If you have a newer vehicle, you may have seen this light on your dash before:

The TPMS (Tire Pressure Monitoring System) light illuminates when one or more tires drops 4 psi or more than the other tires. If it’s flashing it generally indicates a problem with the TPMS as a whole, but if it’s on solid generally a low tire is the problem.

A tire can only be low for one reason: It’s leaking via either a hole, or possibly the bead (area where the tire meets the wheel), a cracked wheel, or a leaking valve stem. Allow me to share my experience with you.

2005 GMC Yukon Denali with 3 tires that leak pretty badly when it gets real cold out. And by “real cold” I mean under 0° F, a time when you really don’t want to be outside pumping air into the tires.

The first thing you’ll want to do is check for any obvious objects/punctures…like I found in the right rear wheel, which oddly enough is the one that leaked the least of the four.

Now, the position of that nail is too close to the shoulder for the now standard method of repair called the plug ‘n patch, which is exactly what it sounds like. The patch would rub through the inner liner of the sidewall in my case, which would ruin the tire. I threw a plug in it (shops won’t do this anymore) as I do not wish to buy a set of tires for the truck because of the fact that it’s AWD (All-Wheel Drive). There’s a blog I wrote about the reasons behind that.

If you don’t find a puncture in the tire, the next step would be to spray the tire with a soapy water solution to watch for bubbles (unless you have a dunk tank which also works pretty well…a bathtub would also work, but I’d imagine your significant other may not be too happy with you if you used that).

This is my left rear wheel, which was the one that leaked the worst. Turns out it was leaking from the base of the TPMS valve stem as seen in the next picture.

All those bubbles at the base of the stem indicate the leak is there. Not unusual, as these are alloy wheels and corrosion builds up. Also, there’s a rubber seal at the base and this becomes brittle and can leak. You’ll see this seal later on.

If that’s not leaking, look for bubbles around the bead on both the inside and outside of the wheel. This is my right front wheel. Look a little closer…

Gotcha! Found the leak on that wheel for sure! The leak here is due to corrosion on the wheel lip, where the tire sits on the wheel. Here’s what it looks like with the tire removed:

 

You can see on the bottom left of the picture where I’ve already ground some of the corrosion off with a wire wheel, but look to the right at what it looked like before.

I figured it was a good idea to clean the corrosion off all four wheels and service all four TPMS sensors while I was at it. Some people also choose to add a bead sealer to the wheel, I decided to skip this in the event my tire plug fails and I need to replace the tires. Servicing the sensors goes like this:

Some people choose to remove the nut on the TPMS stem and let the sensor drop into the tire before it’s dismounted, I chose to do this after I removed the tire. With the nut removed, the sensor can be pulled out and the seal can be replaced.

The kits are really cheap and are usually available from your local parts store. I picked mine up from O’Reilly Auto Parts and they came like this:

Sorry for the blurry pictures, but hopefully you get the idea. Very simple. You get a retaining nut, the stem seal, a stem cap, and a valve core.

It’s worth noting that you must be VERY careful when removing and reinstalling the stem nut as the sensor it screws onto is a thin aluminum and can snap or the threads can strip very easily. If this happens, you’ll need to buy a new TPMS sensor which is usually around $75.

Hopefully this helps explain what the term “bead leak” means and what needs to be done to fix it.