Brake Fluid Liquid Tester Pen, DOT 3 DOT 4 DOT 5.1 Brake Diagnostic Testing Pen Tool, Brake Fluid Liquid Oil Analyzer with 5 LED Indicators, Universal Car Accessories

Works as it should Battery was a little tricky to install. It's from the side , not the top. Great value.

People don’t know that brake fluid, over time, attracts and suspends water. It’s corrosive and not good. This device measures amt of water contained in the system by simply dipping it in the reservoir and pushing a button. You’ll need to supply 1 AAA or you’ll get no lights at all. So as the top of the brake fluid reseviours now mostly non- sealed they will zap up moisture. Pressing the brakes pushes pistons to pressurize fluid and expand brake pads or rotor/caliper piston and if there’s water in the reseviour it will be pumped into the brake system to do it’s corroding & oxidation. The entire system should be bled and that is done by applying pressure at the reservoir and opening the brake bleeders at each wheel. That’s best left with professional and his/her equipment… but this tool will left you know if there’s a problem.

Package says battery included. but not. Notice in picture it said battery incl. Makes you think it don’t work. Installed a 2AA battery, works when tested.

Everyone should have one. One older car fluid I checked was good but a newer car failed the test. who knew.

I was shocked that this actually worked perfectly

I accidentlly left my brake bleeder cap loose in the middle of a humid night while I paused to finish the work the next day. Got realy worried about contamination so I ordered this and it showed 0% water content. Was able to complete my brake fluid fluid with peace of mind thanks to this handy little tool :)

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I gave it 4 stars because I have no way to check it's accuracy but with the testing I did it seemed to report the results that I expected. I'd buy it again.