Eric,

I've been running with straight water also. The problems  I have found is
corrosion in the steel pipes (long pipes to front, x-over pipes etc.) with
attendant rusty gunk in the coolant. Also, the boiling-point is noticeably
lower, low enough to be a problem when driving in mountains or towing.

Erik V.
Massachusetts
84 vanagon
87 vanagon
too many rabbits... (anybody interested in an early eighties diesel rabbit?
I've got several.)