BMW E81 E87 E90 E91 F01 F10 F20 F30 Radiator Expansion Tank Screw Cap 7639020

BMW E81 E87 E90 E91 F01 F10 F20 F30 Radiator Expansion Tank Screw Cap is an original cooling system component designed for a wide range of BMW models. Thanks to its factory design, it ensures proper sealing of the expansion tank and stable operating conditions for the coolant. This is a practical solution for users who want to maintain consistency with BMW factory specifications and avoid problems resulting from the use of low-quality replacements.

Specifications and technical data

• SKU: 7639020-1
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 7639020
• Substitutable numbers: 17117639020, 7639020, 17117521071, 7521071
• Category: Caps

Purpose and function of the BMW expansion tank cap

The presented cap is a cooling system component responsible for maintaining the tightness of the expansion tank and controlling operating pressure. A properly selected cap helps reduce the risk of engine overheating, coolant leaks, and improper operation of the entire system.

Its original BMW origin ensures that the opening pressure parameters, thread fit, and seals are matched to the factory tank and compatible with the cooling system design of the given vehicle generation.

Benefits of using an original BMW cap

Using a factory expansion tank cap in BMW E and F series models allows for maintaining stable engine operating conditions and reducing the risk of failures resulting from leaks. In practice, this means:

• better fit to the original expansion tank,
• maintenance of the pressure parameters specified by the manufacturer,
• reduction of the risk of uncontrolled coolant loss,
• easier diagnostics of potential cooling system faults.

For users who value consistency with the original BMW design, this is a solution that allows for maintaining predictable vehicle behavior under various operating conditions.

Product characteristics and fitment

The cap belongs to the group of components mounted on the expansion tank, acting as a safeguard for the cooling system against excessive pressure buildup. As a part from the Covers category, it is designed to work with the factory shape and geometry of the tank, which facilitates installation and ensures proper seating.

The product comes from the BMW range, which in practice translates into compliance with the factory quality standards applied by the vehicle manufacturer. This is particularly important for components that have a direct impact on the safety of engine operation and the durability of cooling system sub-assemblies.

Condition and service application

The offered cap is a used item, which makes it an attractive option for users looking for a service solution on a reasonable budget while maintaining the original origin of the part. It can be used both during routine cooling system maintenance and when replacing a damaged or worn cap in vehicles used on a daily basis.

Due to its factory origin, the cap will work well in workshops specializing in the BMW brand, as well as for users servicing their own cars who expect predictable installation and compatibility with the original expansion tank.

If you are planning a comprehensive repair or upgrade of the engine bay area in your BMW and need other elements from the same group, such as covers, caps, or additional trims, check out the available parts in the BMW Covers category.

Additional information and support in choosing parts

Selecting the right expansion tank cap is important for the proper operation of the cooling system, so before purchasing, it is worth verifying the compatibility of the part with the specific vehicle model and production year. Vehicle identification data and information contained in the product technical specification can be helpful.

If you want to better understand how to effectively choose original used components for popular car models and what to look for when purchasing, check out our guide: The best used car parts – a guide to the most frequently chosen original parts.