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Discussion Starter · #1 ·
Did a flush & fill in my '98 5.7L Suburban. Added straight dex-cool to the radiator, and about the right amount of water to the overflow, figuring they would mix together. Drove around with the heater blasting on high long enough to get it up to normal temp, plus another 10-15 minutes. The overflow is still just water.

How long will I have to drive it until it mixes it so I can use my coolant checker & see if I need to change the mix? (should be near 50-50 as is, but I want to be sure of course)
 

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It will take a while to get it to mix in the overflow tank, because it is an overflow tank (and you don't have to run with the heater on, it circulates through the core at all times and uses a door under the dash to adjust the airflow). When it cools down, open the radiator cap and use your checker in the radiator.
 

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Discussion Starter · #3 ·
Oh well, I guess it's an excuse to go play. :great: As long as everything's good by winter, it's all good...
 

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the over flow only comes into play when real hot --then as it cools. the raditor cap allows any pressure high than the spring allows to push its way into the overflow---then as the motor cools it creates a vaccum and sucks water from the over flow. this will take many times starting and running and sitting to do any type of mixing. you can cheat some if you have a relief cap (lever on top) you can run the motor and let sit a few min and release pressure and repeat a few days and it will mix faster. mike
 
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