BMW E87 E90 E92 Brake Master Cylinder Reservoir Cap Warning Switch 6774451

BMW E87 E90 E92 Brake Master Cylinder Reservoir Cap Warning Switch is an original brake system component from the Brake Servos and Proportioning Valves group, designed for use in BMW vehicles. It allows for the secure sealing of the brake fluid reservoir and integrates with the fluid level monitoring system, which is essential for stable brake operation and driving comfort.

Specifications and technical data

• SKU: 6774451-1
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 6774451
• Substitutable numbers: 34336774451, 6774451, 34326764119, 6764119, 34326752698, 6752698
• Category: Brake Servos

Function of the brake fluid reservoir cap with sensor

The presented cap is responsible for the airtight sealing of the brake fluid reservoir, and the integrated level sensor works with the vehicle's electrical system. This allows the brake system to signal a drop in fluid level on the instrument cluster, facilitating quick service response and reducing the risk of the system operating with an insufficient amount of working fluid. The component from this group is important for:

• maintaining the proper seal of the brake fluid reservoir,
• correct operation of the fluid level warning system,
• stable operation of the brake servo and proportioning valve under typical road conditions.

Compatibility with the BMW brake system

The cap was designed as an original BMW part, which ensures a proper fit for the brake fluid reservoir used in E87, E90, and E92 series models. Using a component from the same design group as the factory-installed one facilitates installation and helps maintain consistency with other brake system components. The original BMW OE origin means that the geometry, mounting method, and electrical connector of the sensor are adapted to the factory vehicle installation, which reduces the need for modifications and speeds up service work.

Characteristics of the used component

The offered brake fluid reservoir cap with sensor comes from disassembly and is classified as a used part. Such components are frequently chosen by professional workshops and individual users who are looking for a reasonable compromise between repair costs and maintaining the original brake system specifications. In the case of components from the Brake Servos and Proportioning Valves group, it is essential that the cap with the sensor ensures correct cooperation with the existing reservoir and electrical system – using an original component from disassembly promotes this compatibility.

Practical installation and maintenance tips

When replacing the brake fluid reservoir cap with sensor, it is worth paying attention to:

• the condition of the reservoir socket and the seal,
• the cleanliness of the contact surfaces to avoid introducing contaminants into the brake fluid,
• the correct connection of the fluid level sensor electrical connector. To better utilize the potential of parts from disassembly and keep them in good condition, it is worth reading practical maintenance advice – you will find it in the article How to extend the life of used car parts?, which describes proven ways to care for components sourced from disassembly.

Expanding the BMW brake system

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

Summary

BMW E87 E90 E92 Brake Master Cylinder Reservoir Cap Warning Switch is a practical solution for users and service centers that want to maintain the original brake system configuration in BMW vehicles. Its original origin, fitment to the factory reservoir, and integration with the fluid level warning system make it a functional choice for repairs and upgrades of the braking zone.