S63TU4 Billet Coolant Reservoir

The RK Autowerks S63TU4 Billet Coolant Reservoir is engineered and machined in-house to provide a robust solution for the known issues with the stock plastic coolant reservoir in BMW M5 and M8 models. This all-metal construction, made from 6061 billet aluminum, guarantees a leak-free experience and a lifetime product, eliminating concerns about future failures. The design thoughtfully retains the OEM factory cap, preserving the intended pressure bleed-off function. All original connecting points are utilized, and the quick-connect fittings simply slide on, making it a straightforward plug-and-play installation. The reservoir also incorporates the stock sensor for accurate coolant level readings and features internal baffling to dampen fluid transfer. This billet reservoir addresses the critical issue where the OEM plastic reservoir is prone to leaking, which can cause significant damage to injectors and coils, leading to vehicle downtime and potential engine damage. Replacing it with another plastic unit offers an uncertain lifespan, making the billet option a more reliable long-term investment. Key features include 6061 billet CNC construction, retention of the OEM factory cap and sensor, utilization of OEM connections, and internal baffling. The product supports a range of BMW models, including the 5' F90 M5 LCI (07/2019 — 06/2023), 5' F90 M5 (01/2016 — 06/2020), 8' F91 M8 Convertible (11/2017 — 02/2025), 8' F92 M8 Coupé (11/2017 — 02/2025), and 8' F93 M8 Gran Coupe (10/2018 — 02/2025). Installation requires reusing the stock coolant sensor probe and OEM gas cap. In some cases, the sensor may not slide out smoothly and might require trimming around it for removal; an O-ring for the sensor is included. Customers are responsible for verifying part number fitment. RK Autowerks is not responsible for units purchased incorrectly due to failure to cross-reference part numbers.