CUTLASS Best way to flush/change coolant?

86LK

Royal Smart Person
Jul 23, 2018
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Following is just a swag... Scientific or (Silly) Wild A** Guess. Don't know your exact specs so pulled from Rock Auto 34 x 18.125 x 1.25 Core. For tanks just extrapolated it as 3 columns = (1.25 thick x 18.125 high x 1.5 wide).

Core is 770.3125 cubic inch or 12,623.1603 CC

Tanks (SWAG) ... 67.97 cubic inch or 1,113.829 CC

Total = 13,736.9893 CC/ml = 13.74 Liters = 3.63 Gallons.

And you are probably around 60% of that = approx. 2.2 Gallons?

Still seems kind of high.

About the only way to do it, unless you can find out actual capacity from GM books, would be to:

Remove and lay radiator flat make sure it's empty and add measured amounts of water and total that up.

Figuring the wife doesn't want her good Pyrex out in the garage, I would suggest the 1 or 2 quart plastic paint container and pour into radiator until full. Keep track of total quarts poured and total up and convert to gallons. 4 quarts = one gallon.
yeah, 2 gals seems high until you realize the whole system holds about 16-18 qts, including the engine block. so the engine block holds 2 gals also?
I looked at all the radiators listed on Rock and not a single one listed fluid capacity.

even the Spectra website gave no capacity

even these numbers are all over the place
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78Delta88

Royal Smart Person
Supporting Member
May 23, 2022
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SW Arizona
Same here, I'm sure it's in a GM book somewhere.

Basically the best way is just fill it and measure/log how much was put it. Or fill it and measure what came out.

Doing the process engineering for manufacturing, I rather like to know what I do have instead of what I should have.
 
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Rt Jam

G-Body Guru
Mar 30, 2020
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Ontario Canada
because I want to.

it lets me plan on what I should be expecting

If you are aiming for a 50/50 mix after a radiator swap. You can just add premix. This assumes there is a proper mix on what is left in the engine and heater system.

There is documentation on entire cooling systems or as 78Delta said, measure it yourself.

Another idea is to sample the mix and check the freezing point with a coolant tester. Don't overthink it. Close to 50% is plenty adequate.
 

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