Combustion Leak Detector (fluid) Question

[dibbons]

After the fluid turns from blue to either green or yellow, does it return to blue after the change? I am testing a '92 Jeep Cherokee and I would have sworn the fluid began to change from blue to green but then it seemed it was blue again. Don't know if I am seeing things or if my observations were correct. Thank you. (photo is before the test commencement)

 

[remytherat]

No, it would stay green.

It’s dissolved bromothymol blue, a pH indicator dye. When an acidic gas from combustion bubbles though the water it turns into an acid, decreasing pH and changing the color. This is permanent unless a base is added.

 

[dibbons]

Expected a yellow change, but only turned green. I did not realized my tester has two chambers (see photo in post #1). I believe I should have filled both with test fluid. I might try again doing it the correct way.

 

[dibbons]

At minute 15 the fluid returned to blue. Weird.

 

[dibbons]

Update: Repeated the test to find both chambers turned green. Time to remove the cylinder head and find out once and for all what is going on here.