Moroso 63784 Aluminum Intercooler Coolant Expansion Tank Subaru WRX STI Forester

Vehicle Fitment

• 2002-2007 Subaru Impreza WRX (EJ205, FWD/AWD, all trims)
• 2004-2019 Subaru Impreza WRX STI (EJ257, AWD, all trims - without "sound tubes")
• 2004-2008 Subaru Forester XT Turbo (EJ255, AWD, XT / XT Limited / Sports XT)

Fitment Notes

• For Subaru WRX STI (2004-2019): this tank is compatible ONLY with STI models that are NOT equipped with factory "sound tubes" (intake sound enhancement tubes). STI models with factory sound tubes installed will experience a fitment conflict with this tank's mounting position - verify your specific configuration before ordering.
• Hose trimming required: due to the tank being slightly larger than the OEM unit in all directions, some OEM coolant hoses will need to be trimmed by approximately 1 inch to prevent kinking after installation.
• This tank is a direct bolt-in replacement that mounts in the factory location using the OEM mounting posts on the intake manifold - no drilling, welding, or bracket fabrication required.
• Installation hardware not included - uses existing factory mounting hardware.
• Compatible with stock EJ-series EJ205, EJ255, and EJ257 coolant system configurations. Verify compatibility with aftermarket air-oil separators (AOS) or extensive intake modifications before ordering, as some aftermarket cooling accessories may affect clearance.

Features

• 50% more coolant capacity than the OEM factory tank - provides increased coolant volume for improved thermal buffering and reduces the risk of coolant overflow during sustained high-heat operation.
• Fully fabricated aluminum construction replaces the factory plastic/composite unit that is known to crack, warp, and fail at the filler neck after repeated exposure to high-heat cycling.
• Integral billet aluminum hose fittings - more durable and better-looking than threaded screw-in fittings, and eliminate the potential for fitting failure or coolant seepage at the connection points.
• Billet aluminum filler neck provides a premium, race-quality interface for the radiator cap and resists the same heat-related degradation that causes OEM plastic filler necks to crack.
• Includes a Moroso Racing Radiator Cap in the stock pressure range (14-18 psi) - designed for the Moroso dual-lock filler neck for a secure, leak-free seal.
• Optional upgrade: Moroso Racing Radiator Cap No. 63328 (27-29 psi range) can be purchased separately to increase system operating pressure if desired.
• Finish options: tank can be left as-is (bare aluminum/silver), polished, chromed, painted, or powder coated - suitable for show builds or track builds alike.
• Direct bolt-in design installs in the OEM mounting location - no fabrication required.

Specifications

• Part Number: 63784
• UPC: 084663637841
• Product Type: Intercooler Coolant Expansion Tank (Header Tank)
• Material: Fabricated Aluminum
• Finish: Bare Aluminum (polishable / paintable / powder-coat ready)
• Capacity: 50% more than OEM factory tank
• Filler Neck: Billet Aluminum
• Hose Fittings: Integral Billet Aluminum
• Cap Pressure (included): 14-18 psi
• Optional High-Pressure Cap: Moroso No. 63328 (27-29 psi, sold separately)
• Warranty: 90 Days
• Package Dimensions: 7.4" (L) x 7.3" (W) x 6.7" (H)
• Weight: 1.7 lb
• Hardware Included: No (uses factory hardware)
• Made in USA (Guilford, Connecticut)

Included Components

• 1x Moroso 63784 Fabricated Aluminum Coolant Expansion Tank
• 1x Billet Aluminum Filler Neck (integral to tank)
• 1x Moroso Racing Radiator Cap (14-18 psi)

Product Description

The Moroso 63784 is a direct bolt-in aluminum coolant expansion tank (also known as a header tank) engineered to replace the factory plastic unit on the 2002-2007 Subaru WRX, 2004-2019 Subaru STI (without sound tubes), and 2004-2008 Subaru Forester XT Turbo. The EJ-series turbocharged Subaru platform is well-known for running significant heat through the intercooler cooling circuit, and the OEM plastic expansion tank is a documented failure point - cracking at the filler neck base, warping under sustained heat, and leaking coolant after repeated thermal cycling. The Moroso 63784 eliminates this weakness permanently by replacing the plastic tank with a fully fabricated aluminum unit that is inherently resistant to the heat and pressure cycles that destroy factory tanks.

The tank provides 50% more coolant capacity than the OEM unit, increasing the thermal buffer available to the intercooler cooling circuit during extended high-load driving, track use, or aggressive street performance. The integral billet aluminum hose fittings are machined directly into the tank body - a stronger and more leak-resistant design than the threaded screw-in fittings used by some competitors. The billet aluminum filler neck accepts a Moroso Racing Radiator Cap in the stock 14-18 psi operating range, which is included. For owners who want to run increased system pressure, the Moroso No. 63328 cap (27-29 psi) is available separately and threads directly onto the same filler neck.

Installation is a direct bolt-in using the OEM mounting posts on the intake manifold - no drilling, welding, or bracket fabrication is needed. Some OEM coolant hoses will require trimming by approximately 1 inch to prevent kinking, as the Moroso tank is slightly larger than the factory unit in all dimensions. The bare aluminum finish can be left as-is for a clean motorsport appearance, or treated to polishing, chrome plating, paint, or powder coat to match any build aesthetic. One critical fitment note: STI models equipped with factory "sound tubes" are not compatible with this tank due to the mounting clearance conflict - confirm your STI does not have sound tubes before ordering.