Cooling concentration and pressure considerations
I tested my cooling system for pressure handling with a bicycle pump, and tested the concentration of antifreeze with a float hydrometer.
It turns out the cap is opening at 10psi, and I'm at 30% antifreeze. Both are way below spec. My Zerex g-05 ethylene glycol based coolant is rated to boil at 128C with 15psi of head pressure at a 50/50 ratio.
To raise the concentration, I'm going to replace coolant with pure antifreeze according to this formula:
(0.3(3-a)+a)/3=0.5
where a = antifreeze volume replacing current fluid
0.3 = current concentration
3 gal = system volume
0.5 = desired concentration
This suggests I need to replace 0.86 gallons of coolant with pure antifreeze to get up to a 50% mixture. To raise the opening pressure, I ordered a new 16psi radiator cap.
I will also be cleaning out the radiator with degreaser, as my radiator is still clogged with oil from the oil cooler blowing. I'll also be adding a VERY VERY large external oil cooler using aircraft grade hardware.
I still need to open up some basic chemistry textbooks to estimate my final boiling point. I'll be using a 16 psi radiator cap, but on the mountain pass at 4,160 ft I'll be at 12.7 psi ambient pressure (2.1psi below sea level pressure) so I need to consider this factor as well. I'm guessing the boiling point will be somewhere around 125C, allowing me to safely run up to 120C.
Edit: Boiling point estimate
Based on
this PDF, a good rule of thumb is that 1 psi of pressure raises the boiling point by 3 degrees F. Therefore, based on my coolant specs I expect my boiling point will be about 127C at 4,160 ft with a 16psi cap and a 50/50 mixture. Therefore, I can safely run up to 122C, and will set an audible alarm at 120C for the climb.
Driving Plan
I'll try to hit the pass at the coldest possible time, which should also have the least traffic. This means hitting the summit right before sunrise, which means between 5am and 6am where it should be under 70F even on the hottest august days.