You are missing the fact that the petcock is the lowest point in the cooling system and most all the coolant/water will drain when the petcock is opened. 50/50 is a starting point, but to get the correct mixture you need a coolant tester that shows the freezing point and make sure the mixture is under the lowest temps for your area.

 

You are missing the fact that the petcock is the lowest point in the cooling system and most all the coolant/water will drain when the petcock is opened.

Thanks for the response!

It seemed as though only a gallon or so would drain from the petcock, but that could be because (a) I had the radiator cap and/or bleed screw off, breaking the vacuum, or (b) the Jeep is at a nose up incline. Level parking is a scarce commodity around here. I'll turn it around and see what happens.

Regarding the antifreeze/water ratio, assuming you're right about the petcock, the problem is effectively solved and I'll have at it tomorrow morning. If I have doubts I'll pick up a hydrometer and test it.

 

For years now I've simply always used premix. No calculation ever needed, even for topping off. No concerns about mineral or other content in the water.

 

If you are concerned about the volume of water left in the system after you drain your radiator affecting your ability to have a 50/50 mix, then measure the volume you drain and subtract that from the total volume of the system. A simple calculation will tell you what concentration of coolant/distilled water you need to add to end up with a 50/50 mix.

 

the total volume is known number. never ever seen any vehicle really drain much from the pet cock alone. but if say you have flushed it to clear. Now say the total capacity is 2 gallons. with the system full of just water now remove one gallon add one of pure antifreeze. 50/50.

 

Right, and this was how I approached it. But it's not how most write-ups are written up.