The coolant expansion tank in your vehicle gives additional fluid a place to go after expansion and contraction from temperature change. Because it is subjected to such drastic changes on a regular basis, it can often crack or break. If your tank has experienced such damage you will need to replace it.

When replacing, be sure to also have replacement coolant shipped to your door. Most German vehicles require specialized coolant, be sure to pick up the proper coolant when refilling to avoid damage or premature corrosion.