Radium Coolant Tank Kit | 2017+ Honda Civic Type-R FK8 / FL5 & Acura Integra Type-S (20-0827)

The K20C1 runs hard and hot, and the plastic tank managing its coolant has a documented habit of cracking.

Heat cycle after heat cycle, the factory Type-R and Type-S plastic coolant tank grows brittle until it fails, usually at the worst time. The Radium Engineering Coolant Tank Kit replaces it with a 2-piece tank CNC machined from aluminum and anodized for longevity, holding the same internal volume as the OEM tank so nothing about the cooling system's function changes. Aluminum sheds heat better than plastic ever could and shrugs off the coolant pressures race engines build. A direct bolt-in, no permanent modifications.

What You'll Feel

• One less known failure point on track days, where the plastic tank's reputation was earned
• Better heat transfer out of the coolant through conductive aluminum walls
• Fewer air pockets, with the internal swirl feature helping de-aerate the system
• A factory-function install: same volume, same plumbing role, OEM cap reusable
• An engine bay piece that matches the caliber of the rest of the build

Features

• 2-piece billet aluminum tank, CNC machined and anodized
• Internal volume equivalent to the OEM tank, so no coolant capacity is lost
• Two internal chambers with cross-over passages top and bottom, plus an internal swirl feature that aids de-aeration
• Purpose-designed aluminum mounting bracket secures to existing threaded holes; Radium adapter fittings interface with the factory lines
• Reuses the OEM 1.3 Bar Honda pressure cap, or accepts Radium's Type-A radiator caps (sold separately)
• Robust enough for racing coolant pressures; no permanent vehicle modifications

The Details

An expansion tank's job is quiet but constant: give coolant somewhere to grow as it heats, keep the system pressurized to the cap's rating, and let entrained air separate out rather than circulate. The Radium tank does all of it the way the factory intended, just in a material that will not fatigue. The two-chamber internal layout with top and bottom cross-overs plus the swirl feature actively encourages air to leave the coolant stream, which matters on a turbocharged engine that runs sustained load. Installation is bolt-in: the bracket picks up existing threaded holes, the included heater hose (5/16") and overflow hose (7/32") connect through Radium's aluminum adapter fittings to the factory lines, and your existing cap threads on. If you want to raise system pressure for more boiling headroom, this tank pairs with Radium's Type-A caps in 1.1, 1.3, or 1.5 Bar, sold separately.

Kit Includes

• 1x 2-piece billet aluminum coolant tank
• 1x Aluminum mounting bracket
• Aluminum adapter fittings
• 5/16" heater hose and 7/32" overflow hose
• Stainless steel hardware

Applications

• 2017-2021 Honda Civic Type-R FK8
• 2023+ Honda Civic Type-R FL5
• 2024+ Acura Integra Type-S