ECS Tuning MINI R5X Heavy Duty Aluminum Coolant Expansion Tank (17137823626)

Gen2 MINI R5X models (R55, R56, R57, R58, R59, R60, and R61 chassis) utilize a closed, pressurized cooling system to maintain optimal engine operating temperature. At the center of this system is the plastic expansion tank, which is constantly exposed to piping hot, chemical-laden antifreeze. After years of use, the expansion tank degrades. This degradation causes the tank to turn brittle and yellow, eventually leading to micro-fractures, cracking along the factory blow-molded seam, or worse, a catastrophic break. Because coolant loss under pressure can occur rapidly, a failing stock tank frequently leads to severe overheating issues or unexpected roadside breakdowns.

Our Heavy Duty Aluminum Coolant Expansion Tank directly addresses every structural flaw of the factory unit (17137823626) by replacing molded plastic composition with a fully TIG-welded 5052 aluminum construction. Aluminum eliminates the risk of seam separation, cracking, or heat deformation, providing a permanent solution that handles pressure and heat without expanding or fatiguing. To ensure exact fitment, the tank was designed using 3D CAD modeling, allowing for plug-and-play installation in the factory location. Unlike many aftermarket alternatives, no cutting, drilling, or custom brackets are required for installing the ECS Heavy Duty Aluminum Expansion Tank!

All hose barbs, bleed screws, and sensor ports are CNC-machined to precise tolerances, guaranteeing a leak-free seal with factory quick-disconnect hoses. A precision-designed threaded cap fitting ensures buttery smooth integration of the factory cap, as well as a precision seal with internal cap O-rings. To aid in serviceability, an integrated internal fill-level sightglass eliminates guesswork, allowing you to easily view your coolant level at a glance. The heavy-duty wrinkle black powder coat isn't just for aesthetics—it protects the exterior of the tank from corrosion and engine bay heat, maintaining a clean, OEM+ look for years to come.

** Cap Design yellow warning on it now like OEM **

FEATURES

• Manufactured from 5052 and 6061 aluminum and fully TIG-welded, providing high structural strength that easily withstands elevated engine temperatures and extreme cooling system demands
• Pressure tested to 31 psi, ensuring absolutely zero fluid leakage, and consistent system pressure far exceeding normal operating conditions
• Features a clear external sight glass set at the low-level mark for rapid, at-a-glance coolant checks, alongside an internal bent sheet metal fill tab to identify the exact full capacity level during service
• Designed to use all factory mounting geometry—sliding directly into the lower rubber mount and snapping over the stock retaining tabs
• Hose inlet, outlet, and cap connections are CNC-machined to exacting tolerances
• Wrinkle black powder finish protects raw aluminum from oxidation while providing a clean, OEM+ look
• Replaces OEM plastic expansion tank part numbers 17137539267 and 17137823626 across all Gen 2 MINI R56-R61 platforms

KIT CONTENTS

• Heavy Duty Aluminum Coolant Expansion Tank
• Coolant Expansion Tank Cap

PRODUCT DEVELOPMENT

Our Heavy Duty Aluminum Expansion Tank was designed, engineered, tested, and quality inspected by our Research & Development team. Our development process includes leading-edge product technology: FARO laser scanning for reverse engineering and quality inspection, SolidWorks 3D CAD modeling, rapid prototyping utilizing our in-house 3D printer, and rigorous long-term product testing.

INSTALLATION

To aid in the installation process, we've assembled a start-to-finish installation guide, including detailed instructions on removing your factory cooling expansion tank and associated components. Click the "INSTALLATION" button above for complete instructions.