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Service bulletin B340925

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

The communication, as NHTSA indexes it (as of 2026-10-19)
TypeService bulletin
NHTSA id11026950
Published by NHTSA2026-01-05
Manufacturer's numberB340925
Manufacturer's date2025-12-17
NHTSA componentSERVICE BRAKES

NHTSA's summary

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.

The document

The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Brakes

Vehicles listed
BMW 330I2024, 2025, 2026
BMW 430I2024, 2025, 2026
BMW M32024, 2025, 2026
BMW M42024, 2025, 2026

Listing a model year does not mean every vehicle of it is concerned: the document says which.

Other bulletins for the same vehicles and component
B3402262026-08-27. Service campaign. The protective film which covers the 6 threaded connection holes on the DSC hydro unit may not have been completely removed before the brake line was fastened. This can lead to a gradual loss of brake fluid at the threaded connection. As a result, the driver is alerted at an early stage by a red Check Control Message stating “Brake system defective. Stop carefully. Do not continue driving. Call BMW Roadside Assistance”. However, there is no functional limitation of the brake.
B0628262026-05-01. Other. Brake Hose Return
B3409252025-07-31. Service campaign. 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 level sensor might malfunction over a relatively long period of time.
B3406252025-05-21. Service bulletin. Brake “groaning” noises heard at the rear axle at slow speeds, i.e. close to standstill, stop and go driving;when parking or maneuvering.
B3402252025-04-17. Service campaign. 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, the filling level sensor might malfunction over a relatively long period oftime .
eB3402252025-04-03. Service campaign. Delivery Stop - Brake Fluid Expansion Tank
B3407142023-11-01. Service bulletin. Functional noises (squealing/honking) when braking shortly before the vehicle comes to a stop. CAUSE Material-