| Find it with | Soapy water on the tread, valve, and rim edge, tire inflated |
| Repairable? | Only tread punctures under 1/4 inch; sidewall and shoulder never |
| The proper fix | An internal combination patch-plug, tire dismounted at a shop |
| Plug or sealant | Temporary and emergency only, not a permanent repair |
| No visible nail? | Usually the valve stem or a corroded rim bead, not the tread |
A slow leak is the tire problem that hides in plain sight: the tire is fine one morning and low the next, with no obvious cause. The fix depends entirely on where the air is escaping, so the job is really two steps, find it, then fix it. A slow leak is worth handling promptly, because running a tire low wears it unevenly and, per the U.S. Department of Energy’s fueleconomy.gov, wastes fuel as well.
The repair rules and figures below follow tire-industry guidance. If you have not confirmed the tire is actually leaking rather than just reading low, our guide to why your car tires keep losing air covers the difference, and if the pressure only drops in the cold, that may be temperature rather than a leak.
Table of Contents
Where is the leak coming from? Find it first
Finding the leak comes before fixing it, because a slow leak has four common sources and each needs a different fix. Inflate the tire to its correct pressure, then use soapy water to check the tread, the valve, and the rim in order. The bubbles will show you exactly where the air is escaping.
- Inflate the tire to the correct pressure. A leak shows up best at full pressure, so top the tire up to the cold PSI on the driver’s-door placard first. Our guide to the correct tire pressure for your car shows where to find it.
- Brush or spray soapy water over the tread. Mix a little dish soap with water, wet the whole tread, and watch for bubbles growing at a nail, a screw, or a small cut.
- Check the valve stem and core. Wet the valve and the base where it meets the wheel. Steady bubbles there mean the valve is leaking, not the tread.
- Run the soapy water around the tire-to-rim bead. Bubbles where the tire meets the wheel point to a bead-seal or rim-corrosion leak rather than a puncture.
- Mark the spot. Circle the leak with chalk or a crayon so you, or the shop, can find it again once the soap dries.
Caution: if you raise the car to inspect a tire, support it on jack stands and never rely on the jack alone. A car that slips off a jack can cause serious injury.
Fixing a tread puncture (nail or screw)
A nail or screw in the tread is the most repairable kind of slow leak, but the right repair is not the roadside plug most people picture. A temporary external plug can seal a small tread puncture to get you to a shop, and it buys you time, not a permanent fix. The lasting repair is a combination patch-plug installed from inside the tire, which means the tire has to come off the wheel.
Per the U.S. Tire Manufacturers Association, a puncture is only repairable if it sits in the tread area and is no larger than 1/4 inch (6mm) across. A proper repair requires removing the tire from the rim, inspecting the inside for hidden damage, then filling the puncture with a plug and sealing the inner liner with a patch. A plug on its own is not considered a permanent, approved repair. Do not pull the nail out until you are ready to repair the tire, since a plugged nail is often holding back most of the air.
Leave the permanent repair to a shop, because dismounting and inspecting the tire is the part that makes the fix safe, and it is not a driveway job for most owners. If you use a plug to get moving, keep your speed down and have it repaired properly soon. For the full difference between the two methods, see our guide to tire plug versus patch.
Fixing a leaking valve stem or core
A leaking valve is a common slow-leak source that has nothing to do with the tread, and it is easy to miss. The rubber valve stem hardens and cracks with age, or the small valve core inside loosens and weeps air. A loose core can sometimes be snugged down with an inexpensive valve-core tool, but a cracked or perished stem needs replacing.
Replacing a valve stem is a cheap job, and it is usually done with the tire off the wheel, so it often gets bundled in when a tire is dismounted for another reason. If your tire keeps going down and the tread looks clean, wet the valve with soapy water before you assume you have a puncture. On many cars the valve is also part of the tire-pressure sensor, so a shop will use the correct service kit when they replace it.
Fixing a rim or bead leak
A leak where the tire meets the wheel is a bead-seal leak, and it is one of the top answers to “my tire keeps losing air but there is no nail.” Bubbles along the rim edge usually mean corrosion or debris has broken the seal between the tire bead and the wheel, which is common on older aluminum wheels. The fix is to dismount the tire, clean the corrosion off the bead area, and reseat the tire with fresh sealer.
