Mine split just below the upper hose connection nipple on the plastic end cap at a spot close to where Bluebee pointed to in the diagram. It happened on the way home after picking it up from the dealer. Luckily I was near an exit on interstate 95 and was able to get it off at the exit and shut down. It had 76K on it when I took delivery. One thing compounded the problem, the pixels on the cluster were so bad that I couldn't read the warning of low coolant. When the high temp alarm came in I could just barely make out the "TEMP" part and only then knew exactly what was happening. Luckily I was within 500 ft. of the upcoming exit and could get off and shut down quickly before any serious damage happened. The dealer towed and replaced the radiator as MA has a mandatory 3 mos/3.6k warranty for all used vehicles under 90k total miles. BTW, I've since had the cluster replaced under the BMWUSA goodwill program.