valve caps that you see everywhere are often a nice effect compared to dull black plastic caps, when it comes to TPMS stems, they're a clear and present danger. Metal caps can easily cause corrosion on the threads of TPMS stems as well as beginnning to corrode themselves. The result is all too often that the cap will rust-weld itself to the stem, leading to outcomes from the cap simply seizing when a technician tries to remove it, to crossthreading issues, or even having the stem break off entirely. When the valve stem is a nonremovable part of the TPMS monitor, this goes from being a minor issue to a critical and often expensive problem.

Solution: Rubber Valve Caps.

It's simple: Do not ever put metal valve caps on your TPMS valve stems. Black plastic or rubber caps may be dull and boring, but boring can be good. Having your expensive monitors turned to junk by corrosion is excitement you don't need. As Barry Steinberg from Direct Tire told me, “Initially they were putting out a lot of metal caps on these metal valve stems and they were seizing and cracking and breaking. But ever since they've all gone to rubber valve caps we've seen a lot less of that.”

Problem: Air, Water and Salt.

The last reason that TPMS valve stems corrode is simply unavoidable. Stems are exposed to the air, they get wet, and especially in winter conditions they get exposed to road salt and salt water. Corrosion is just a fact of life when it comes to metal parts, and valve stems are exposed every minute of the day. Collet nuts, the parts that screw down over the valve stem to tighten the whole assembly against the valve stem hole are especially vulnerable to the same kind of corrosion that can cause a valve cap or valve core to seize. Horror stories abound of collet nuts seizing, valve stems breaking at the slightest pressure applied by tire techs trying to remove them, and even of stems breaking off while the vehicle is in motion.

Solution: Proper Maintenance.

The only solution to environmental corrosion is constant vigilance, mostly in the form of service packs. Service packs are small packets that tire dealers and installers keep with all the tiny parts and widgets that need to be replaced every time your tires are serviced. These packs will include:

A new nickel-coated valve core.
A new rubber or plastic valve cap.
A new set of rubber gaskets to seal the valve hole in the wheel.
A new collet nut.

Service packs, you may note, therefore cover all of the major reasons for corrosion problems I have already noted, that being the major reason they exist. By replacing each of these parts every time your tires are serviced, you keep corrosion at bay, preventing it from gaining a foothold in the cracks and crevices between all these seemingly insignificant little parts. This is why the service packs are so important, why responsible installers will always replace them, and why you should always resist the temptation to save the small fee that they will have to charge you for doing so.

There is also a much more permanent, if somewhat more expensive way of solving TPMS corrosion problems, which is to replace your first-generation TPMS sensors with second-generation aftermarket sensors. Most aftermarket sensors now use a removable snap-in rubber valve stem that not only completely avoids most corrosion problems, but can be easily and cheaply replaced if it is damaged. This is an especially good option to look at if your sensors are more than 6 years old, as the batteries on TPMS sensors are rated to last about 6-7 years, and cannot be replaced. That's another headache entirely.

Complete article - http://tires.about.com/od/Tire_Safety_Maintenance/a/Achey-Breakey-Parts-Tpms-And-Corrosion.htm