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SIB 34 09 25: Coolant expansion tank leak
Coolant expansion tank leak on BMW G20/G22/G23/G26 and other models (2024–2026); BMW explains the cause and the approved repair.
BMW service bulletin · NHTSA ID 11026950 · Dec 2025 · also written SI B34 09 25, B340925
What it covers
A service bulletin tells BMW technicians how to diagnose or fix a known issue. It is not a recall: a repair under a bulletin is normally paid by the owner unless the car is still under warranty or a warranty extension applies.
There may be an internal leakage in the brake fluid expansion tank (aka brake fluid reservoir). In the rarecase of a leak, the filling level sensor might malfunction over a relatively long period of time.
Details
| Bulletin number | SIB 34 09 25 Also written: SI B34 09 25, B340925, 34 09 25, SIB-34-09-25, SI B340925 |
|---|---|
| NHTSA ID | 11021109, 11026950 (revisions) |
| Document IDs filed | B340925 |
| Type | Service bulletin |
| Date | (first filed Jul 2025) |
| Models | 330i, 430i, M2, M3, M4 |
| Model years | 2024–2026 |
| Chassis | G20, G22, G23, G26, G80, G81, G82, G83, G87 |
| Engines | B46/B48, S58 |
| Component (NHTSA) | Service Brakes |
Model, year and engine coverage comes from NHTSA's records. Not every car in this range is affected; the official document lists the exact production dates and conditions.
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Related bulletins
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- SIB 34 02 26 Brakes warning message Brakes warning message on BMW G22/G23/G26 models (2026); BMW gives an inspection and repair procedure. Service campaign · Aug 2026
- NHTSA 11016435 Coolant expansion tank new-car delivery hold Coolant expansion tank new-car delivery hold on BMW G20/G22/G23/G26 and other models (2025); unsold cars were held for inspection and repair before delivery. Service campaign · Mar 2025
- SIB 34 02 25 Coolant expansion tank leak Coolant expansion tank leak on BMW G20/G22/G23/G26 and other models (2025); BMW repairs affected cars free under a service campaign. Service campaign · Apr 2025
- SIB 34 09 21 Axle noise Axle noise on BMW F80/F82/F83/G80 and other models (2015–2022); BMW explains the cause and the approved repair. Service bulletin · Jan 2025
- SIB 34 05 17 Brakes ticking noise Brakes ticking noise on BMW G01/G02/G05/G06 and other models (2010–2021); BMW explains the cause and the approved repair. Service bulletin · Jul 2020
Before you pay: check your VIN for recalls
Some failures are covered by a safety recall or a warranty extension. Our free recall check lists NHTSA recalls for your car's model and year.
Source: NHTSA Manufacturer Communications (public data). BimmerBench is not affiliated with BMW or NHTSA. The title and description above are our own plain-English summary; the full bulletin is BMW's document, linked above.