Original BMW Expansion Tank for Intercooler Low-Temperature Circuit, B46/B48/B58 Engines, BMW 2, 3, and 4 Series (2016–2021)

Built for the low-temperature circuit that cools the intercooler, this Original BMW expansion tank holds the coolant reserve for that circuit on B46, B48, and B58 engines in the 2 Series, 3 Series, and 4 Series. Modern turbocharged BMWs split their cooling into two circuits: a high-temperature circuit for the engine and a low-temperature circuit for auxiliary components such as the intercooler. Coolant in the intercooler circuit expands as it heats under load and contracts after shutdown, and this tank absorbs that change in volume through every heat cycle. BMW gives its weight as 313 g (0.7 lb), and production of this number began in July 2015. It is made in Italy and sold as a single tank.

Original BMW Parts carry a 24-month parts warranty.

Because these engines run two separate cooling circuits, make sure you are replacing the intercooler tank and not the main engine coolant reservoir. This part belongs to the low-temperature side. Plastic tanks of this type most often leak at a seam or molded junction after thousands of heat cycles, and age makes the plastic brittle and easier to crack. Clear plastic can also fog over time, which makes the coolant level harder to read. If you trace a slow coolant leak back to the tank, replace it promptly. A leak lowers system pressure, which lowers the coolant's boiling point.

Technical Details

• Manufacturer: BMW (genuine part)
• Part number: 17-13-8-617-045
• BMW part name: expansion tank
• System: intercooler low-temperature coolant circuit
• Weight: 313 g (0.7 lb)
• Production start: July 2015
• Country of manufacture: Italy
• Sold as: one tank
• Warranty: 24 months on Original BMW Parts

Common Questions

Is this the main engine coolant reservoir?
No. It is the expansion tank for the low-temperature circuit that cools the intercooler. The engine has its own separate high-temperature circuit.

What are the signs that this tank is failing?
Look for coolant seeping from a seam, a brittle or cracked shell, or a fogged body that hides the level. A leak can drop system pressure and lead to overheating.

Fitment & Compatibility

Use the table below to verify the year and submodel for your build. PMB Performance has spent over 20 years matching parts to vehicles and can verify this against your VIN.