To clear "Cavitation" as suspect:
There is a pH indicator ( Bromothymol Blue ) that turns blue in a slightly alkali state. Blowing CO2 through it will make it acidic ( carbonic acid ... Aka "carbonated water", same stuff that makes soda pop fizzy ).
Temporarily replace your radiator cap with a stopper and some aquarium "airline tubing" or similar, so that any exhaust gas will be routed via the tubing into a bubbler ( soda pop bottle filled with the indicator solution ). It turns a yellow ***-color when CO2 is bubbled through. You can test it by just blowing through the bubbler yourself. You have enough CO2 in your breath to detect. To reset the indicator back to blue, drop in a little extremely diluted lye ( sodium hydroxide-NaOH-Drain Cleaner Lye ) - dissolve a pinch of lye powder in a little bottle of water, drop some in, and shake. You want it right at the edge so it's most sensitive to even a little CO2. The chemists call this a "titration". I think you can buy the blue indicator fluid already prepared for detection of exhaust gas in the coolant at Harbor Freight.
If you buy Bromothymol Blue as a small vial of powder, you will have enough to make gallons of indicator solution. If interested, ask "duck.ai"
( Below is Chat GPT-5 )
Bromothymol Blue pH indicator
GPT-5 mini
Bromothymol blue — quick reference
Chemical type: Sulfonphthalein pH indicator
Formula: C27H28Br2O5S
Appearance: Greenish-blue crystalline powder (solution is blue to yellow depending on pH)
pKa (approx.): 7.1
Color change range: pH 6.0 (yellow) → pH 7.6 (blue); green near neutral (~7.0)
Common solvent: Ethanol or water (often prepared as 0.04% w/v in ethanol then diluted)
Typical lab prep (indicator solution): Dissolve 0.04 g bromothymol blue in 100 mL ethanol, then dilute to 1 L with distilled water (gives ~0.04% stock); final working concentration usually a few drops per 10–100 mL sample.
Uses: Titrations around neutral pH, monitoring CO2 in water (carbonation/respiration), classroom acid–base demonstrations, biological assays (pH ~6–8).
Safety: Harmful if swallowed; avoid inhalation and skin/eye contact. Refer to MSDS for handling, storage, and disposal.
Storage: Store in a cool, dark place in a tightly closed container; protect from light.
If you want: exact preparation volumes for a specific final concentration, an MSDS link, or a procedure for using it in a titration or CO2 test, tell me which and I’ll provide it.
Test
