Window Guide BMW F01 F04 Rear Left N/S Door Side Window Sealing Gasket 7178021

Window Guide BMW F01 F04 Rear Left N/S Door Side Window Sealing Gasket is an original component from the Window seals and trims group, designed for installation in the rear left section of the vehicle body. It ensures a tight fit for the door window, reduces wind noise, and supports the proper operation of the window lifting mechanism, which translates into acoustic comfort and protection of the interior against moisture.

Specifications and technical data

• SKU: 7178021
• Mark: BMW (Genuine OE)
• Condition: Used
• OEM Part Number: 7178021
• Substitutable numbers: 51357178021, 7178021, 51354445355, 4445355, BG
• Location on the vehicle: Rear, Left
• Category: Window Seals, Gaskets & Trims

Purpose and function of the gasket

The presented gasket is dedicated to the rear left door window in BMW F01/F04 series models. Its placement in the rear door area means the component is responsible for guiding the window in the track, stabilizing its position, and maintaining a seal between the glass and the door frame.

Thanks to its proper profile, the rubber prevents water, dust, and contaminants from entering the door interior and the cabin, and also reduces wind noise at higher speeds. A correctly selected gasket also contributes to even window closing and reduces the load on the window regulator mechanism.

Benefits of using an original BMW gasket

Using an original gasket in the rear left body area allows for maintaining factory fitment and predictable window behavior during operation. The design, matched to the specific geometry of the door, minimizes the risk of leaks, rattling, or the glass rubbing against the frame.

Key advantages include:

• Precise fit to the door frame shape – no need for modifications or trimming.
• Stable window guidance throughout its entire range of motion.
• Reduction of cabin noise and improvement of acoustic comfort.
• Better protection of the door interior against moisture, which promotes the durability of mechanisms and electrical installations.

Installation characteristics and condition of the item

The gasket is designed for installation at factory mounting points in the rear left part of the body. By maintaining the original geometry, it is possible to restore the factory line of the window's contact with the door frame, which facilitates service work and shortens replacement time.

The product is in used condition, meaning it comes from disassembly and may show signs of wear typical for this type of part. It is a cost-effective solution, especially for repairs of daily-driven vehicles where functionality, fitment, and a reasonable service budget are important.

Application in the rear left body area

The placement of the gasket in the rear left door area is important both for passenger comfort and for protecting the vehicle's interior. A correctly selected component:

• ensures even pressure of the window against the frame,
• limits drafts and local leaks,
• supports maintaining the proper microclimate in the rear part of the cabin.

For BMW F01/F04 series users, this is an essential component for any work related to window replacement, door repair after a collision, or resolving issues with noise and leaks.

Related components and technical knowledge

If you are planning a comprehensive repair or upgrade of the window and door area in your BMW and need other components from the same group, such as additional gaskets, trim strips, or window guides, check the available parts in the BMW Window seals and trims category.

For those analyzing the cost-effectiveness of repairs and operation of cars of this brand, the material comparing popular BMW diesel engines may also be helpful – a detailed summary of performance, reliability, and parts costs can be found in the article BMW N47 vs M57 / M57N / M57N2 – ranking of legendary diesels.