BMW bulletin B640326
What it saysAfter starting up the vehicle, a distinct, constant, “humming” noise can be heard from the right area of the instrument panel. NHTSA’s full summary ↓
BMW filed this with NHTSA as a service bulletin dated May 7, 2026, received May 18, 2026, about the engine. It names 1 model year (2025). 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 communicationWhat it applies to, as the document itself states it — the build window in the manufacturer’s own words, read by machine from the PDF NHTSA serves. The build date is on the certification label in the driver’s door jamb; the dealer settles a borderline vehicle by its VIN.
After starting up the vehicle, a distinct, constant, “humming” noise can be heard from the right area of the instrument panel.
Document filed under this number
| Document | Kind | Dated | NHTSA id | At NHTSA |
|---|---|---|---|---|
| B640326 | Service bulletin | May 7, 2026 | 11032742 | PDF, 309 KB |
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 1 model year this bulletin names have filed 13 complaints with NHTSA since 2015.
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 engine
Source: same model, same component group5 other manufacturer communications filed against the BMW iX under the same component group (engine), newest first.
| Number | Kind | Dated | NHTSA’s summary |
|---|---|---|---|
| B170124 | Service bulletin | Feb 25, 2026 | There is coolant leaking from under the car Low heater output Possible Check Control message “Drive, you can continue driving” (ID49) Pos… |
| 0064340200 | Service campaign | Dec 9, 2024 | Quality checks have determined that the coolant changeover valve may develop a coolant leak under verylow outside temperatures… |
| 0064290200 | Service campaign | Jul 11, 2024 | Quality checks have determined that the coolant changeover valve may develop a coolant leak under very low outside temperatures… |
| B640724 | Service campaign | May 24, 2024 | Quality checks have determined that the coolant changeover valve may develop a coolant leak under ver ylow outside temperatures… |
| B640324 | Service bulletin | May 23, 2024 | The coolant changeover valve may develop a coolant leak when the outside temperatures go below 19°F (-7°C). The vehicles operating systems… |
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 B640326 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 B640326 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 B640326 cover?
The manufacturer filed it against 1 model year: 2025 BMW iX. Whether one particular vehicle is affected is a matter of its VIN and its build, not its model year alone. The document itself sets the build window: built on or after 1 Mar 2025 — the build date is on the certification label in the driver’s door jamb.