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How Do You Find a Leak at a Valve Stem or TPMS Sensor Stem?

Spray around the base of the stem where it passes through the wheel, and flex a rubber stem to open any cracks. Bubbles at the base

3 min read CHAOS Moto

To find a leak at a valve stem or TPMS sensor stem, spray Bubble Check around the base of the stem where it passes through the wheel, then gently bend a rubber stem to one side and spray again. Bubbles at the base mean the stem seal or grommet is leaking; bubbles from a crack in a rubber stem mean the stem needs replacing. On a clamp-in TPMS stem, a leak at the nut and grommet usually calls for a new service kit.

Find your leak in 3 taps: Leak Lab →
Wheel diagram: dashed red circle around the base of the valve stem with a ring of small bubbles Valve stem / TPMS stemSPRAYBase of the stem atthe wheel, nut, grommetLOOK FORA ring of bubbles atthe base, or at a crackNEXTNew stem, or new TPMSservice kit to spec
Valve stem or TPMS stem: spray the base where it passes through the wheel. Flex rubber stems to open cracks.

How does it show up?

  • A slow leak on a car with older rubber snap-in stems, which crack with age, heat, and ozone.
  • A leak at a clamp-in TPMS stem after tire service, from a loose nut or a worn grommet.
  • Corrosion around an aluminum TPMS stem.
  • A TPMS warning with no obvious puncture.

Where do you spray Bubble Check?

  • The base of the stem where it passes through the valve hole on the outer face of the wheel.
  • The body of a rubber stem. Bend it gently to one side, then the other, and spray each time.
  • On a clamp-in TPMS stem, around the nut, washer, and grommet.
  • The open end too, cap off, to rule out the valve core.

What do the bubbles look like?

  • A ring of small bubbles around the base of the stem.
  • Bubbles from a crack in the rubber that only open when the stem is bent.
  • Bubbles creeping out from under a TPMS nut or grommet.

What do you do next?

  1. Mark the stem and note which part leaked: base, rubber, nut, or core.
  2. For a rubber snap-in stem, replace the stem.
  3. For a clamp-in TPMS stem, replace the service kit and tighten the nut to the sensor maker's torque spec. Replace a corroded stem or sensor as the sensor maker directs.
  4. If a sensor was replaced, complete the TPMS relearn for that vehicle.
  5. Inflate and spray the stem again to confirm.

How to run the check

  1. Inflate the tire to its specified pressure. A soft tire may not push enough air to show a slow leak.
  2. Spray Bubble Check on the area and give it time. A slow leak can take a little while to show.
  3. Watch for bubbles that keep forming at the same point. The first light foam from the spray settles; a leak keeps building.
  4. Mark the spot with a tire crayon before you wipe the area dry.

About Bubble Check

Bubble Check is the CHAOS Moto spray-on tire leak detector. It comes in a 32 oz bottle with a trigger sprayer, so you check the tire on the wheel with no dunk tank needed. Shops use it to pinpoint valve and bead leaks and for TPMS stem checks. See the Bubble Check page or where to buy. Bubble Check is not currently sold on Amazon.

Common questions

Can you reuse a TPMS grommet?

Follow the sensor maker's instructions. Many call for a new service kit whenever the tire is serviced.

Can Bubble Check be used on TPMS valve stems?

Yes. Spray it on TPMS valve stems and service points to pinpoint a leak with no dunk tank needed.

Why do rubber valve stems leak?

Age, heat, and ozone crack the rubber, and the crack often opens only when the stem bends. Flex it while you spray.

More leak types in the Leak Lab. Related: valve core leaks and using Bubble Check on TPMS, valve stem, and bead leaks. Questions: sales@chaosmoto.com or 480-829-7888.

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