CSF CSF BMW F8X M3/M4/M2C Auxiliary Radiators

CSF SKU: csf8258


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( CSF #8258 )

CSF is the #1 cooling choice for BMW and particularly F8X M3/M4/M2 Competition owners. With an industry-leading reputation and overwhelming success as the cooling experts, CSF has added the final piece to the already popular F8X Cooling Suite.


Like the other cooling systems on the F8X, the factory auxiliary radiators do a pretty good job in stock form. However, once you start adding a lot of power and pushing the car in aggressive driving conditions, the factory systems start to show its limitations. As more and more owners have pushed the limits of their S55, CSF saw the need and demand. The F8X platform is also almost a decade old with the newest examples being at least 5 years old. Over time the original coolers end up with damaged or clogged fins that greatly reduce their cooling capacity.


Design & Engineering

CSF designed the coolers to be a true “Drop-in Fit” for easy installation. Each cooler mounts in the factory location and uses the OEM quick connections. The High-Performance Auxiliary Radiators work in conjunction with the rest of the cooling system to reduce temperatures. They not only help keep temperatures in optimal ranges, but prolong the heat soak threshold. There’s nothing worse than having your track session cut short because you need to do a cooldown lap.

Each CSF F8X Auxiliary Radiator can fit the left or right side. The fitting and plugs are swappable and can be easily setup for either side.


Feature OEM CSF
Core Width & Rows 41mm – 1-Row 42mm – 2-Row
# Cooling Tubes 24 27
# Cooling Fin Rows 25 28
Fin Height 8mm 6.5mm
Design All-Aluminum
100% All-Aluminum
TIG-Welded Construction


Compared to the OEM F8X coolers, the CSF units are a significant upgrade. CSF eliminated the OE plastic mounting pod by incorporating it into the modular design that fits both sides. This design improvement increases the size of both the core and tanks. The extra space taken from the mounting pod allowed for a ~7% increase in Core Size and an ~10% increase in Tank Volume. With a larger 2-row 42mm core, cooling efficiency and capacity are drastically increased. The high efficiency core using CSF’s Exclusive B-Tube Technology maximizes airflow and heat dissipation. 100% All-Aluminum construction ensures the best performance and durability. The mounting pins and brackets are much stronger and more durable than the OE plastic pod mounting system. In addition, the black finish provides extra protection and offers a stealthy look behind the grilles of your F8X.

In addition, the CSF auxiliary radiators also feature integrated bolt on rock guards to keep the coolers safe. You’ve no doubt heard horror stories about OEM coolers getting punctured and spilling fluids all over the road or track. Now you can feel more confident that your cooling system is safer from road debris.

Modular Design

CSF used a modular design so the auxiliary radiator can fit either side. There are several benefits to this type of design and offers several benefits. One of those benefits is for serious track applications. Having spare parts is always a great idea. Having one auxiliary radiator that fits both sides where you’d normally need one of each is a big cost and space saver. Getting an extra as backup is more cost/space efficient with the CSF units.

F8X S55 Cooling System

The F8X S55 cooling system is decently complex. Diagrams have been included for anyone who doesn’t understand how the whole system flows.

The cooling system consists of 6 to 7 heat exchangers depending on your transmission. Numbers below refer to the graphic above.

1. Auxiliary Radiator (Right Side) – Charge Air Cooling System
• CSF #8528 – High Performance Auxiliary Radiator
2. Radiator – Engine Cooling System
3. Front Mount Heat Exchanger – Charge Air Cooling System
 CSF #8075/8075V – High-Performance Front Mount Heat Exchanger
4. Charge Air Cooler – Charge Air Cooling System
 CSF #8082 – Dual-Pass Top Mount Charge-Air-Cooler
8. Auxiliary Radiator (Left Side) – Engine Cooling System
• CSF #8528 – High Performance Auxiliary Radiator
9. Oil Cooler
 CSF #8220 – High-Performance Engine Oil Cooler
10. DCT Transmission Cooler
 CSF #8081 – Dual-Pass Race-Spec DCT Transmission Cooler

Because each auxiliary radiator is used for a different system you can elect to replace one at a time. For those looking to further improve the Charge Air Cooling system replace the right side auxiliary radiator. Those looking to improve the engine cooling system should replace the left side.



BMW F8X M3/M4/M2C Auxiliary Radiator Features (CSF #8258)

  • Sold Individually – all applications require 2 auxiliary radiators
  • Multi-Fit – Fits Both Left & Right Side
  • 2-Row 42mm High-Performance Core Featuring CSF’s B-Tube Technology
  • Ultra Efficient 6.5mm Tall Fins with a Multi-Louvered Design for Maximum Surface Area Contact
  • Tank Volume increased by 10% and Core Size Increased by 6.4%
  • 100% All-Aluminum TIG-Welded Construction
  • OEM Style “Quick Connect” Inlet/Outlet
  • True “Drop-in Fit” Requires No Modifications to Install
  • Includes Detachable Rock Guard
  • Individually Leak and Pressure Tested
  • High-Performance Upgrade Suitable for Professional Racing, Street Performance, or OEM Replacement
  • Satin Black Finish for OEM+ Look
  • 2 Year Limited Warranty
  • Applications:
    • 2015-2018 BMW F80 M3 (incl. CS & Competition)
    • 2015-2020 BMW F82/F83 M4 (incl. CS, GTS, & Competition)
    • 2019-2021 BMW F87 M2 Competition (incl. CS)
  • OEM Part Numbers:
    • BMW: 17-11-2-284-603 / 17112284603 (Left)
    • BMW: 17-11-2-284-604 / 17112284604 (Right)