One problem related to tank assembly has been reported for the 2000 BMW 540. The most recently reported issues are listed below.
While driving on the freeway ran over a piece tire. Consumer heard tire strike vehicle. Consumer proceeded to drive. Next day upon entering garage there was a very strong smell like gas, and gas was all over the ground. Consumer could see tank was moist after looking undernieth. Took to dealer, and they will replace fuel tank. Consumer felt a piece of tire should not puncture a fuel tank.