I stumbled upon this device in a YouTube video a week or two ago. I was replacing pads and rotors on all four corners of my son’s RAV4, and I was presuming I would flush the brake fluid too. But then I saw this device demonstrated and decided to buy it.

It’s operation is very simple. You dip the metal probes into the brake fluid in the brake fluid reservoir and press the button. The LEDs indicate the percentage of H2O in the brake fluid. It turned out that the brake fluid in the RAV4 tested okay.

It’s been 3+ years since I replaced the brake fluid in Redrover, so doing that again was on my list. But I tested the brake fluid in Redrover and found it too was okay.

Flushing the brake fluid is not difficult, but it does take some time. Having this tool will save me some time and effort and bring some peace of mind too.
I think it's worth the $5.99.

 

what was your reading ? I hear if you get above 4% time to change the brake fluid

 

It was <1%.

 

That looks very useful. Any consensus on whether or not testing it at a caliper is relevant? I would assume not, since there's probably more likelihood of moisture appearing at the cap area for sealing reasons, but does water "settle"? I’ve seen plenty of rusty pistons and bores in systems that otherwise looked "ok" (I guess) at the reservoir.

 

Might be worthwhile to keep a small container of "known bad" B fluid on hand so we could test the tester.

 

Thats a good point John. I remember many years ago being sceptical about an antifreeze tester. We tested it on pure water and it said it was good to -15C or thereabouts.

 

Fair point, but what is "known bad" brake fluid?

If one were motivated enough one could sacrifice/invest in a pint of new brake fluid and carefully add water in calibrated amounts to check the calibration of the meter.

I'm not that motivated.

The guy in the video admitted this isn't a highly precise, lab grad meter, but claimed it was at least reasonably accurate for most users.