The 2004 BMW 5 Series is mixture of aluminum and steel. The front end from the firewall forward is aluminum with the passenger compartment and rear section constructed from steel. BMW has developed and offers a training program on the only recommended procedures for the replacement of the aluminum front end structural parts. There are 3 rules for repair of the 2004 & later 5 Series BMW and they must be followed to the letter. 1. There is no pulling on the front structure. 2. There is no heat including welding on the front structure. 3. Rules 1 & 2 must be followed to the letter.