Testing CO2 Levels in VW Crafter Cooling System: Understanding Color Changes & Head Disassembly

Hello professionals.
The topic is aimed at people who know the subject.
I would like to describe my problem. It consists in the fact that when I test for the content of co2 in the vw crafter, the liquid which is supposed to change its color from blue to yellow during the test, or remain blue, changes it to green. positive, it appears between blue and yellow. I will add that when I make a test test in a functional car, the liquid does not change color, it remains blue. The instruction states that the test is positive if the liquid turns yellow. the liquid turned yellow. I did several dozen of such tests and it was either positive or negative.
And here arises the question - positive or negative test?
How to understand it? Is the concentration of co2 too low to cause discoloration of the fluid, and if so, does it qualify for disassembly of the head?
Please answer only those people who had such a problem, not forgiving.

I was playing with this type of testers based on bromothymol blue, my conclusions are that the testers give a clear result when it is visible from other symptoms.

The symptom is that sometimes it ejects coolant through the tank, so unfortunately this green color does not bode well.

Somewhere I am knocking that green diesels are already bad.

I think so too. When I perform a test test in a working car, the liquid does not change color, which I think means that in my car there is some concentration of CO2 and no air has appeared.

The content of co2 in the air is trace, i.e. about 0.0385%

Isn't it better to connect a pressure gauge to the cooling system and check the pressure if it is too high by accident?
Teses for CO2 content with small purges are highly ineffective.
I stopped believing them a long time ago, and I do them only because the client reminds himself or "wants to check" and then to 100% confirm the diagnosis.
Do not treat this test as an oracle, because you can be very surprised.

andexp wrote:

Isn't it better to connect a pressure gauge to the cooling system and check the pressure if it is too high by accident?
Teses for CO2 content with small purges are highly ineffective.
I stopped believing them a long time ago, and I do them only because the client reminds himself or "wants to check" and then to 100% confirm the diagnosis.
Do not treat this test as an oracle, because you can be very surprised.

But he is the most authoritative. If other conditions are met / hard hoses, cold bottom of the radiator, liquid collapses, no heating / this test is "dead". Is he very ineffective? I doubt it. Branded fluid reacts with CO2. So if he reacts, why should he dye without him? And where does CO2 in the cooling system color the liquid from?
In my cases of using the tester, the fluid in gasoline engines turns green, while in diesels - yellow. I have never investigated why this is so / and I would be happy to know the opinion of a chemist on this subject /, but the tester himself only indicated wrong once / and the total number of tests is maybe 0.01% /. And that was rather my fault, for I had used the aspirator and most likely inhaled the vapors of the liquid which colored the liquid.

Blue + Yellow = Green. The presence of CO2 in the liquid, apparently too little for a complete reaction, or some strange properties of the fluid inhibit it.

Hey, pick up the cutlet ... I have a question, I did a Co2 test and instead of the pressure should go outside this funnel, it's like I'm taking this reaction fluid and the color turns green in gasoline

Hello, I was doing today in several cars for experimental purposes. vectra b 1.8 16v liquid yellow after 2 minutes of the test, bubbles Auto hit the head repair (damaged) Rav 4 2.0 d4d the liquid did not change color, it did not bubble either. Mondeo mk5 1.5 ecoboost the liquid only rose a little, the color did not change after adding gas and releasing the liquid, it rose, it fell and turned green. Was it inhaling dioxide from the air?

Gentlemen, there will always be CO2 dissolved in the liquid - hell they know where it comes from, but I will tell you a curiosity - I drove a car for two years, which had a healthy bubble and stained the indicator in my eyes - there was not much loss of liquid, or other anomalies such as water in oil. So this test is not always reliable. In diesels, the most common indicator of gasket damage, in addition to the disappearance of fluid or excessive pressure in the cooling system, is the greasy black rim of the tank after unscrewing the cap.

I will join the topic. Diesel 1.9 Multijet. From time to time on the outer walls of the expansion tank I see a dried stream of coolant running from under the plug. I remove the traces and after a month or two it's the same again. The liquid does not diminish, it stays on the MIN line. I have not found any greasy stains or slime on the reservoir. Smell and color of fluid normal. I checked the hose going to the radiator. When heated, it becomes noticeably hard, but not so much that it cannot be squeezed at all. I replaced the reservoir cap - with no positive results. I bought a CO2 tester in the cooling system on the auction site. After a 5-minute test on a warm engine, with the turbines up to 3000 rpm. negative result, i.e. the liquid does not change color. The test was carried out twice every six months. During these 5-minute trials, there was a "bubble" in the reaction fluid funnel 2 times. At the earliest opportunity, I will ask the mechanic to test the exhaust gas cooler on the turbine side to exclude that it is passing a small amount of exhaust gas into the cooling system.
One more circumstance - a slightly wavy temperature indicator, especially in winter. I logged the temperature with the diagnostic program since starting the cold engine. The temperature rises properly until it reaches about 78-80 degrees. Then a large circuit opens and you can see the pointer noticeably retract. The reverse of the pointer is also visible when the engine is slightly loaded while driving (while driving).
I called local workshops asking about the possibility of connecting an exhaust gas analyzer to detect the fault. Neither of them has such capabilities. In one of the workshops they did this in the past, but from what I heard, the test was not entirely reliable. What do you think I have a problem with the UPG or a leak in the system?