This genuine part is produced in Audi auto parts factory, so we guarantee high quality spare accessories that is affordable, reliable and built to last on Audi cars. EuroPartsGiant.com is your prime online source with the biggest and best selection of genuine OEM Audi parts and accessories at giant discounted prices. We have all Audi parts and accessories you need at the wholesale prices. EuroPartsGiant.com has you covered no matter what type of Audi vehicle you drive.
- Brand:

- SKU: 4M0-121-321-Q
- Other Names: Radiator Cap, Reservoir Cap, Engine Coolant Reservoir Cap
- Description:
Expansion tank cap. A4. Reservoir cap. A5. To 06/15/20.
- Notes: Included with reservoir tank.
- Applications: 2.9L, 3.0L. 4.0L COOLING SYSTEM. 3.0L MAIN COOLING SYSTEM.
- Replaces: 4M0-121-321-H, 4M0-121-321-J, 4M0-121-321-K
- Sold In Quantity: 1
Vehicle Fitment
| Year | Make | Model | Body & Trim | Engine & Transmission |
|---|---|---|---|---|
| 2024 | Audi | A6 allroad | Premium Plus, Prestige | 3.0L V6 – Electric/Gas |
| 2024 | Audi | Q5 | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas |
| 2024 | Audi | Q5 PHEV | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas |
| 2024 | Audi | RS5 | Base | 2.9L V6 – Gas |
| 2024 | Audi | RS5 Sportback | Base | 2.9L V6 – Gas |
| 2024 | Audi | RS6 Avant | Performance | 4.0L V8 – Electric/Gas |
| 2024 | Audi | RS7 Sportback | Performance | 4.0L V8 – Electric/Gas |
| 2024 | Audi | S4 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2024 | Audi | S5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2024 | Audi | S5 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2024 | Audi | SQ5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2023 | Audi | A5 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas |
| 2023 | Audi | A5 Sportback | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas |
| 2023 | Audi | A6 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV), 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | A6 allroad | Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | A7 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | A8 Quattro | L | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | Q5 | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | Q5 PHEV | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – PLUG-IN HYBRID EV-GAS (PH |
| 2023 | Audi | Q7 | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV), 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | Q8 | Premium, Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | RS Q8 | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | RS5 | Base | 2.9L V6 – Gas |
| 2023 | Audi | RS5 Sportback | Base | 2.9L V6 – Gas |
| 2023 | Audi | RS6 Avant | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | RS7 Sportback | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | S4 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2023 | Audi | S5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2023 | Audi | S5 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2023 | Audi | S6 | Premium, Premium Plus, Prestige | 2.9L V6 – Electric/Gas, 2.9L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | S7 Sportback | Premium, Premium Plus, Prestige | 2.9L V6 – Electric/Gas, 2.9L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | S8 | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | SQ5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2023 | Audi | SQ5 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2023 | Audi | SQ7 | Premium Plus, Prestige | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2023 | Audi | SQ8 | Premium Plus, Prestige | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | A5 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas |
| 2022 | Audi | A5 Sportback | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | A6 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV), 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | A6 allroad | Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | A7 Sportback | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – PLUG-IN HYBRID EV-GAS (PH, 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | A8 Quattro | L | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV), 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | Q5 | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | Q5 PHEV | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – PLUG-IN HYBRID EV-GAS (PH |
| 2022 | Audi | Q7 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas, 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | Q8 | Premium, Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | RS Q8 | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | RS5 | Base | 2.9L V6 – Gas |
| 2022 | Audi | RS5 Sportback | Base | 2.9L V6 – Gas |
| 2022 | Audi | RS6 Avant | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | RS7 Sportback | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | S4 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2022 | Audi | S5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2022 | Audi | S5 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2022 | Audi | S6 | Premium Plus, Prestige | 2.9L V6 – Electric/Gas, 2.9L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | S7 Sportback | Premium Plus, Prestige | 2.9L V6 – Electric/Gas, 2.9L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | S8 | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | SQ5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2022 | Audi | SQ5 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2022 | Audi | SQ7 | Premium Plus, Prestige | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2022 | Audi | SQ8 | Premium Plus, Prestige | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | A4 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | A5 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | A5 Sportback | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | A6 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV), 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | A6 allroad | Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | A7 Sportback | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – PLUG-IN HYBRID EV-GAS (PH, 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | A8 Quattro | L, L Plug-In Hybrid | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV), 3.0L V6 – PLUG-IN HYBRID EV-GAS (PH, 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | Q5 | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | Q5 PHEV | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – PLUG-IN HYBRID EV-GAS (PH |
