Heavy Duty Coolant Expansion Tank Cap For Audi A4 A5 A6 A7 A8L S4 S5 Q5 Q7 Q8 RS4 RS5 VW Touareg Porsche Direct Fit Replacement Surge Tank Cap 4M0121321J 4M0121321K

Heavy Duty Coolant Expansion Tank Cap for Audi/VW direct fit
✔️ Direct fit replacement cap compatible with 4M0121321J/K variants

This heavy-duty coolant expansion tank cap is a direct replacement option for Audi, VW, and Porsche cooling systems. It seals the radiator surge tank to maintain proper pressure and prevent coolant leaks. It’s compatible with models like the Audi A4, A5, Q5, Q7, Q8, RS4/RS5, VW Touareg, and Porsche vehicles listed in the fitment notes.

✅ Compatible with Audi A4/A5/A6/A7/A8L, Q5/Q7/Q8, RS4/RS5 and VW Touareg
✅ Direct replacement with 4M0121321J/K compatibility
✅ Premium materials and tested durability for long life
✅ Easy installation with direct-fit design

💡 What is the purpose of a cooling system expansion tank cap and why should I replace it?

A handy explanation: it seals the reservoir under pressure to keep coolant from spilling and to prevent air from entering the system. - direct fit for Audi and VW models - maintains proper cooling system pressure to prevent boil-over - compatible with part numbers like 4M0121321J and 4M0121321K