Ethylene glycol/water and especially Evans have greater ability to transfer heat away from combustion chamber metal than water due in part to their higher boiling points and less tendency to form vapor bubbles. Boiling water does not remove enough heat and requires detuning the spark advance and carb settings to make up for its low boiling point. What you see on your dash gauge is the coolant temperature, but what you really need to worry about is the combustion chamber metal temperature.Īn engine using water as a coolant and under constant load such as climbing a hill will have the coolant in the cylinder head be either in nucleate or crisis boiling states. A coolant with a low boiling point causes cooler temperature gauge readings because it is removing less heat from the engine. Your coolant temperature gauge may show normal or even cooler while your combustion chamber metal is overheating, because steam in the heads is a lousy coolant, and the higher heat around the combustion chamber metal never makes its way to the temperature sending unit or the radiator. When boiling in the cylinder head happens, the water stays cooler since there is less heat rejected into it, but the metal surface temperature of the cylinder head will be higher than it should be. Water does an excellent job of cooling an engine until the load is increased, as in hard acceleration, and the water starts to boil in the cylinder head. That would be true if an engine was only run at idle or low power output such as cruising. Some may believe that water is the best coolant since it has a specific heat of 1. And engine damage is possible from unremoved heat. Engine performance is lost due to water�s low boiling point. This misinformation is specifically addressed thoroughly in the book �Engine Cooling Systems� by Bohacz. Water removes heat from a motor better than anti-freeze (propylene or ethylene glycol)
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