Measuring Coolant Concentration

[Burkeomatic]

What is the best way to check the coolant concentration with our coolant? Do the little cheapie prestone ones from the parts stores work? Or do you need a refractometer? If the little floaty ball ones work, my car needs some coolant drained, and some water added. Because it reads 100% coolant on the little cheapie prestone checker.

[Valpo A7]

Those little testers should be accurate enough to tell you how much coolant and water you have in the system. That being said its possible you have a bad tester and if you have access to a second tester or are willing to buy a new 1 then recheck it.

This only tells you the coolant/water concentration and not how healthy the coolant actually is.

[Burkeomatic]

Those little testers should be accurate enough to tell you how much coolant and water you have in the system. That being said its possible you have a bad tester and if you have access to a second tester or are willing to buy a new 1 then recheck it.

This only tells you the coolant/water concentration and not how healthy the coolant actually is.

Thanks, I'll buy another one, they are only like 5 bucks. I usually know 100% what percentage it is, because I am very particular when I fill my cars. However, I didn't perform this coolant fill, and I have some reason to doubt the individual that did. I'll go water heavy when I refill when I upgrade my HX anyways. Just one of those little frustrating things when someone else works on your car. The coolant should be healthy. It was replaced in April.

[gk1]

Using an antifreeze refractometer is the preferred method.
It is also the Audi service manual method. (Official Tool T10007A)
I'm sure there are more expensive Audi or snap-on branded ones I'm sure, but there are plenty on Amazon...like this.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Burkeomatic]

Thanks, I was going to buy a refractometer, but I picked up another 3.99 cheapie from walmart, since I got pissed and threw my other one away. Well, I took a big old glug out of my overflow, and pegged it with max concentration. So I emptied that into some gladware, and dropped another big glug of coolant in there for good measure. Then I came inside, and dropped a glug of water in there, and viola! It is reading lower concentration. I am not sure what the concentration is through my not so scientific experiment, but I would say it is greater than 60-70%. 2 parts coolant from the car to about 1 part water dropped it down to about 30%, if -37C is 50% and 0 C is 0%, I would assume -18 is around 25%.



So I was right not to trust the person that filled my coolant. It makes me wonder what else they screwed up when they changed my timing chain I haven't found yet. It is worth noting when I put my pulley on to go stage 2, and dumped some of the coolant out, I replaced it with only water, so what is in the engine is probably a higher concentration, depending on how much you think they intermingle. Either way, I think I found what part of my IAT problems are, and why I am struggling to get it to cool off. When I put my HX in I'll just replace it with water, so hopefully that will get me to 25%, which is just fine here in south texas. I don't think it has ever been below zero here.

At least I know these work. Not sure how accurate they are for our coolant but they work. It is probably close.

[gk1]

FWIW the prestone antifreeze tester is for ethylene glycol coolants like old G12.
Modern Audi's 2008+ use G12++ or G13 which is propylene glycol so I don't know how accurate it would be.

FWIW I went through this same exercise. I suspect when they opened my coolant system it was refilled with 100% coolant so mixed with whatever 50% mix was still in the system left me at over 80% coolant mix.
As near as I can tell there is a 5º-10º difference between ethylene and propylene glycol on the refractometer. So not huge difference anyway.
So -25C on ethylene is -20C on propylene.... and -40 e /-35 p

Audi states to keep a minimum -25C freeze protection which is 40% coolant 60% water.
50/50 mix offers protection down to -36C

I suppose if you live where it never goes below freezing it is your call, but usually there is little to no benefit to run closer to freezing point and big risk IF you ever do hit freezing temps. IIRC even racers who dump the whole system and refill with straight water and a little "water wetter" don't even see gains from that, just maybe less slippery if it spills. But who knows maybe the 3.0T is different.

[Burkeomatic]

FWIW the prestone antifreeze tester is for ethylene glycol coolants like old G12.
Modern Audi's 2008+ use G12++ or G13 which is propylene glycol so I don't know how accurate it would be.

FWIW I went through this same exercise. I suspect when they opened my coolant system it was refilled with 100% coolant so mixed with whatever 50% mix was still in the system left me at over 80% coolant mix.
As near as I can tell there is a 5º-10º difference between ethylene and propylene glycol on the refractometer. So not huge difference anyway.
So -25C on ethylene is -20C on propylene.... and -40 e /-35 p

Audi states to keep a minimum -25C freeze protection which is 40% coolant 60% water.
50/50 mix offers protection down to -36C

I suppose if you live where it never goes below freezing it is your call, but usually there is little to no benefit to run closer to freezing point and big risk IF you ever do hit freezing temps. IIRC even racers who dump the whole system and refill with straight water and a little "water wetter" don't even see gains from that, just maybe less slippery if it spills. But who knows maybe the 3.0T is different.

Well, the coolest it has ever been here is 0 degrees in 1949. So I would be safe. I am referring specifically to the supercharger cooling loop though. From what I understand, the supercharger and main cooling loop stay relatively separated. At least that is what all those people who think divorcing your system is a waste of time say lol.

[qcrazy]

From someone who has done extensive intercooling system testing, I can confirm they are independent loops. The reservior is shared as a common expansion point for both systems, which is actually a good set-up.

The one and only reason to divorce the two systems is leak control.

On a common system, if an intercooler connection lets loose both the intercooler and the engine coolant will leak out. And with larger intercooler pumps that means you can drain the coolant that much faster. My car currently runs about 11 gpm, meaning I could theoretically drain all the coolant out in a matter of seconds.

On a divorced system, leaks are independent. A leak on the intercooler system has zero effect on the engine's system, and vice versa. While a leak on the intercooler will make the IC system useless, at least the engine would be unaffected and one could continue to drive to get to a safer location.

[Alabama]

Using an antifreeze refractometer is the preferred method.

Is this something you would suggest an owner do routinely, or only if there is suspicion of a problem (like going to the wrong service shop)?

[gk1]

Is this something you would suggest an owner do routinely, or only if there is suspicion of a problem (like going to the wrong service shop)?

Only if you suspect a problem. If you never opened your coolant loop from new there is no real reason to check it. If you lost some coolant and refilled with straight coolant or straight distilled water then it might be worth a look, but even a few ounces top up isn't going to change things that dramatically. FWIW I think Audi even moved away from selling straight coolant and only sell the 50/50 mix.