I honestly do not think it would harm the engine. Now for under pressure, is the coolant pump not belt driven? That would be what circulates the fluid. The representative made a comment that you could open the cap while the engine was hot. I doubt they would engineer a fluid that is harmful to an engine. Most modern day cooling systems that run water/glycol are pressurized any ways are they not? Pressure is just a by product of the water mix in the system, is pressure really necessary, especially if there is a better fluid that does not create it? Good question for Evans. I am sure a quick call to their Corporate/R&D in Sharon, CT might have the answer!