| 2021 | Audi | Q7 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas, 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | Q8 | Premium, Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | RS Q8 | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | RS5 | Base | 2.9L V6 – Gas |
| 2021 | Audi | RS5 Sportback | Base | 2.9L V6 – Gas |
| 2021 | Audi | RS6 Avant | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | RS7 Sportback | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | S4 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2021 | Audi | S5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2021 | Audi | S5 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2021 | Audi | S6 | Premium Plus, Prestige | 2.9L V6 – Electric/Gas, 2.9L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | S7 Sportback | Premium Plus, Prestige | 2.9L V6 – Electric/Gas, 2.9L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | S8 | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | SQ5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2021 | Audi | SQ5 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2021 | Audi | SQ7 | Premium Plus, Prestige | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2021 | Audi | SQ8 | Premium Plus, Prestige | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | A4 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2020 | Audi | A4 Quattro | Premium, Premium Plus, Prestige, Ultra sport | 2.0L L4 – Gas |
| 2020 | Audi | A4 allroad | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2020 | Audi | A5 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2020 | Audi | A5 Sportback | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2020 | Audi | A6 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Gas, 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | A6 allroad | Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | A7 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | A8 Quattro | L, L Plug-In Hybrid | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV), 3.0L V6 – PLUG-IN HYBRID EV-GAS (PH, 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | Q5 | Premium, Premium Plus, Prestige, Titanium Premium, Titanium Premium Plus, Titanium Prestige | 2.0L L4 – Gas |
| 2020 | Audi | Q5 PHEV | Premium, Premium Plus, Prestige | 2.0L L4 – Electric/Gas, 2.0L L4 – PLUG-IN HYBRID EV-GAS (PH |
| 2020 | Audi | Q7 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas, 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | Q8 | Premium, Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | RS Q8 | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | S4 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2020 | Audi | S5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2020 | Audi | S5 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2020 | Audi | S6 | Premium Plus, Prestige | 2.9L V6 – Electric/Gas, 2.9L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | S7 Sportback | Premium Plus, Prestige | 2.9L V6 – Electric/Gas, 2.9L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | S8 | Base | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | SQ5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2020 | Audi | SQ7 | Premium Plus, Prestige | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2020 | Audi | SQ8 | Premium Plus, Prestige | 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2019 | Audi | A4 | Premium, Premium Plus, Prestige, Titanium | 2.0L L4 – Gas |
| 2019 | Audi | A4 Quattro | Premium, Premium Plus, Prestige, Ultra sport | 2.0L L4 – Gas |
| 2019 | Audi | A4 allroad | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2019 | Audi | A5 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2019 | Audi | A5 Sportback | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2019 | Audi | A6 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Gas, 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2019 | Audi | A7 Sportback | Premium, Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2019 | Audi | A8 Quattro | L | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV), 4.0L V8 – Electric/Gas, 4.0L V8 – MILD HYBRID EV-GAS (MHEV) |
| 2019 | Audi | Q5 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2019 | Audi | Q7 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas, 3.0L V6 – Gas |
| 2019 | Audi | Q8 | Premium, Premium Plus, Prestige | 3.0L V6 – Electric/Gas, 3.0L V6 – MILD HYBRID EV-GAS (MHEV) |
| 2019 | Audi | RS5 | Base | 2.9L V6 – Gas |
| 2019 | Audi | RS5 Sportback | Base | 2.9L V6 – Gas |
| 2019 | Audi | S4 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2019 | Audi | S5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2019 | Audi | S5 Sportback | Premium Plus, Prestige | 3.0L V6 – Gas |
| 2019 | Audi | SQ5 | Premium, Premium Plus, Prestige | 3.0L V6 – Gas |
| 2018 | Audi | A4 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2018 | Audi | A4 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2018 | Audi | A4 allroad | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2018 | Audi | A5 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2018 | Audi | A5 Sportback | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2018 | Audi | Q5 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2018 | Audi | Q7 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas, 3.0L V6 – Gas |
| 2018 | Audi | RS5 | Base | 2.9L V6 – Gas |
| 2018 | Audi | S4 | Premium Plus, Prestige | 3.0L V6 – Gas |
| 2018 | Audi | S5 | Premium Plus, Prestige | 3.0L V6 – Gas |
| 2018 | Audi | S5 Sportback | Premium Plus, Prestige | 3.0L V6 – Gas |
| 2018 | Audi | SQ5 | Premium Plus, Prestige | 3.0L V6 – Gas |
| 2017 | Audi | A4 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2017 | Audi | A4 Quattro | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2017 | Audi | A4 allroad | Premium, Premium Plus, Prestige | 2.0L L4 – Gas |
| 2017 | Audi | Q7 | Premium, Premium Plus, Prestige | 2.0L L4 – Gas, 3.0L V6 – Gas |
Warranty: This genuine Cap Audi 4M0121321Q is guaranteed by Audi’s Factory warranty.
Shipping & Return: Shipping Policy, Return Policy.


