BMW bulletin B340925
What it saysThere may be an internal leakage in the brake fluid expansion tank (aka brake fluid reservoir). NHTSA’s full summary ↓
BMW filed this with NHTSA as a service bulletin dated Dec 17, 2025, received Jan 5, 2026, about the service brakes. It names 9 model years (2024–2026). A service bulletin is not a safety recall: it is the manufacturer telling its dealers how to diagnose or repair a condition, and whether the work is paid for depends on the warranty in force. Quoting the number at a service desk can save a diagnosis.
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What the bulletin says
Source: NHTSA's summary of the manufacturer's communicationThere 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.
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| B340925 | Service bulletin | Dec 17, 2025 | 11026950 | PDF, 248 KB |
What the document itself lists
Parts the bulletin names
| Part number | Description | Qty | Find it |
|---|---|---|---|
| 34 51 9 504 021 | Expansion tank | 1 | eBay Motors → |
| 07 11 9 905 147 | Hex bolt with washer (M10x25-10.9ZNS3) | 4 | eBay Motors → |
| 07 14 7 483 888 | Hex bolt | 4 | eBay Motors → |
| 07 14 8 086 257 | Hex bolt (M10x35) | 4 | eBay Motors → |
| 07 14 9 502 134 | Multi-purpose bolt | 2 | eBay Motors → |
| 51 61 8 084 883 | Hex bolt (M10x70) | 4 | eBay Motors → |
Labour operation and the time the manufacturer allows
| Operation | Description | Time |
|---|---|---|
| 00 78 713 | Additional work with fixed caliper for inaccessible rim designs | 2 FRU |
Read by machine from the document NHTSA serves (5 pages), read Sep 30, 2026. A part number is shown only where it matches BMW’s own catalogue shape, an operation only with its code and time, and a description only where the reader got it whole; anything it could not settle is left out, and the PDF is the record. Times are the manufacturer’s warranty allowances, not a quote. Listings and prices on eBay Motors are the seller’s.
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The summary is NHTSA’s abstract of the document, as filed under 49 CFR 579.5. One communication is usually filed as several documents — the bulletin, a dealer notice, an owner letter — and the number on any of them finds this page. A PDF link is shown only once NHTSA’s own server has been seen to serve that document; the rest are checked over the following nights. Quote the number at a service desk; it is what the dealer’s system is keyed on.
Model years it names
Source: as the manufacturer filed themA vehicle page’s bulletin list shows the newest few communications filed against that model year; the count there is every one.
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What owners reported
Source: NHTSA complaint databaseOwners of the 9 model years this bulletin names have filed 37 complaints with NHTSA since 2015. 6 of them name Service Brakes — the same broad component group this bulletin is filed under. NHTSA groups complaints coarsely, so that means the same area of the vehicle, not necessarily the same fault.
Before the collision, my 2025 BMW 330i stalled when I tried to accelerate, so I moved into the right slow lane. The vehicle also stalled during the collision. My VIN lookup shows an unrepaired recall involving the starter-generator. I do not know whether the recall issue caused the stalling.
2025 BMW 3 Series · Service Brakes · filed with NHTSA Oct 6, 2026 · ODI 11769218
We were driving on a local road and saw the car ahead parked at the traffic light. We began to brake from a safe distance. The car began slowing but instead of coming to a full stop, the brake resisted, the car made an odd sound, and instead the car accelerated into the car in front of us.
2025 BMW 4 Series · Service Brakes · filed with NHTSA Sep 29, 2025 · ODI 11690335
Yesterday 4pm try to park my car at infront of grage door i have been slow down with touch break pedal. But this car won't stop at all so this car hit home grage door and and side stone decorations
2024 BMW 3 Series · Service Brakes · filed with NHTSA Nov 19, 2025 · ODI 11700260
A complaint is one owner’s account, not a defect finding, and a bulletin is not a recall. Nothing here says this bulletin was issued because of these complaints, or that the repair it describes fixed them. Complaint files on this site begin in 2015.
More bulletins about the service brakes
Source: same model, same component group12 other manufacturer communications filed against these BMW models under the same component group (service brakes), newest first. The eight newest are listed; the rest are on the BMW list.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| 0034410300 | Service campaign | Aug 27, 2026 | The protective film which covers the 6 threaded connection holes on the DSC hydro unit may not have been completely removed before the brake… |
| B320426 | Service campaign | Jul 23, 2026 | Hydro Unit DSC |
| B062826 | Other | Apr 24, 2026 | Brake Hose Return |
| B064725 | Other | Sep 9, 2025 | Protection Plate Return |
| 0034200300 | Service campaign | Jul 30, 2025 | There may be an internal leakage in the brake fluid expansion tank (aka brake fluid reservoir). In the rare case of a leak, the filling leve… |
| B341025 | Service bulletin | Jul 14, 2025 | After programming from the I-Levels between …24-03-505 and lower than …24-03-540 to I-Level …24-11-530 or higher, the following CCM may be d… |
| B340625 | Service bulletin | May 2, 2025 | Brake “groaning” noises heard at the rear axle at slow speeds, i.e. close to standstill, stop and go driving;when parking or maneuvering. |
| B340225 | Service campaign | Apr 3, 2025 | Due to a manufacturing defect, there might be an internal leakage of the brake fluid expansion tank. In therare case that there is a leakage… |
Quote the number at the service desk. It is what the dealer’s system is keyed on.
Every manufacturer communication NHTSA holds for BMW, by the number printed on the letter.
Common questions
Source: NHTSA, 49 CFR 579.5Is BMW B340925 a recall?
No. A service bulletin is a manufacturer communication filed with NHTSA under 49 CFR 579.5; a safety recall carries an NHTSA campaign number (two digits, a letter, six digits) and a federal duty to repair for free. Check the vehicle’s recalls by VIN at nhtsa.gov/recalls, or on its page here.
Is the B340925 repair free?
Not automatically. A service bulletin describes how to diagnose or repair a condition; who pays depends on the warranty in force, any extension, and the dealer. Quoting the number can save a diagnosis either way. Every BMW warranty extension on file lists the ones BMW has filed.
Which vehicles does B340925 cover?
The manufacturer filed it against 9 model years: 2026 BMW 3 Series, 2025 BMW 3 Series, 2024 BMW 3 Series, 2026 BMW 4 Series, 2025 BMW 4 Series, 2024 BMW 4 Series and more. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone.