Four problems related to radiator have been reported for the 1997 BMW 740. The most recently reported issues are listed below.
There's a major flaw design in the BMW 740i and 740il fgrom years 1995-200. I was just driving and it failed without hesitation. I spoke with a lot of other owners of this model and they had the same peoblem. To some people it happend as they were driving on the highway spilling coolant all over their windshield and losing control of their vehicle.
Upper nipple with hose connector on radiator is made of plastic and breaks off with fragments left in the hose. This really should not be made of plastic as intensely hot water passes through it all the time. This amounts to an expensive repair.
I have had three separate failures of plastic radiator components in my 1997 BMW 740il in the space of 5 months. At first inspection, these appear to me to be thermal fatigue failures indicating some manufacturing defect in the plastic. BMW denies any such issue and refused to replace the failed components under warranty. The first instance was a minor leak that developed from a small pipe that exits the top of the radiator. Before I had that repaired, the neck of the top inlet to the radiator broke off while I was driving. The radiator had to be replaced. A little over a month later, I saw steam emerging from the radiator and noted a 1/4" split in the center of the intergral fluid reservoir where water was spraying out. This component had not been replaced when the radiator was replaced. As this was not in a typical stress area like a corner, seam or bottom, I believe this was caused by fatigue. The fact that all of these failures occurred on plastic components so close together in their life implies a common failure mechanism to me. The dealer commented that "they see a lot of these kinds of failures. " as the vehicle has only 70,000 miles on it, this would seem unusual unless there were some underlying flaw in BMW's design or manufacturing of the cooling system.
While traveling at highway speed of 75 mph radiator upper neck to which water hose connects broke from the weld. Dealer notified.