Coolant Loss Due to Leak from Expansion Tank on BMW Z4

Problem Description and Possible Solution

An engine coolant leak may develop from the expansion tank resulting in engine overheating. When a cooling system component fails the entire cooling system should be inspected. It is not uncommon to find additional component have failed or are leaking.

Overheating can cause severe engine damage. If the engine begins to overheat it is recommended to stop at the first available location and have your vehicle towed to a repair shop.

Problem Data
RepairPal Verified
Average mileage: 76,255 (58,000–107,000)
4 model years affected: 2003, 2004, 2005, 2008
20 people reported this problem
Viewing 1 - 11 of 11 comments
Found a hairline crack in the coolant expansion tank that was causing a slow leak. I replaced the tank and the problem was resolved.
bought 1 week ago.after 4 days coolant light came on.tank bubbling and water leaking from it.taken to garage.engine runs nice.
Expansion tank started leaking, expansion tank, upper,lower hoses are being replaced. costs $700 at mechanic, $1500 at BMW service. I go with mechanic
2" hairline crack on the front of the expansion tank resulting in spewing coolant everywhere on the floor