BMW Coolant Expansion Tanks

This radiator expansion tank is used on E39 528i 525i 530i from 1999-2003. It is a common failure item. We have found that the expansion tanks should be replaced based on age as well as condition. Expansion tanks seem to have a lifespan of less than six years before they show signs of fatigue and wear. Pre-emptively replacing the expansion tank as part of an overall maintenance plan can prevent you from getting stranded from a sudden failure later on. OEM Hella/Behr brand.

Hella is a premium manufacturer that supplies automotive parts to numerous car brands across the world. Everything from electrical to mechanical genuine parts have been made and supplied directly to BMW before the vehicles ever leave the production floor. Their high quality, long lasting parts have made them a trusted brand chosen to help keep your BMW on the road for many years to come.

As a leading source of high performance BMW parts and accessories since 1993, we at Turner Motorsport are honored to be the go-to supplier for tens of thousands of enthusiasts the world over. With over two decades of parts, service, and racing experience under our belt, we provide only quality performance and replacement parts.  All of our performance parts are those we would (and do!) install and run on our own cars, as well as replacement parts that are Genuine BMW or from OEM manufacturers. We only offer parts we know you can trust to perform!

This item fits the following BMWs:
1999-2003 E39 BMW 525i 528i 530i

This expansion tank cap, from the E30 325is, is designed to give way at 20 PSI instead of 30 PSI, like the stock cap. In the event the system over-pressurizes, this cap should let go first, potentially saving your radiator, hoses, or other vital cooling system components. While there's no guarantee it will save your radiator, this small part could mean the difference between calling a tow service and making it home, and a little extra insurance never hurt. This cap is a high-quality aftermarket part from an OE supplier.

Fits the Following BMWs:

E36 318i 323i 325i 328i M3

Gen 2 MINI R5X models (R55, R56, R57, R58, R59, R60, and R61 chassis) utilize a closed, highly pressurized cooling system to maintain optimal engine operating temperatures. At the center of this system is the factory plastic expansion tank, which is constantly exposed to high heat cycles, vibration, and chemical-laden antifreeze. Over time, heat and pressure leach the plasticizers from the original material. This degradation causes the tank to turn brittle and yellow, eventually leading to micro-fractures, splitting along the factory blow-molded center seam, or catastrophic connection failure. Because coolant loss under pressure can occur rapidly, a failing stock tank frequently leads to severe overheating issues or unexpected roadside breakdowns.

This ECS Heavy Duty Aluminum Coolant Expansion Tank directly addresses the structural vulnerabilities of the factory unit by replacing molded plastic with a fully TIG-welded 5052 and 6061 aluminum construction. Aluminum eliminates the risk of seam separation, cracking, or heat deformation, providing a permanent solution that withstands continuous pressure and heat without expanding or fatiguing. To ensure precise fitment, the tank was engineered using 3D CAD modeling for a direct, plug-and-play installation in the factory location. No cutting, drilling, or custom bracketry is required to secure the unit.

All hose barbs, bleed points, and sensor ports are CNC-machined to precise tolerances, guaranteeing a leak-free seal with factory quick-disconnect hoses. A precision-threaded cap neck ensures smooth engagement with the expansion tank cap while maintaining an airtight seal against the internal cap O-rings. To simplify routine maintenance, an integrated external sight glass and internal level tab eliminate guesswork, allowing you to check your coolant level at a glance. Finally, the heavy-duty wrinkle black powder coat protects the exterior of the tank from oxidation and engine bay heat while providing a clean, OEM+ appearance.