Quote:
Originally Posted by Excaliber
Olddog, I suspect it takes very little over pressure from steam or air or whatever to raise the cooling system pressure beyond the cap rating and start pushing water out. Evans Coolant, no pressure!
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I'm not clear on what you meant here, and I'm not trying to put words in your mouth (fingers as the case may be).
We purposely raise the pressure in a radiator system to increase the boiling point of the water/glycol.
Evans Coolant would run at the same pressure as water, if you did not change the cap. They are choosing to run at a lower pressure by modifying the radiator cap, because the boiling point is higher.
A radiator cap is a pressure relief valve. As the coolant expands from the temperature increase the pressure must rise until it pushes against the spring in the cap hard enough to relieve.
You get a better heat transfer in a heat exchanger at higher pressure. I'm not so sure that just because you can run with no pressure that it is a must do or even the best thing to do.