I’m about to flush my cooling system and I want to make sure I get around 8.4 liters out. How do you recomend calculating drained liquid?
In your title you say DRAINED fluid.
In your post you say FLUSH.
Which is it?
Because there’s a difference.
Tester
This is easy. Drain till it is empty, fill till it is full and then go drink coffee.
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I don’t get it.
I’m flushing my cooling system. To do so, I gotta drain the liquid from the system.
It’s just I’m putting back OEM Blue coolant and I think there is green coolant. Mixing coolants is not good. I will be doing 2 cycles of putting back some deionized water to clean and some chem flush but the only way to make sure it’s totally empty is to calculate 8.4 liters of fluid that came out.
How are you flushing the system?
Tester
Removing the drain bolts. On expansion cap, radiator and I belive there is one last under the engine block somewhere.
That’s a drain, not a flush.
Once all the coolant is drained, either add a premix of 50/50 coolant, or fill the cooling system with pure antifreeze that equals 50% of the cooling systems capacity, and finish filling with distilled water.
Tester
Well I’m flushing all the coolant out of it. What is the difference?
I will be doing a 70/30 mix. That’s why I want to make sure there is enough taht come out. I don’t want to start mixing my coolant and not knowing there is still stuff in there.
So back to OT, how do you recommend calculated drained or liquid in a bucket?
Measure the vessel into which you drain it. Multiply the width x length x the height (depth to which the fluid rises. Subtract the radius of the curvature of the bottom edge of the straight length of the four edges combined.(if there is a radius) squared x 3.1416 divided by 4. Also subtract the radius squared x 3.1416 x 3.1416. 
OR, just pour the fluid you drain out into a vessel marked for volume… in short, measure it. 
Refill with the same volume you drained out, operate the vehicle, and recheck the fluid IAW the manufacturer’s procedure in the owner’s manual.
It’s good that you stated “around” 8.4 liters. There’ll be fluid entrapped in hydraulic circuits and in the torque converter that’ll prevent an absolute total drain. The good news is that an absolute total drain isn’t necessary. But repeating the drain process is never a bad idea if you want that “extra margin”. It gets out much of the residual fluid that didn’t come out the first time.
No torque converter it’s a 6 spd manual. Yeah I will do 2 water cycles with 1 chem flush bottle in each.
I just ahd an idea I have empty 2L Coca cola bottles. I’ll just fill them up.
I just did something similar. I drained from the bottom of the radiator (stopcock) into something like an aluminum roasting pan. I had two to rotate if necessary.
I transferred the drained liquid into empty distilled water bottles (gallon size) and used them to measure. And compared to specs in owner’s manual to know how much was left in system.
My drain was slow (even after waiting for reservoir tank to empty and then opening the radiator cap). Turning on the heat with engine on before starting increased the amount of liquid that drained out.
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How do people turn something so simple into rocket science?
And by the way, a 70/30 mix is of no benefit. It can actually cause problems with the cooling system.
Tester
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If you’re referring to my post… I was just having some fun. Measuring is always the best and by far the easiest and most accurate way to determine volume. 
Yeah it’s to no benefit, it’s better for my system to freeze than work amirite? It can get to -40c here, that’s -40f. A 50/50mix protects to -36f. What happens if it does go to -40c this winter. I’m in a bad situation?
And I thought a 70/30 was ok. It’s not like I’m putting 100% coolant.
Unless I’m missing something and a few degrees difference don’t matter much?
Yeah.
I live in Minnesota. And we see those kind of temperatures.
And when it gets down to -40 degrees, nothing usually moves.
You have to look at how many days in a row you’ll see those temperature extremes.
Tester
The back of the bottle will tell you exactly how variations in the ration will affect the coolant’s ability to withstand low temperatures. There’s a chart.
For some odd reason, I was thinking “tranny” rather than “cooling system”. I must have “tranny on the brain” today. Apologies for that.
But I’m worried let’s say mix is rated to -35c and it gets to -45c. Will I be ok if Idon’t drive or will the freezing make the hoses expand and stuff could get damaged that way? That’s more what I’m worried about here.
-40???
Screw the flush and move somewhere warmer! lol!
Why would you use any mix other than the one for the lowest temperature?
Wait… did you say -35C? That’s -31F, within the limits that I recall being on the coolant charts. One thing I recommend is that if at all possible you get a plug-in engine heater overnight. When I lived in a subzero climate I had a lower radiator hose heater and it worked fine. It was like a little 12V tea heater. The heated coolant would migrate via convection through the engine and the warmth would go with it.