BMW F20 F21 F30 F31 F32 F80 F82 Brake Master Cylinder Reservoir Tank Cap 6851090

The BMW F20 F21 F30 F31 F32 F80 F82 Brake Pump Reservoir Cap is an original brake system component from the servos and brake force regulators group, designed for selected BMW 1, 3, 4 Series, and M models. Designed as an OEM part, it ensures proper sealing of the brake fluid reservoir and stable operating conditions for the entire system, which translates to safe and predictable brake performance.

Specifications and technical data

• SKU: 6851090
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 6851090
• Substitutable numbers: 34336851090, 6851090
• Category: Brake Servos

Purpose and Role in the Braking System

The brake pump reservoir cap in BMW F20, F21, F30, F31, F32, F80, and F82 models is responsible for tightly sealing the brake fluid reservoir and stabilizing the pressure above the fluid level. A correctly selected component helps reduce the risk of moisture and contaminants entering the system, which is important for the durability of the pump, servo, and brake force regulator.

As a part from the Servos and Brake Force Regulators category, the cap works with other system components, supporting the maintenance of proper operating parameters during daily use as well as intensive braking.

Why Choose an Original BMW Cap

An original BMW brake pump reservoir cap is designed for the specific geometry of the reservoir and the characteristics of the braking system in a given platform. Thanks to this, it ensures:

• secure seating on the reservoir and proper sealing,
• compatibility with the factory servo and brake force regulator,
• maintenance of system operating parameters according to the manufacturer's specifications.

Selecting an OEM part is particularly important in high-performance cars, such as M versions, where the braking system operates under more demanding conditions. In such cases, component consistency directly impacts braking force repeatability and vehicle stability.

Part Characteristics and Condition

The offered cap comes from the BMW OE line, meaning it is a component that conforms to the vehicle manufacturer's factory specifications. The part is used, making it a cost-effective solution while maintaining proper fit for the braking system of the specific model.

For components like the brake pump reservoir cap, maintaining the correct sealing geometry and proper venting is crucial. Choosing an original part from a dismantled vehicle allows these parameters to be maintained at a level close to factory standards, without the need for replacements of uncertain quality.

Practical Installation and Maintenance Tips

Replacing the brake pump reservoir cap is one of the simpler service tasks, but it's worth combining it with a check of the brake fluid level and a visual inspection of the lines and the reservoir itself. During installation, pay attention to:

• cleanliness of the reservoir edges and the sealing seat,
• proper pressing of the cap until a noticeable click or lock is felt,
• absence of leaks after a short test drive.

For a comprehensive approach to vehicle system servicing, it is also worth consulting the guide on thermal comfort and parts selection, described in the entry Air Conditioning and Heating – Parts Selection and Maintenance for Year-Round Comfort, which organizes the approach to used OEM components in various vehicle systems.

BMW M, Braking System, and Parts Selection

The F80 and F82 versions belong to the BMW M family, where the braking system is more heavily loaded than in standard variants. In such cars, it is particularly important to use components that comply with factory specifications to maintain predictable vehicle behavior during high-speed braking. If you are interested in the broader context of differences between M and standard components, the article BMW M Performance – Differences Between BMW M and Standard Components, which discusses, among other things, the specifics of brakes and the rationale for using used BMW parts, may be helpful.

Summary

The BMW F20 F21 F30 F31 F32 F80 F82 Brake Pump Reservoir Cap is a factory brake system component designed for specific BMW F-series models. As a part from the servos and brake force regulators group, it supports the proper functioning of the entire system, ensuring a tight seal for the brake fluid reservoir and stable operating conditions. It is a sensible choice for users who want to maintain factory braking parameters while utilizing a proven, used OEM part.