Brake Fluid Moisture Tester for DOT 3, DOT 4 and DOT 5.1, Color Display With Percent Reading and Alarm, 2 AAA Batteries Not Included
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If you don't love it, return it within 31 days. No questions, no stocking fees.
Brake Fluid Goes Bad Quietly. This Tells You In Five Seconds Whether Yours Has.
Brake fluid pulls moisture out of the air through the hoses and the reservoir cap. A few percent of water drops its boiling point by a hundred degrees or more, and boiled fluid is a soft pedal when you need a hard one. This tester dips into the reservoir, estimates the water content, and shows a percentage, a color bar and an alarm so you know whether to flush now or at the next service. Runs on two AAA batteries, which are not included.
What A Moisture Tester Can And Cannot Tell You
This is a conductivity tester. Water makes glycol brake fluid conduct electricity better, and the probe turns that into an estimated water percentage. It is a fast screening tool, not a laboratory. A shop that wants a number it can defend uses a boiling point tester or test strips; this one costs a fraction of those and answers the everyday question, which is whether the fluid in this car is due.
Two things to know before you trust a reading. First, you test at the reservoir, which is the freshest fluid in the system; the fluid down at the calipers is always older and wetter, so a bad reservoir reading means flush now, and a good one does not mean the calipers are clean. Second, different brands of fluid have different base chemistry. Dip a sealed bottle of the fluid your car uses first to see what new reads, then compare the car to that. If the fluid in the car reads worse than the bottle, it is picking up water.
How To Test In Five Seconds
- Fit two AAA batteries and switch the tester on.
- Open the brake fluid reservoir with the engine off. Wipe the cap and the neck first so dirt does not fall in.
- Dip the probe into the fluid without touching the sides or the bottom of the reservoir, and hold it still.
- Read the display. The percentage is the estimated water content, the color bar puts it in plain terms, and the alarm sounds when the fluid is due.
- Wipe the probe clean with a dry cloth before the next car. Brake fluid attacks paint, so keep it off the fenders.
Why Bother Testing
What water does to brakes
- ✅ Lower boiling point. A few percent of water can cut the boiling point of DOT 4 by a large margin. Hard braking down a long grade or towing can then boil the fluid, and a boiled line gives you a pedal that sinks.
- ✅ Corrosion from the inside. Wet fluid attacks ABS valves, calipers and steel lines, which are expensive parts to replace for the price of a flush.
- ✅ No warning light. Nothing on the dash tells you the fluid is wet. Either you test it or you follow the calendar.
When to use it
- ✅ Before buying a used car. Wet fluid is a tell that the rest of the maintenance was skipped too.
- ✅ Every oil change, so the flush gets done when it is needed rather than when someone remembers.
- ✅ On a shop counter, to show the customer the reading instead of asking them to take your word for it.
- ✅ After a flush, to confirm the new fluid reads like new fluid.
From An Owner
"Worked well. Inserted into my brake reservoir and got the reading. Like the fact it has both a percent reading and colored bars to let you know how old the fluid is and if it needs to be changed."
Specifications
| Tool | Electronic brake fluid moisture tester, conductivity type |
| Fluids | DOT 3, DOT 4 and DOT 5.1 glycol based fluids. Not for DOT 5 silicone fluid or mineral oil systems |
| Readout | Color display with estimated water percentage and a colored bar scale; audible alarm when the fluid is due |
| Probe | Fixed metal probe, reaches the fluid in a standard reservoir, wipe clean between tests |
| Power | 2 AAA batteries, not included |
| Use | One handed, engine off, at the reservoir |
| Weight | About 0.8 lb shipped |
| In the box | Tester and instructions; batteries are not included |
| Returns | 31 day returns, US based support from Towson, Maryland |
Frequently Asked Questions
How often should brake fluid be changed?
Most manufacturers that publish an interval say every two to three years regardless of mileage, and many owner's manuals say nothing at all. If your manual gives an interval, follow it. If it does not, test every oil change and flush when the reading says so or every two years, whichever comes first.
What do the colors mean?
Green is fluid that is still dry enough to do its job, yellow means it is picking up water and should be scheduled, red means flush it now. The percentage next to the bar is the estimate the color is based on.
The tester reads yellow even on new fluid from a sealed bottle. Is it broken?
Probably not; it is reading the fluid's chemistry. Conductivity testers are calibrated for typical glycol fluids, and some brands and some DOT 5.1 fluids conduct more than the tester expects even when they are bone dry. Use the sealed bottle as your baseline: if the car reads noticeably worse than the bottle, there is water in it. If you cannot get a sensible baseline, use a boiling point tester or go by the service interval, and tell us; we would rather know.
Can I test at the calipers instead of the reservoir?
You can dip the probe in fluid bled from a caliper into a clean cup, and that fluid is the oldest in the system, so it is the honest number. For a quick check the reservoir is fine, with the caveat that it is the best fluid in the car, not the worst.
Does it work on DOT 5 silicone fluid?
No. DOT 5 silicone fluid does not absorb water the way glycol fluid does and does not conduct the same way, so the reading means nothing. It is for DOT 3, DOT 4 and DOT 5.1.
Are batteries included?
No. It takes two AAA batteries. Put fresh ones in; weak batteries are the first thing to rule out if readings look odd.
What if it does not work for me?
Send it back within 31 days for a refund. Email support@youcanic.com or call 1-888-959-4265 with your order number.
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