Refresh your engine bay with the MMR Performance aluminium 90 mm coolant expansion and header tank cap for selected BMW and MINI models. Precision machined in the UK from a single piece of aluminium, this premium reservoir cap is a direct replacement for vehicles using OE reference 17 11 7 639 021, also written 17117639021.
- Solid aluminium construction for a durable, high quality finish
- Direct fit replacement for OE 17 11 7 639 021 / 17117639021
- 90 mm diameter for correct seating on the expansion system
- UK machined MMR Performance part with a clean, motorsport inspired look
- Complete replacement cap, not a stick on cover
Ideal as an aftermarket upgrade or replacement coolant reservoir cap, this header tank lid delivers an OEM style fit with a smarter, performance led appearance. If you are searching for a radiator cap, expansion tank cap, coolant reservoir cap, engine coolant bottle top or 90 mm header tank cap for BMW or MINI using the above OE reference, this is the part you need. Nforcd knows this product well and it has been popular with customers for its reassuring quality and neat fitment.
Verified fitment reference: 17 11 7 639 021 / 17117639021. Please check your existing cap for the OE number before ordering.
Need it fitted? Nforcd offers professional installation in Warwickshire. Request a quote at Sales@nforcd.com.





