Question about slow tire leak and maintaining TPMS

If you have cast wheels, the most common source of leaks are around the beads. Clipped-on wheel weights scratch the protective coating on the wheels leading to corrosion. On steel wheels, rust pits form under the bead. Both of these conditions are not likely to be found on a vehicle as new as yours. I actually have rust holes right through the steel wheels on my 25-year-old Grand Caravan. One tire goes flat overnight and the other loses about 10 psi per day. Pumping them up every day when it's 15 below zero is miserable but I have to do that until I can find a good set of used wheels.

Stick with whatever caps came with the pressure sensors. All of the parts were designed to work together to reduce corrosion. Any two different metals and an acid, like road salt, form "galvanic action" just like in a battery, and that means corrosion. If the body of the sensor is made of aluminum, the valve core will be too, and the cap will be aluminum or plastic.

First you want to be sure what's leaking. If it's around the bead, there is a sealer for that but it involves dismounting the tire to apply the tar-like material. It fills in the gaps and pits caused by rust. If you do indeed have a leak in a sidewall, see a tire store first that handles that brand to see if it can be replaced under warranty. If not, as a last resort there are chemicals that are added through the valve stem that will seal a small leak. Check first if those are safe to use with pressure sensors. Those sensors work by comparing the pressure to atmospheric pressure and there has to be an open port to both. Also, once those chemicals are added inside a tire, it is almost impossible to apply a patch to fix a larger leak like from a nail. The glue will not adhere to the rubber once that chemical is on it. Plugging a hole AND patching it is a better procedure but plugs won't adhere either when that chemical gets in the hole.

There is no valve stem cap that will protect your tpms sensor that iam aware of.The best way to do that would be to have nitrogen put in your tires.the nitrogen doesnt contain all the water that compressed air does keeping the sensor from all that exposure. Also the nitrogen mocules are larger then compressed air so air pressure loss is much slower and pressure is more stable.The nitrogen doesnt heat up while driving and outside temp etc so it doesnt raise and lower the pressure in the tire like compressed air.Now for your air loss your going to have to remove the tire get a spray bottle with soap and water in it.Then spray down the bead of the tire side walls valve stem etc looking for bubbles.But I have seen tires only leak with the weight of the vechile on it while driving etc.I dont like driving around on a known leaking tire because if the leak worsens and the pressure loss is great enough and tire damage is done you could have a blow out.

The problem is that when I bought my van used last year, two of my tires' valve stem caps were missing. I had a TPMS light come on a few months ago, and the mechanic was able to replace it and entire job was about $200. He also told me that I should put plastic (not metal) caps on the valve stems, since they protect them and the sensor from dirt and moisture. I bought plastic caps and the package I bought them in claimed that there were TPMS safe. But then I found out that there are plastic caps (I think it was made by a company called Schrader) with some sealing material in them that prevented moisture. So now I am trying to figure out whether or not I should get Schrader TPMS Plastic Sealing Valve Cap or just leave the ones I have?

Yes, I plan to go to Costco to replace all four of my tires and have them put in nitrogen, but that would probably be 5 to 6 months from now. Tire replacement costs around $450. The van has carried heavy loads in this condition, but the leak seems to be very slow and constant. I know for a fact that once the side of the tire rolled over a pretty sharp corner of a big concrete block and I think that might's punctured it; I saw a very small hole. I am not sure whether just adjusting the pressure every few days for the next 5 to 6 months is a good idea.

I hope my wheels are okay. I noticed that for at least one of the wheels, the center of the wheel had its shiny part coming off in spots. Is that something to be concerned about?

As far as the caps keeping moisture out there is plenty of moisture in the compressed air in the tire so as far as caps I would just use the common plastic ones.As far as the tire loosing air I would worry about the leak getting worse and the tire loosing enough pressure to cause sidewall damage and blow outs.I would fix the leak if it were my tire.As far as the rim it could just be clear coat coming off the wheel.Without seeing it cant say for sure.

Oh okay, so I'll just use the plastic ones. Instead of soap and water spray bottle, can I use some tape such as duct tape or electrical tape and put it over what I think is the hole and see whether the leak stops or slows down to make sure that's the problem? Is clear coat coming off a sign that corrosion will start soon and should I get the wheels properly coated?

