I beg to differ -- freezing point depression and boiling point elevation are very closesly related, and a 50:50 mix of ethylene glycol and water will not boil (at sea level) until around 230F. With the pressure in the cooling system, it won't boil until about 240F, I believe. Boiling point of pure water is 212F. Pressurizing the cooling system will only raise the boiling point to 220 F. This isn't adequate, as the water will boil inside the head where the surface is considerably hotter than the coolant in bulk ever gets, insulating the head from the coolant and causing severe overheating.

I strongly recommend using 50:50 antifreeze mix in the tropics for protection against boilover -- the minimal reduction in heat transfer ability should be compensated for by the use of a tropical radiator (larger than "normal" for temperate zones), not by using plain water. If the tropical radiator doesn't do the trick and there isn't anything wrong with the engine (ie good head gasket, engine KNOWN to be free of scale, etc), an oil cooler is an excellent idea. This will remove considerable heat from the oil, resulting in both less engine heat AND better lubrication. Most older MB's had oil coolers (all the diesel do anyway), but if one isn't present or the factory one is too small, an aftermarket on is a good idea.

Plain water without an anticorrosion package equivalent to the anticorrosion chemicals in the antifreeze will result in serious corrosion of the aluminum parts of the engine, too.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!