Model S/X refresh (2021+): battery sealing issues (officially acknowledged by Tesla)

Honest disclaimer (important)

Since May 2025 the sealing of the refresh pack has been an issue officially acknowledged by Tesla: bulletin SB-25-16-002 (see below). As far as the breather valves go, though, this article is still an observation, not a confirmed case report. After checking the archive of the Russian-language Tesla chat RTC (450k+ messages) and TMC, we found:

• Zero first-hand valve repairs on refresh S/X in the Russian-speaking community. Only retellings from English-language forums and questions like "I heard there are problems, is it true?".
• BMS_w168 errors are not mentioned in the chat even once.
• BMS_a066 is mentioned, but only on Model 3, and it is read as a cell imbalance or a dead cell, not as a sealing problem.

So for the "breathing" failures this article stays a watch-out (what to look at when buying or diagnosing a car), and its severity has been lowered to 2 (normal) until real cases appear.

Where the rumours come from

Since 2023 a pattern has kept surfacing on TMC and in some YouTube reviews: the refresh S/X (with the ~100 kWh Palladium pack) are said to be, in theory, prone to the same breather valve defect as the old 85-kWh packs. The rubber seals stick, the pressure balance breaks during heating and cooling, and humid air may get drawn in.

Further indirect evidence:

• On the Cybertruck Tesla added active pressurisation of the battery housing with positive pressure (t.me/teslacar_chat/565042). That is an engineering admission that earlier generations had the problem.
• Owners asking about it directly in RTC: "I heard there are sealing problems with the main battery on the 2022+ Model S, is that true?" (t.me/teslacar_chat/505060, 2024-02), "the S Plaid supposedly had problems with the rubber vent valves" (t.me/teslacar_chat/574316, 2024-08), "the Plaid also has a screw-up with battery ventilation" (t.me/teslacar_chat/543336).
• An early warning in the chat in 2022-11 to owners of the 2022 S LR and Plaid about possible moisture ingress (t.me/teslacar_chat/255977).

Official acknowledgement: bulletin SB-25-16-002

In May 2025 the problem stopped being pure rumour. Tesla issued service bulletin SB-25-16-002 "Replace Flood Port Plungers" dated 05.05.2025. Under it, the 5 flood ports of the battery pack are replaced free of charge (goodwill) on Model S/X built 01.2021 to 22.09.2022 (US and Europe). Owners received "High Voltage Battery Seal" emails (TMC thread, Not a Tesla App write-up).

The caveat: the bulletin is about protection against external flooding (the flood ports), not about the valves "breathing" as the pack heats and cools. There are still no confirmed cases of moisture being drawn into Palladium packs that way.

If you want to play it safe when buying

• For cars built 01.2021–22.09.2022, check whether the SB-25-16-002 campaign (flood port replacement) has been done, by VIN at a service centre or from the service history. If it has not, the replacement is free (goodwill).
• When buying a used 2021–2023 refresh, ask for a pack pressure test as part of the PPI (pre-purchase inspection). The standard service test is ~0.19 psi.
• Check the BMS log in Service Mode for pressure swings across charge cycles.
• Inspect the valves on both sides of the pack from the outside (visually plus an airflow check) if the car is on a lift.

If the problem is already confirmed (the legacy 85 kWh path)

The procedure and costs come from confirmed cases on 85-kWh packs, where this is a real problem. If the same defect turns up on a refresh car, the expected repair would go like this:

1. Drop the pack (special tooling, a lift).
2. Replace the valves (the community calls them "umbrella valves") and the seals.
3. Clean and dry the pack if moisture is suspected.
4. Run the seal test again before reassembly.

A documented job on an 85-kWh pack (to give a sense of the budget): EV Clinic Berlin did "removal → cleaning → umbrella valve replacement → resealing" for 1450 euros (t.me/teslacar_chat/682998, July 2025).

Hypothetical budget in Belarus

• Valves, seals and labour only (if a real case ever appears): ≈ $800–1 500.
• With cleaning/drying plus replacement of damaged BMBs: ≈ $2 500–3 500.
• With deep module corrosion: up to $5 000.

(The figures are extrapolated from the 85-kWh cases; Belarusian shops have no confirmed price lists for the refresh yet.)

Why a bypass option won't exist

The Palladium pack is an integrated design: the housing, cooling and BMS are built in deeper than on the old 85. Home-made workarounds like the LDU bypass (where Tesla itself concluded that rotor cooling was unnecessary) will most likely not appear for the battery. Repairs go through a service centre.

What would update this article

• Real repair cases in the RU/BY community, with photos and prices.
• BMS_w168/a066 errors confirmed on the refresh cars specifically (not on Model 3).
• An extension of the SB-25-16-002 campaign (new VIN ranges) or an official recall from Tesla.

If you have had such a case on a refresh S/X, message @zverski on Telegram and we will update the article.

Links

• TMC: Tesla's "High Voltage Battery Seal" email to owners: https://teslamotorsclub.com/tmc/threads/high-voltage-battery-seal-email-from-tesla.344405/
• TMC: 2021 Model S / S Plaid refresh issues: https://teslamotorsclub.com/tmc/threads/2021-model-s-and-model-s-plaid-refresh-issues-thread.232656/
• Not a Tesla App: Tesla to replace battery seals on select Model S and Model X (SB-25-16-002): https://www.notateslaapp.com/news/2688/tesla-to-replace-battery-seals-on-select-model-s-and-model-x-vehicles
• Bulletin SB-25-16-002 "Replace Flood Port Plungers" (PDF, NHTSA mirror): https://static.oemdtc.com/NHTSA-PDFs/MC-11023640-0001.pdf
• An owner's direct question about MS 2022+ sealing: https://t.me/teslacar_chat/505060
• Rumours about the Plaid's rubber vent valves: https://t.me/teslacar_chat/574316
• A Plaid owner confirming the "ventilation screw-up": https://t.me/teslacar_chat/543336
• Cybertruck positive pressure as an engineering admission of the problem: https://t.me/teslacar_chat/565042
• EV Clinic Berlin: umbrella valve replacement on an 85 (1450 EUR): https://t.me/teslacar_chat/682998