What's the coolant capacity on 98 2.5L w/ac?

[atikovi]

The owners manual says 7.2 quarts. I flushed out the system and changed the hoses so there was little water left in the block. I got a whole gallon of 100% antifreeze back in plus maybe one or two quarts of additional water. (I did use some of the antifreeze in the over flow bottle.) After driving it around so everything gets mixed, my coolant tester shows the mix is only good down to -15F when a 50/50 mix should be at -34F. So obviously it holds more than 7.2 quarts. So how much of this mix do I drain out and replace with 100% antifreeze to get it closer to -34F?

 

[cbr600rx7]

Where do you live? -15F is good unless you live some where that falls below zero on a normal year. If you are trying to raise the freezing point I would drain maybe 1Q and add the same amount of 100%.

 

[atikovi]

Where do you live? -15F is good unless you live some where that falls below zero on a normal year. If you are trying to raise the freezing point I would drain maybe 1Q and add the same amount of 100%.

Well, the antifreeze has corrosion inhibitors to keep the iron block from dissolving so I want to keep it at least 50/50. And -15F is plenty low for my area but if I sell the truck it could go to a colder place.

 

[tomw]

You would have to live a long time for the iron block to dissolve. There are still engines made over 100 years ago that are intact. Back then water was the coolant, with either draining overnight, or possibly some alcohol added to the water to inhibit freezing.
To know how much to add, you would have to know the capacity of the system, and the current percentage of antifreeze/water. No other way. Even if you impute the capacity, you are working from not knowing how much the gallon added lowered the freeze point. What was the previous low? If you did not know that, you do not know how much 1 gallon lowered the freeze point, so you don't know how much to add to lower it further.
You could get closer by draining the system completely into a container, adding some 100% to that mix, measuring protection, and then adding more as needed. Sneak up on it, and then throw the mix back into the cooling system. But, again, the remainder in the block and heater core will muddle the results, giving an imperfect 50:50 mix. Impossible, no, but not worth it, IMO.
The alternative is to drain some out, and add some 100%. Let it run for a while & test.
I do not see how to know how much to add, as you don't know the volume now. If you just guess based on the table on the anti-freeze container, you should come close.

tom

 

[cbr600rx7]

I am well aware of how antifreeze works. Depending on your location some people will run up to 70% water mix for improved cooling and they have no issues. In fact some performance guys select to run 100% water with a small amount of rust prevention additive and have no issues.

Having AC or no AC also has no effect on your cooling systems capacity.