Koyo FN2320 Billet Aluminum Filler Neck for 2013-2021 Scion FR-S/Toyota 86/BRZ

Vehicle Fitment

• 2013-2016 Scion FR-S (ZN6, FA20 2.0L H4)
• 2013-2020 Subaru BRZ (ZC6, FA20 2.0L H4)
• 2017-2021 Toyota 86 (ZN6, FA20 2.0L H4)

Fitment Notes

• Does not fit 2022+ Subaru BRZ (ZD8) or 2022+ Toyota GR86 (ZN8) - those are a separate Gen 2 platform and require a different part.
• The OEM stock radiator cap will not fit this filler neck. A deep plunger-style cap is required - Koyorad #SK-C13 or equivalent (sold separately).
• Compatible with OEM radiator hoses and clamps - no hose replacement required at installation.

Features

• Full billet aluminum construction eliminates the steam erosion, thermal cracking, and brittleness common in the OEM plastic filler neck.
• Integrated 1/8" PT female sensor port allows direct installation of a coolant temperature sensor compatible with most Japanese aftermarket temperature gauge brands.
• Converts the radiator cap interface to the more durable deep plunger-style cap (Koyorad #SK-C13 or equivalent), providing a superior pressure seal versus the OEM shallow-style cap.
• Direct bolt-in fit - replaces the OEM plastic filler neck with no modification, drilling, or cutting required.
• Compatible with all OEM radiator hoses and factory clamps, eliminating the need for additional cooling system components at install.
• Manufactured by Koyorad in their ISO 9001-certified, privately owned facilities - the same quality standard applied to their full racing radiator lineup.
• Sensor port is supplied with an optional threaded plug for use when no temperature sensor is installed, keeping the system sealed.
• Designed for both daily street use and track driving, offering long-term durability under repeated high-temperature heat cycling.

Specifications

• Part Number: FN2320
• Material: Billet aluminum
• Sensor Port: 1/8" PT female fitting (threaded plug included)
• Radiator Cap Interface: Deep plunger-style (OEM cap will not fit)
• Compatible Radiator Cap: Koyorad SK-C13 or equivalent (sold separately)
• Hose Compatibility: OEM radiator hoses and clamps retained
• Platform: Toyota ZN6 / Subaru ZC6 (Gen 1 FA20 chassis)
• Engine: FA20 2.0L Horizontally-Opposed 4-Cylinder (Boxer)

Included Components

• 1x Koyorad FN2320 Billet Aluminum Coolant Filler Neck
• 1x Optional 1/8" PT Threaded Sensor Plug

Product Description

The Koyorad FN2320 is a direct-replacement billet aluminum coolant filler neck engineered specifically for Gen 1 ZN6/ZC6 platform vehicles - the 2013-2016 Scion FR-S, 2013-2020 Subaru BRZ, and 2017-2021 Toyota 86 - all equipped with the FA20 2.0L boxer four-cylinder engine. The OEM plastic filler neck on these vehicles is a well-documented weak point, prone to steam erosion, thermal cracking, and cap seal degradation over time, particularly on cars driven enthusiastically or tracked. The FN2320 replaces this failure-prone component with a precision-machined billet aluminum unit that holds up to repeated heat cycling without warping, cracking, or degrading - offering a lasting fix rather than a repeated OEM replacement cycle.

One of the most practical upgrades built into the FN2320 is the integrated 1/8" PT female sensor port, supplied with a threaded plug. This allows owners to install a coolant temperature sensor compatible with most Japanese aftermarket gauge systems - a common mod on these platforms - without requiring additional fittings or fabrication. The cap interface is also upgraded from the OEM shallow-style to a more robust deep plunger-type, requiring the Koyorad SK-C13 radiator cap or an equivalent deep plunger cap (sold separately). The OEM stock cap will not seat correctly on this neck, so a compatible cap must be sourced before installation.

Installation is straightforward - the FN2320 is a drop-in replacement that accepts the OEM radiator hoses and factory clamps with no modification required. It is compatible with both the factory radiator and any Koyorad aftermarket radiator for this platform. This part covers only the Gen 1 ZN6/ZC6 chassis; it does not fit the 2022+ Gen 2 Subaru BRZ (ZD8) or 2022+ Toyota GR86 (ZN8), which share a different cooling architecture and require a separate filler neck. For owners looking to eliminate a known cooling system weak point, add temperature monitoring capability, or simply clean up the engine bay on their FR-S, BRZ, or 86, the FN2320 is a low-cost, high-quality upgrade from one of the most respected names in the radiator industry.