The owners manual for my '03 Suburban says the cooling system capacity for a Vortec 5300 V8 with the Z vin # is 15.8 quarts. So I drained & flushed (3 times) the entire system over the weekend finally adding back 8 quarts concentrated Dex-Cool (not 50/50 premix) along with ~ 4-5 quarts water to bring the whole system up to the fill mark on the coolant tank. 8 quarts coolant should be a little over 50% concentration in 15.8 qt. system.

The only problem is that my antifreeze tester showed -19 degrees when finished, not -34 as you'd expect with a 50% concentration. Borrowed the neighbor's tester ... it too read -19 degrees. Had a shop do some other work today and asked them to check coolant strength. You guessed it ... minus 20 degrees.

<OAccording to the antifreeze tables I could find online, a -19 degree reading equates to roughly a 40% coolant concentration. 8 quarts is 40% of 20-quart system.

So my question is, is the owner’s manual wrong? Do I have more than 15.8 quarts in the Sub? My manual also carries cooling system specs for the Vortec 8100 V8, which as a coincidence is 20.7 quarts.


Thanks for the help.

 

these things are never 100% accurate and you never get 100% of the water out

just drain some fluid and add pure antifreeze then retest...

 

are you looking at the table that includes the rear cargo compartment aux. heater and plumbing and air condtioning or the table that has not got air or aux heater what i have seen is about a 2 1/2 quart differance between the one and the other dont know if that helps

 

Problem solved.

It took about 50 miles to do it, but the coolant reading is now better than -34 degrees. I was going to drain some and add back pure coolant tonight to fix the problem, but it checked out okay before I did that. I'm guessing the water/pure antifreeze installed this past weekend simply wasn't mixed together enough throughout the system to give an accurate reading until today.

So I'd say the owners manual capacity figure is correct.