MMX Performance BMW Billet Coolant Expansion Cap
Description
The MMX Performance BMW Billet Coolant Expansion Cap is a precision-engineered upgrade designed to improve both the durability and appearance of your BMW’s cooling system. Unlike decorative covers, this is a true OE replacement cap that fully replaces the factory plastic unit while retaining complete factory functionality.
Factory coolant caps are constructed from plastic and can degrade over time due to repeated heat cycles, leading to potential sealing issues and reduced confidence during servicing. The MMX billet cap addresses this with a robust construction machined from a solid block of 6061 aerospace-grade aluminum, offering superior strength, heat resistance, and long-term reliability.
Each cap is CNC-machined using advanced 5-axis technology, then finished in a deep gloss black anodizing for a clean OEM+ appearance and excellent corrosion resistance. The carefully machined exterior provides improved grip, allowing for confident installation and removal during coolant servicing.
Pre-installed with OE-spec internals including a pressure valve, internal spring, and Viton O-ring seal, the MMX coolant expansion cap ensures proper pressure regulation and sealing performance without requiring any transfer of components from the factory cap. This makes installation simple and fully plug-and-play.
Available in both 60mm and 90mm fitments, this billet coolant cap replaces BMW OE part numbers 17117639024 (60mm) and 17117639021 (90mm). Please confirm the part number on the underside of your existing cap to ensure correct fitment.
A functional and aesthetic upgrade, the MMX Performance BMW Billet Coolant Expansion Cap delivers long-term reliability while adding a refined finishing touch to any engine bay.
Product Details
- MMX Performance billet coolant expansion cap for BMW
- Available in 60mm and 90mm fitments
- Replaces OE part numbers 17117639024 (60mm) and 17117639021 (90mm)
- Direct OE replacement with full factory-style internals
- Pre-installed pressure valve, internal spring, and Viton O-ring seal
- CNC-machined from 6061 aerospace-grade aluminum
- Advanced 5-axis machining for precise fitment
- Gloss black anodized finish for corrosion resistance and OEM+ appearance
- Improved grip design for easier installation and removal
- Eliminates concerns associated with aging plastic caps
Vehicle Applications
- BMW models equipped with matching OE coolant cap part numbers
Recommended Products
Notes
- SKU: MMR03-1502 (90mm), MMR03-1503 (60mm)
- Designed and engineered in the UK
- Direct OE replacement – no modifications required
- Verify cap size or OE part number prior to purchase
- Prolonged exposure to extreme heat may affect anodized finish appearance
- This does not impact performance or functionality
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