I found an interesting thread on Roadfly (http://bimmer.roadfly.org/bmw/forums/e39/6212121-1.html
) where a pre-2001 upper rad hose design is shown next to the post-2001 "improved" design, which was done apparently to prevent a common catastrophic failure at a coolant tee in the older 2-piece hose.
I bought my '99 540 at 103K miles in mint condition this past October, and could find no service records regarding radiator replacement, and it all looked so virginal under the hood I figured I had all original rad/hoses, etc.
Well, thanks to those photos, I recognized the lower photo (from post-'01) as the hose set-up I have.
So I went out just now and checked, and sure enough, the tee has been moved to a hard plastic "adapter" where the rubber hose connects at the engine.
For further proof that I have the updated stuff I looked at the Conti upper hose markings and sure enough it is stamped with "1Q01", which clearly indicates that it was manufactured in early 2001 and so couldn't have been original to my 10/98 car. So the original owner of my car already experienced it's "Big Radiator Blow-Up"!!
Anyone else out there with a 1997-2000 540: this is good stuff to know, especially if you've bought your car recently.
Wow how about THEM apples? So like, how long do I have to go until THIS radiator & hose fail on me? Am I good for awhile now? I guess I'll really try to squeeze that one non-responsive out-of-town dealer for more history and maybe they'll be able to tell me exactly what was replaced and when. I hate not knowing...