2002 BMW 325

I like to replace all the cooling system components when a failure like this occurs because when the expansion tank fails, the rest of the cooling system is at risk for the same failure. Remove the radiator complete and inspect the thermostat as well. The procedure is not difficult and to make it easier for both of us, get a Robert Bentley repair manual from Amazon. Com so the reference material is at hand for you. There are some special tools required, a fan clutch tool and a pressure tester to be sure you don't have any other leakage.