Leave a bead reseal to a shop, because it requires taking the tire off the wheel and cleaning the sealing surface properly. A wire-brushed, resealed bead usually cures the leak, but if the wheel is badly corroded or cracked it may need to be replaced. This is the kind of leak that a tread plug or a can of sealant will never fix, which is why finding the true source first matters so much.
Should you use a tire sealant, the kind in a can?
A can of aerosol tire sealant can get you rolling again in an emergency, but treat it as a roadside-only, temporary fix. Sealant coats the inside of the tire, which can complicate or prevent a proper repair later, and on some vehicles it can coat and interfere with the tire-pressure sensor inside the wheel. It also does nothing for a valve or bead leak.
If you do use sealant to reach help, tell the shop you used it so they can clean the tire before repairing it. For the wider question of whether to drive on a compromised tire at all, see our guide to whether you can drive on a flat tire.
When should you just replace the tire?
Some slow leaks are not repairable at all, and trying to patch them is a safety risk. Replace the tire rather than repair it in the situations below, which follow tire-industry and NHTSA guidance.
| Situation | Repair or replace? |
|---|---|
| Nail or screw in the central tread, under 1/4 inch | Repairable with a proper internal patch-plug |
| Puncture in the sidewall or shoulder | Replace; this area cannot be repaired |
| Puncture larger than 1/4 inch (6mm) | Replace |
| Two punctures close together, or overlapping repairs | Replace |
| Tire was driven flat or run very low | Replace; the internal structure may be damaged |
| Tread already at the 2/32 inch wear bars | Replace; the tire is worn out anyway |
The sidewall rule is the one that matters most for safety. The sidewall flexes constantly and has no steel belt behind it, so a patch there fails, sometimes suddenly at speed. Per NHTSA, a tire is also due for replacement once the tread reaches 2/32 inch, marked by the built-in wear bars, so a worn tire with a leak is usually not worth repairing. If only one tire is damaged, our guide to replacing just one tire covers whether you can, or whether you need a pair.
Frequently asked questions
How do I find a slow leak in a tire?
Find a slow leak by inflating the tire, then brushing or spraying soapy water over the tread, the valve stem, and the rim edge, and watching for bubbles forming at the leak. Bubbles on the tread mean a puncture, bubbles at the valve mean a valve leak, and bubbles at the rim mean a bead-seal leak. Mark the spot before repairing.
Can I fix a slow leak without removing the tire?
A temporary external plug or a can of sealant can seal a tread puncture without removing the tire, enough to reach a shop. The proper, lasting repair still needs the tire dismounted so it can be inspected inside and sealed with a combination patch-plug. Neither a plug nor sealant fixes a valve or a rim-bead leak.
Why does my tire keep losing air with no visible nail?
A leak with no nail is usually the valve stem, the valve core, or a corroded rim bead rather than the tread. Wet the valve and the rim edge with soapy water and watch for bubbles, since those two spots are easy to overlook. Cold weather also lowers pressure without any leak at all, so rule that out first.
Is a slow leak safe to drive on?
A slow leak is manageable short-term if you keep the tire topped up to the correct pressure, but it is not something to live with. A tire running low loses grip, wears unevenly, and can fail more suddenly if the leak worsens. Top it up, keep an eye on it, and get the source fixed soon rather than refilling it for weeks.
How much does it cost to fix a slow tire leak?
Fixing a slow leak is usually inexpensive. A professional tread-puncture repair, meaning a combination patch-plug, often runs about $20 to $45 per tire, and replacing a leaking valve stem is cheaper, frequently bundled in when the tire is off the rim. A rim-bead reseal costs more for the labor, and a sidewall leak means buying a new tire.
What to do now
Start with soapy water and find the source before you fix anything, because the repair depends entirely on where the air is escaping. A nail in the tread can be repaired, and the proper fix is an internal patch-plug at a shop, not a roadside plug left in for good. A leaking valve or a corroded rim bead is a different job, and a sidewall leak means the tire gets replaced. Keep the tire at the correct pressure until it is fixed, and do not count on a plug or a can of sealant as a permanent repair.
For everything else tire-related, see our complete car tire guide, and for the rest of the car, our car care and troubleshooting hub.
