Mixing coolant

[Russ]

I've often seen the following advice on this board in regards to flushing the cooling system: drain and refill the radiator with distilled water until it runs clear, and then fill up the radiator with straight antifreeze to achieve a 50/50 mix; fill up the overflow tank with a 50/50 mix (did I get that right, or have I misread/misunderstood something?) Here's an argument against the final refill portion of this method that's been presented to me a little while ago: since the contact surface area inside the engine/radiator for the 2 fluids is so small, the fluids will not mix effectively. Furthermore, any and all antifreeze/water mixtures should be produced outside of the engine for the same reason. Personally, I don't see how it would be possible for the two fluids NOT to mix inside the cooling system. After all, if that was the case, then the first part of this procedure would not work, since the water would not mix with the old coolant. What do you think?

 

[moribundman]

quote:

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drain and refill the radiator with distilled water until it runs clear, and then fill up the radiator with straight antifreeze to achieve a 50/50 mix;

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If you fill the empty radiator with straight (full strenght) antifreeze, how do you get a 1:1 mix? I premix coolant and distilled water in the proper ratio and simply add that to the cooling system.

 

[Russ]

In my experience, the radiator will usually hold roughly half the cooling system capacity. Therefore, if there is straight water in the block and radiator is empty, filling up the radiator with straight antifreeze should give roughly 50-50 mix (or am I way off here?) Whenever I do a single drain and fill, I always add the premixed solution to the radiator. I tried to do this type of flush (multiple drain and fills) a few years back, but lost track of how much water was in the system, got lazy, and just added 50-50 mix to the radiator. On the first below-25 F-day the following winter the radiator cracked and had chunks of nice green ice hanging all over the cracks (if I remember correctly, it was fine with 32F and a little below, but when it got down to mid 20s, this wonderful even occurred).