My Jeep has water only in radiator (it IS arizona) but i will be taking it up into the mountains and it gets below freeezin up there. So when i drain the water how much new 50/50 will i need to put in?

If you buy premixed coolant, you need to fill it full of premix (the name 50/50 comes from the fact that its premixed 50% water, 50% coolant) if you buy concentrated coolant, i like to go 60% coolant 40% water here in colorado. i wouldnt go much more either way though.

Your cooling system holds 10.5 quarts of coolant, that type of information can be found in the forum's FAQ at the top of TJ Tech forum's main page.

But even in Arizona, never run just plain water in your cooling system. Coolant contains a lubricant the water pump requires as well as antirust/anticorrosive additives that keep your cooling system from rusting/corroding out. And never run regular tap water either, use distilled. Tap water is loaded with dissolved mineral content, especially there in Arizona, which will clog up your radiator with hard water deposits.

After choosing the percentage mix that you want you can buy a pretty inexpensive tool that will tell you to what cold temperature your radiator is prep'ed to handle. Any of these should do:Amazon.com: antifreeze testers: Automotive

Indeed. Oxidization is your enemy .

Jerry, what is your opinion of "softened" water and "reverse osmosis" water ?

you want distilled (less minerals to cause corrosion)

Reverse osomosis water is pretty good. I'd use it.

'Softened' water still has the 'bonus extras' in it, plus salt! Bad stuff to put in your engine or your battery either.

I only got 2 Gallons in my Radiator before it started to overflow. let the JEEP run for 15 minutes and took the Cap off again and still full. Jerry, you estimated 10.5 quarts but it barely took 8....

also I tried putting the heat on while it was running and it went ftom warm to cool air blowing.

Especially this winter in Colorado...

Like Jerry said, not a good idea to run just water. Also while you have it all drained I would flush the system. This coming summer when it is warm again that's what I will be doing because I don't think it has ever been done.

x2...-2*F this morning, with -36*F windchill

do your cooling system and battery right if you're coming to the moutains. if you don't, you'll only make that mistake once.

-9, warmed up to 2. Now -5...

^I living in VT and I'm planning to impliment a dual battery system , I like the idea of a backup (plus I like to run a power drill off the inverter due to a lack of out side power).

For the coolant I not use anything other than distilled water it is as close to pure H2O as you can get and then add then mix in the recommended dilution of coolant, maybe a hair over.

Not once has my red top failed me. Except for coming home from school, on these cold days, it is having a hard time starting. I think it because the battery is 8 years old and has been drained many times.

It has been so cold in the mornings my windshield wiper fluid freezes to my windshield.