Cooling System Question

Nice comprehensive answer bwrench. You get a GA from me.

The only thing I'd want to add is that there really isn't such a thing as a closed system. Before I produce a flurry of comments following this reply, let me explain. I know that any sudden, significant drop in coolant will be caused by a leak somewhere. You superbly covered these sources and how to detect them in your reply, but some losses cannot be avoided. Most vehicles today have an overflow tank with coolant. While the vapor pressure of the antifreeze will be very low, the water will still be able to evaporate to the air. Also regardless of the tightness of any seal, particularly a moving seal like at the water pump, some capillary wicking will happen. For all of these unavoidable paths to make a noticeable loss of coolant, months of daily use will have to happen.

OK! I agree with you on not using straight water, but if 50% is good, is 100% better?

From the Peak website:

A. Why is it important to mix antifreeze with water?
Antifreeze contains chemicals that protect your engine against rust and corrosion, as well as freeze-up and boil over protection. Water is required to activate the chemicals in the inhibitor package. Furthermore, adding water to antifreeze actually increases the freeze-up and boil over protection provided. For example, a mix of 40% antifreeze and 60% water provides freeze-up protection down to -10°F and boil over protection up to 259°F. In comparison, a mix of 70% antifreeze and 30% water provides freeze-up protection down to -62°F and boil over protection up to 270°F. However, we do not recommend adding more than 70% antifreeze. This would limit the corrosion and freeze up protection and heat transfer capabilities of the antifreeze.

"First, why does it call for a 50/50 mix of antifreeze and water?"

Because the manufacturer formulates antifreeze to have the maximum "antifreeze capability" with a 50/50 water mix. As I recall a 50/50 mix of antifreeze/water will protect down to -34 degrees F.

All the anti-boiling propaganda started in the 60's as a way to get consumers to use antifreeze year round.

I don't know where the 50/50 business came from, but it is not the word of God. Water is a better coolant than antifreeze. You only need enough antifreeze for the coldest temperature your car will experience. I live in Texas and my car is garaged, so it never even gets down to 32F. So I use no antifreeze. My coolant is distilled water plus a bottle of Red Line Water Wetter, which has all the good chemicals found in antifreeze. I've been doing this for 15 years with no problems.