# 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.

- Type: Service bulletin
- NHTSA id: 11026950
- Published by NHTSA: 2026\-01\-05
- Manufacturer's number: B340925
- Manufacturer's date: 2025\-12\-17
- NHTSA component: SERVICE 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

- [NHTSA's copy of the document (PDF)](https://static.nhtsa.gov/odi/tsbs/2025/MC-11026950-0001.pdf)
- [If that address does not open, try this one](https://static.nhtsa.gov/odi/tsbs/2025/MC-11026950-9999.pdf)

The document is the manufacturer's. This site does not hold it.

## Components

Brakes

## Vehicles listed

- 2024 to 2026 BMW 330I
- 2024 to 2026 BMW 430I
- 2024 to 2026 BMW M3
- 2024 to 2026 BMW M4

## Other bulletins for the same vehicles and component

- [B340226](/bulletins/11036389.md), 2026-08-27, Service campaign: SERVICE BRAKES. 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.
- [B062826](/bulletins/11031899.md), 2026-05-01, Other: SERVICE BRAKES. Brake Hose Return
- [B340925](/bulletins/11021109.md), 2025-07-31, Service campaign: SERVICE BRAKES. 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.
- [B340625](/bulletins/11018518.md), 2025-05-21, Service bulletin: SERVICE BRAKES. 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](/bulletins/11017082.md), 2025-04-17, Service campaign: SERVICE BRAKES. 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 .
- [eB340225](/bulletins/11016435.md), 2025-04-03, Service campaign: SERVICE BRAKES. Delivery Stop \- Brake Fluid Expansion Tank
- [B340714](/bulletins/10244237.md), 2023-11-01, Service bulletin: SERVICE BRAKES, HYDRAULIC. Functional noises \(squealing/honking\) when braking shortly before the vehicle comes to a stop. CAUSE Material\-

JSON: [/v1/bulletins/11026950](/v1/bulletins/11026950)

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