If you're looking to modify, upgrade, or simply keep up with the maintenance on an Audi B5 S4, upgrading the cooling system with new CSF's high-performance all-aluminum radiator is highly recommended. It's another crucial fix along with a laundry list of other items to replace and maintain on the iconic Audi B5 S4. Keep in mind that these cars are over 20 years old, and if you haven't already had to replace your original plastic tank radiator, the time is definitely coming soon.
Introduced all the way back in 1997, the Audi B5 S4 came stock with a 2.7L twin-turbo V6 engine pushing out a baseline of 250 hp and 258 lb-ft torque. A simple tune and a few basic bolt-on parts can easily add on 100 hp to one of Audi's most iconic sports cars that have become a favorite for track guys. The B5 S4 is definitely a sleeper and by slapping on bigger turbos, plus a few other high-performance upgrades, you'll definitely catch some people off guard. However, adding additional power also means the creation of more heat in the engine. This is when you need to get a high-performance all-aluminum radiator for your Audi B5 S4. CSF was the first to offer a reliable, drop-in fit option with an acceptable price point offered in the market.
Design & Engineering
All CSF's high-performance all-aluminum radiators include CSF's exclusive B-Tube technology that increases the heat transfer approximately 15% over regular oval welded tubes. In addition, the super-efficient multi-louvered fins maximize airflow through the radiator core for the best radiator core technology and performance in the market. Combined with CSF's industry-leading triple-pass design, CSF's new Audi B5 S4 radiator is sure to check off all the boxes for the high performance and race crowd who need an upgrade in the cooling department. The radiator also features a smooth satin finish for a clean OEM+ look.
CSF's triple-pass technology allows the coolant to flow through the radiator core 3x rather than just flowing across the surface of the core once. This allows much colder ambient air to exchange heat with the coolant for a 3x longer period of time generating the lowest outlet temperature possible. Still with a drop-in fit!
After studying what was currently available on the market for the Audi B5 S4 platform - CSF spent quite a bit of time perfecting the design after the initial prototype. CSF made sure to include machined OEM-style "Quick-Connect" inlet/outlet fittings, as well as machined installation seating areas on the top of each tank that holds the rubber bushing pads for correct and study fitment with no vibrations and no modifications necessary to install. Just another extra step that CSF has taken to continue to make the best cooling products in the world.
Perfectly positioned machined seating brackets for easy installation. The OEM style machined quick-connect fittings are also shown here.
⚠ Fitment Notes
Please note this radiator only replaces the OE 8D0-121-251-AP for Manual Transmission B5 S4 models. Some Manual Transmission models use the OE 8D0-121-251-BD which has a built in Transmission Oil Cooler. If your B5 S4 MT has a transmission oil cooler this radiator will not work as a drop-in fit replacement. You would need to run an external transmission oil cooler or delete your manual transmission oil cooler for it to work correctly.
Audi 8D0-121-251-AP (CSF #7071 Replaces this radiator)
Audi 8D0-121-251-BD
Features
- 2-Row 42mm Core (Dual Core) Featuring CSF's Exclusive B-Tube Technology
- Core Features an Ultra-Efficient Fin with 6.5mm Fin Height and Multi-Louvered Design for Maximum Surface Area Contact
- CNC Machined "Quick-Connect" Inlet/Outlet Connections
- CNC Machined Brackets and Fittings for Superb Fit and Durability
- All-Aluminum Race Style Drain Plug
- Smooth Satin Finish
- "Drop-in Fit" Requiring No Modifications to Install - Accepts All Attaching OEM Components Including "Quick Connect" Hoses, AC Condenser, Mounting Brackets and Fan Shroud
Applications
| Year Range | Make | Chassis Code | Model | Trim | Engine / Trans / Etc | Notes |
| 2000-2002 | Audi | B5 | S4 | - | Turbocharged 2.7L V6 (Manual) | See Fitment Notes |
OEM Part Numbers
- Audi: 8D0 121 251 AP
- Audi: 8D0-121-251-AP
- Audi: 8D0121251AP
- Audi: 8D0 121 251 AP VAG
- Audi: 8D0-121-251-AP-VAG
- Audi: 8D0121251APVAG
