Brake Fluid Liquid Tester Pen, Hydraulic Fluid Liquid Oil Moisture Analyzer with 5 LED Indicators, Auto Brake Fluid Content Detector for DOT 3 DOT 4 DOT 5.1, Car Accessories

After testing I guess I am guilty of letting the brake fluid age too long. Brake fluid is “hydroscopic” it attracts moisture in spite of operating in a system that is supposed to be sealed. This tester indicates it is time to flush and replace the brake fluid. My vehicles specify DOT 3 fluid. I prefer to install DOT 4 fluid as it meets a higher standard specification and is negligible in added cost.Moisture in the system can cause internal rust in the brake calipers, which can cause binding in the caliper pistons. Worse case it can cause the sensitive valves in the antilock brake pump to stick, a replacement that is hard to afford $$$.

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It works pretty good also is a good price.

This Sylvil Brake Fluid Liquid Tester Pen, Hydraulic Fluid, Oil Moisture Analyzer with 5 LED Indicators, Brake Fluid Content Detector that works for DOT 3, DOT 4, DOT 5.1, Car Accessories is an inexpensive way to be sure. With the kids driving older cars, I've been working on older cars more recently and when I get them, I like to know the condition of the fluids. I like that this tester helps me figure out if fluid is safe.

The media could not be loaded. Like most car DIYers, I know (!) that you're supposed to change your brake fluid every few years (the number of years varies by car maker). That's because brake fluid absorbs water over the years, and once that water content gets high enough, this starts to cause problems in your brake system. The major issue would be rust inside your brake system (and you know that can't be good).Until now you could only count on your regular maintenance interval to guide you as to when you need to change the brake fluid (or more accurately, to "flush" it by pumping fresh fluid from the reservoir to each of the four brake calipers).But with this VERY economical device, you KNOW when you need to do this vital service. In my case, living in Arizona, it's logical to assume that you will be able to wait considerably longer to do the fluid flush, because of the very (!) low humidity. If you live in the Pacific Northwest, chances are you might actually get to the point where a flush is prudent before the manufacturer's interval.The unit is calibrated with individual LED lights showing various levels of water content. 0, 1, and 2% would indicate that the service is not yet needed. 3% indicates that it would be a good idea to flush the brake fluid, while a 4% indicated water content indicates a level that could cause problems. Simple!To use the unit, just remove your brake fluid cap (and filter "cup" if so equipped) from your reservoir, remove the cap from the tester, and insert the two (generously long) electrodes into the fluid, and press the button on the top of the unit. The LED(s) will illuminate, and stay illuminated for reading (handy if your brake reservoir isn't too accessible).You do have to supply and install a AAA size battery.All in all, I have to say this is a great deal, a very useful device, and a superb gift for that wrench-twister who's normally so hard to buy for.