No you need soap and water in the spray bottle to find the leaks.if you have alloy wheels and loose the clear coat they can oxidize.

I hope the oxidation does not lead to rust and more leaks. Is there a way to prevent this?

Do you have aluminum or steel wheels.

I actually am not sure whether I have aluminum or steel wheels. But what would I have to do if I have aluminum wheels and what would I have to do if I have steel wheels? Also, is there a way I can find out whether I have aluminum or steel wheels?

You can use a magnet if it sticks you have steel wheels if it doesnt you have aluminum. With steel you would have to strip the paint clean the metal and repaint.With aluminum strip the clear coat clean the surface and re coat with clear coat.

Oh okay. I will try to use a magnet, although I am worried that if I use a magnet, can something happen to the TPMS sensor? And how long should I leave it before whatever corrosion happens becomes irreversible i.e. what are some signs that tell me that it's getting late to recoat or repaint the wheel?

You're getting way too worried over something you aren't going to stop, especially if you live where they dump a pound of road salt on an ounce of snow like I do. If you have cast wheels, which are most commonly used now because they're lighter, the best you can hope for is to have stick-on wheel weights used when the tires are balanced. All tire changer machines are designed to no longer scrape on the edge of the wheels when they pull the tires on and off. That, and using stick-on weights will make the clear-coat last the longest, but if you look at any car in any parking lot, you're going to find corrosion around the edges of the wheels, . . . and no flat tires. My painted steel wheels lasted 25 years before one developed a pinhole from rust last summer. The paint was flaked off over ten years ago. I also have a '95 model with cast wheels. They're full of corrosion but have no leaks. I'd be more concerned about having the leaking tire's sidewall checked. If there's a leak in the tread area, the tire can usually be patched, although I prefer to plug the hole first to keep water out, then patch it from the inside. Patches do not hold well on the sidewalls because of the constant flexing. Most people won't put plugs on the sidewalls either but I have had them hold on my tires.

I've also tried to repaint steel wheels on collector cars, and it doesn't turn out as good as the factory job. They got to start with a perfectly clean wheel, not one that has been attacked by salt and car wax.

The people at any tire and alignment shop will find the source of the leak in a minute or two, usually without removing the wheel from the vehicle. Once the tire has been inspected and the leak resolved, go out and enjoy your van and forget about the wheels unless you're a perfectionist about how they look. If that is the case, buy a set of new wheels with new tires, and switch to those in the summer and put the current set on in the winter. That used to be somewhat common up here in the snow. When a wheel finally does start leaking due to corrosion, in about another 15 years, it's going to start out very small, and your pressure monitoring system will let you know. You'll have days or weeks of warning before the tire gets so low that it's dangerous. At that point any repair shop that mounts tires will have a can of bead sealer sitting on the shelf just waiting for you. Every parts store sells it and every shop uses it. Your mechanic will tell you when there's so much corrosion on the wheels that you need to be concerned. Until then, there's no sense worrying about it.

Thanks for your advice. I think the hole on the sidewall is so small that even the mechanic didn't say that was the problem. I remember the side of the tire rolling over the corner of a big cement block and sliding down, and then after cleaning the dry cement off the side of the tire, seeing a hole at one spot. I think the sidewall got injured enough that I am just going to have to change the tires.

The funny thing is my right rear tire suddenly developed a leak in the sidewall about a month ago. Drove all over the county one day, stopped at Home Depot, and when I came out I noticed my van seemed to be not sitting level. Expected to find it sitting in a hole but turns out the tire was half flat. I nursed it home ten miles, and just by luck, it had gotten warm enough to melt the snow, and I saw it bubbling and hissing. I didn't hit anything but the tire was well worn out. I threw on another used tire, and it had been fine until today I noticed it's half flat again. Now I have to pump up three tires every day. Not much fun when it sits outside in a snow bank.

I heard that when a tire goes flat, the TPMS sensor can get damaged if it happens to be at the bottom where it can get compressed underneath the wheel. I am going to keep checking all the tire pressures everyday until getting a chance to change them. Pumping tire pressure everyday might have been okay but there's no guarantee that with the flexing sidewall and something that looks like a problematic hole my tire's problem is going to stay the way it is and not get worse.

No respectable mechanic fixes sidewall punctures. It's not safe.

Okay. Best thing to do is replace the tires.