How Do I Replace The Valve Stem Gasket On A TST TPMS Cap Sensor?
Updated 10/02/2026 | Published 10/01/2026
Question:
How do I replace the small thick o-ring on the TST cap sensor. This is the one that seals the air pressure below the threads where it connects to the valve stem. Thanks.
asked by: Mark K
Expert Reply:
Hey Mark, thanks for reaching out. Yes, that small thick seal inside the threaded opening is the valve-stem gasket, which is different from the larger O-ring that seals the battery cap.
To replace it, remove the sensor from the valve stem and use a small pick or tiny flat screwdriver to carefully hook the old rubber gasket and pull it out of the bottom of the threaded opening. Be careful not to scratch the sealing surface. Press the new gasket straight down into that recessed seat until it lies flat, then thread the sensor back onto the valve stem until the air leak stops and give it about another 1/4 turn being careful not to over tighten.
What vehicle do you use the sensors on?
Product Page this Question was Asked From
Replacement O-ring Kit for TST SE2 Cap Sensors
- Accessories and Parts
- TPMS Sensor
- Tire Pressure Monitor Parts
- O-Ring
- TST
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on Accessories and Parts
Ray
10/2/2026
As someone who recently replaced the gaskets, batteries and O-rings on my RV trailer and truck sensor caps, after several years of intermittent use, I agree with everything in Jesse's comments. Most ESPECIALLY his comment about being careful not to scratch the brass sealing surface UNDER the gasket. With that I can attest to the fact that removing a gasket from the sensor cap is a bit tricky. It sits within a very narrow recession in the cap, with the pressure sensor stem sticking up through it, limiting access to the gasket. I found that the gasket tended to rotate around the sensor stem making it challenging get purchase on the gasket to lift it out. This sliding in place foiled my attempts to use a straight needle to tease the gasket up from its normal position without sticking the needle directly down which would risk striking the sealing surface underneath. I found success using a precision hooked pick to penetrate the gasket at angle, making sure to pushing against the side of the gasket chamber, not the bottom. Pushing the pick into the rubber gasket I got enough purchase to get part of it above the sensor stem. I then used a fine pair of forceps to pull the gasket out of the cap. By the time I was on my third sensor, things went quickly. Please note that using this method renders the old gasket unusable because of the hole created by the pick so only use it when a replacement is on hand. Overall, I have been very happy with my TST TPMS finding it to be very reliable and accurate.