CSF High-Performance Auxiliary Radiators for Fxx BMW 340i, 430i, 440i, M140i, M2, and M240i [8355]

CSF High-Performance Auxiliary Radiators for Fxx BMW 340i, 430i, 440i, M140i, M2, and M240i [8355]

CSF has earned an industry-leading reputation in BMW cooling, becoming the top choice for the B58 platform. As Gen-1 B58 vehicles continue to surge in popularity within the tuning community, demand for robust thermal solutions has grown accordingly. In response, CSF introduces High-Performance Auxiliary Radiators for the F87 M2 (N55), F3x 340i / 440i, and F2x M240i / M140i. Designed as complementary upgrades to CSF’s established F87 (N55) and F3x / F2x Cooling Suites, these auxiliary radiators address the limitations of factory systems that emerge under increased power and sustained aggressive driving. For owners pushing the capabilities of their M2s and first-generation B58 cars, CSF delivers the added cooling headroom required to keep performance consistent and temperatures in check.

Design & Engineering

• CSF engineers the auxiliary radiators as a true drop-in fit for both left and right sides. Each unit mounts in the factory location with OEM quick connections and works in concert with the rest of the cooling system to lower temperatures, maintain optimal operating ranges, and extend resistance to heat soak — reducing the likelihood of track sessions cut short for cooldown laps.

OEM vs CSF

• Compared to the OEM coolers, the CSF units represent a substantial upgrade. TIG-welded aluminum tanks are significantly larger than the OE plastic tanks for superior strength and increased fluid volume. A larger 2-row, 42 mm high-efficiency core employs CSF’s exclusive B-Tube technology and the latest 5 mm fin design to maximize airflow, heat rejection, and recovery while preserving flow. With many motorsport programs and enthusiasts pushing 700+ horsepower, the B58 is seeing coolant temperatures rise beyond safe limits—conditions that can trigger limp mode. CSF provides the thermal headroom to keep the B58 performing at its peak.

Construction

• A 100% all-aluminum build ensures performance and durability. The integrated mounting frame is markedly stronger than the OE plastic pod system, while a black finish adds protection and corrosion resistance. For added security, CSF integrates bolt-on rock guards to shield the cores from debris — mitigating the punctures and fluid loss that have plagued OEM coolers and enhancing confidence on road or track.

Features

• Multi-fit – fits both left & right side
• 2-row – 42mm high-performance core featuring CSF’s exclusive B-tube technology
• New 5mm tall ultra efficient fins with a multi-louvered design for maximum surface area contact
• Tank volume and core size increased
• 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

Specifications

• Core Thickness:
  • CSF: 42mm
  • OEM: 27.5mm
• Core Rows:
  • CSF: 2
  • OEM: 1
• Fin Height:
  • CSF: 5mm
  • OEM: 5mm
• Tank Material:
  • CSF: All-aluminum
  • OEM: Plastic
• Construction:
  • CSF: 100% TIG-welded
  • OEM: Crimp-on gasket

Applications

• BMW 340i: F30, F31, F34 (2015-2019) [3.0L I6 Turbo B58]
• BMW 430i: F32, F33, F36 (2016-2019) [2.0L I4 Turbo B48]
• BMW 440i: F32, F33, F36 (2016-2019) [3.0L I6 Turbo B58]
• BMW M140i: F20, F21 (2016-2019) [3.0L I6 Turbo B58]
• BMW M2: F87 (2016-2018) [3.0L I6 Turbo N55]
• BMW M240i: F22, F23 (2016-2021) [3.0L I6 Turbo B58]

Notes

• Certain F3x 340i / 440i and F2x M240i / M140i models were not equipped with dual auxiliary radiators from the factory. Confirm the number of coolers on your BMW with a VIN lookup before ordering.
• There were three auxiliary radiators used on 340i / 440i and M240i / M140i models. CSF #8355 is a direct drop-in replacement for BMW #17-11-8-625-447. It can also replace #17-11-7-628-057 and #17-11-7-600-697 when the appropriate mounting bracket(s) are used. Vehicles not originally equipped with #17-11-8-625-447 may require minor trimming of the air ducting for proper fitment. Models with the M Sport Package and M Sport Brakes typically use #17-11-8-625-447; verify via VIN with your dealership.
• The upper brackets are identical across all three auxiliary radiator variants. Separate frames (cradles) aren’t needed, as CSF #8355 integrates the frame (BMW #17-21-8-625-445) into the cooler design.
• Not compatible with the F87 M2 Competition, which uses S55 auxiliary radiators. On the F87 M2 with the N55, a single CSF #8355 auxiliary radiator mounts on the left-hand side. The right-hand side uses the CSF #8104 Race-Spec engine oil cooler.

About CSF

The Racing & High Performance Division of CSF Inc. is dedicated to designing and producing the world’s most advanced, efficient, and dependable cooling solutions. CSF offers a broad range of state-of-the-art cooling systems, with over 250 distinct applications. These include high-performance all-aluminum direct-fit radiators, intercoolers, and oil coolers, as well as bespoke manufacturing tailored for racecars, power sports, off-road vehicles, marine, and industrial applications. Every cooling solution from CSF is meticulously crafted to ensure optimal engine temperature management, even in the most rigorous driving scenarios. With a legacy spanning over 50 years and more than 40 million cooling units distributed worldwide, CSF is widely regarded as a luminary in the industry.