have often at some time in their past been run with straight water for a summer. While it will work for a summer it causes so much rist in the block that it is hard to get them clean enough a few years later to cool properly. And lots of thermostats aren't very accurate or stick part way open.
And then that thing about water pumps disintegrating - once took one apart (off an old international harvester school bus) that had almost no trace of the impeller blades left... just rusted away.... I'm guessing it was run on straight water or very old antifreeze with no rust inhibitors left in it.

__________________
Thanx,
Alberta Luthier
1983 300CD ('Stinky')155k miles, 2.47 diff, EGR removed, AAZ injectors with 265 nozzles from Sean,and vogtland lowering springs.
1984 300SD ('Old Blue')150k Klicks from Japan originally, came with rear head rests, no sunroof and never had an EGR