BMW 1 3 Series E81 E82 E87 E90 E91 E92 E93 Expansion Tank Brake Fluid Reservoir

BMW 1 3 Series E81 E82 E87 E90 E91 E92 E93 Expansion Tank Brake Fluid Reservoir is an original brake system component designed for 3 Series models, which works in conjunction with the Brake Servos and Proportioning Valves system. This used OEM reservoir ensures proper brake fluid storage and stable supply to the master cylinder and servo, resulting in predictable brake pedal performance. It is a practical solution for BMW owners who want to maintain factory braking characteristics while keeping repair costs reasonable.

Specifications and technical data

• SKU: 6764117
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 6764117
• Substitutable numbers: 34326764117, 6764117
• Category: Brake Servos

Purpose and function in the brake system

The presented brake fluid reservoir is a component that works with the servo and brake proportioning valve in the BMW 3 Series E90/E91 generation. Its task is to safely store brake fluid and ensure an adequate level of the working medium for the entire system. Thanks to the factory OEM design, proper connection geometry and fitment to the master cylinder and fluid level sensors are maintained.

A properly selected reservoir minimizes the risk of air entering the system, facilitates bleeding after service, and supports the stable operation of the servo and proportioning valve. This is particularly important in daily use, where a predictable vehicle response to brake pedal pressure is essential.

Benefits of using an original BMW reservoir

Using an original reservoir from a dismantled BMW E90/E91 allows you to maintain the factory operating parameters of the brake system. The component was designed specifically for this model, which means:

• a secure fit to the master cylinder and servo,
• compatibility with factory mounts and brackets in the engine bay,
• proper positioning of the ports for brake lines and venting,
• compatibility with original fluid level sensors.

A used OEM component is a reasonable compromise between cost and quality – it allows you to maintain the integrity of the entire brake system without the need to use aftermarket replacements with uncertain parameters.

Condition, origin, and practical application

The offered reservoir comes from a dismantled BMW vehicle, which guarantees its structural fit for the 3 Series E90/E91. As a used part, it is intended primarily for:

• accident repairs within the engine bay,
• removing leaks or damage to an existing reservoir,
• restoring proper system operation after work on the servo or brake proportioning valve.

Choosing this solution is particularly beneficial when you want to maintain the original vehicle specification and compatibility with factory components, without interfering with the brake system design.

Integration with the Brake Servos and Proportioning Valves system

As a component in the Brake Servos and Proportioning Valves category, the brake fluid reservoir plays an important role in the entire hydraulic circuit. Proper interaction with the servo and proportioning valve affects:

• stable brake assistance under various load conditions,
• even distribution of braking force between axles,
• maintenance of proper operating pressure in the system.

By maintaining the original geometry and capacity of the reservoir, it is possible to keep braking characteristics consistent with the manufacturer's specifications, which is important for both safety and driving comfort.

Technical support and additional information

When selecting used OEM components for the brake system, it is worth paying attention to compatibility with the specific body version and brake system of your BMW. If necessary, you can refer to the manufacturer's markings and interchangeable part numbers visible in the product technical specification to ensure that the reservoir will be suitable for your configuration.

If you are planning a comprehensive repair or upgrade of the braking zone in your BMW and need other components from the same group, such as a brake servo, proportioning valve, or related mounting elements, check out the available parts in the BMW Brake Servos and Proportioning Valves category.

During service work in the engine bay and brake system, it is also worth taking care of the efficiency of systems responsible for driving comfort. In this regard, our blog guide will be helpful: Air conditioning and heating – part selection and maintenance for year-round comfort, where you will find practical tips on selecting used OEM components and service schedules.

If you are interested in the broader context of using dismantled parts and want to better understand how they affect operating costs and the environment, take a look at the article Circular economy in your garage – how choosing used dismantled parts really supports environmental protection and your wallet?, which discusses the practical aspects of using used components in modern cars.