Our Aluminum Expansion Tanks for the E46 323i 323Ci 325i 325Ci 328i 328Ci 330i and 330Ci completely solves a common problem with the factory E46 expansion tanks. The stock plastic expansion tank gets brittle over time and eventually fails. When this occurs, you dump a lot of coolant, and that can cause a whole list of problems.
It's not just the original BMW expansion tank that fails, either. Any OEM-style tank is going to suffer from the same shortcomings and failures as the original. Made from plastic, they do nothing to resolve the underlying issues and you are only inviting another inconvenient failure at some unknown point down the line. Beyond the usual mess when coolant is dumped on the ground, the E46 is extra special: when the plastic tank fails, it's usually somewhat spectacular. The released pressure often takes out your hood - an impressively devastating feat.
Before it fails, replace your old plastic unit with this beautifully-made, high-quality aluminum piece from Moroso. The Moroso expansion tank for the E46 non-M is a premium, race-quality reservoir. The expansion tank drops in like an OE reservoir. This tank also includes a two bar reservoir cap.
To learn more about Moroso expansion caps and cooling system pressures, check out this video:
Note: Tank does not have a provision for OE level sensor - dash warning light must be turned off by shorting two wires going to the level sensor plug.