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Cheap brake fluid tester working properly? #4108630 05/28/16 03:00 AM
Joined: Jun 2011
Posts: 77
LucasDK Offline OP
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Joined: Jun 2011
Posts: 77

I bought this tester on Ebay from China:

As you can see from the reviews, people are extremely satisfied with the tester.

I made a test in a bucket of water and it rapidly showed +4% water as it should. But then I tested some old brake fluid which has been on the shelf for 4 years. 4 years ago the container was opened and the plastic screw lid (with no seal) was put on again. It has been resting like this in a shed experiencing summers and cold winters and relative moistures going above 95%.

But my tester shows less than 1% water in the fluid. Which means the fluid should be OK. But can I trust the tester?

PS: I also tried the tester with the brake fluid in my cars brake fluid reservoir and again it showed less than 1%. But I do not know when it was changed the last time because I bought the car 6 months ago (used car).


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Re: Cheap brake fluid tester working properly? [Re: LucasDK] #4108656 05/28/16 04:31 AM
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Ducked Offline
Joined: Oct 2012
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In principle, should be easy enough to test.

Buy some fresh brake fluid (which might be date-coded?).

Test a sample, then spike it with steadily increasing known percentages of water to produce a calibration curve.

That's likely to be more specifically informative than anything anyone on here can tell you about your brake fluid tester.

Re: Cheap brake fluid tester working properly? [Re: LucasDK] #4108657 05/28/16 04:31 AM
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Jetronic Offline
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why not add 1% water to a sample of the brake fluid, and test again?

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Re: Cheap brake fluid tester working properly? [Re: LucasDK] #4108669 05/28/16 04:47 AM
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Posts: 838
larryinnewyork Offline
Joined: Feb 2012
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I have one of those testers.
How reliable is the accuracy ? I don't know.
I tried it a couple times and now it sits in the basement.
I change my brake fluid every 2 years. So no matter what the Tester would show, I should be good.
I thought it was an interesting purchase and may just use mine for reference or to show a family member how bad their (neglected) fluid is.

Read the instructions. It says:
Dip the test probes into the brake fluid up to the plastic rim of the device.

Check for Repeatability by how far you insert the probe.
This is where I was getting inconsistent readings.

Re: Cheap brake fluid tester working properly? [Re: LucasDK] #4108799 05/28/16 08:58 AM
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bowlofturtle Offline
Joined: Jun 2009
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ive only used strips. It was supplied to me by BG products, i think they were rigged a little since it can help BG sell their brake flush. But what do i know.

Honestly now... i dont care too much. I've seen fluid look like used oil in cars from early 90s, the brakes all work and i wouldn't suggest them do a brake flush. My personal cars, i bleed a little every brake job and i'm not thinking twice.

Maybe your test of 100% water was too much water for the tester, LOL

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Re: Cheap brake fluid tester working properly? [Re: LucasDK] #4108964 05/28/16 01:04 PM
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Nate1979 Offline
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The dirtiest fluid is always at the calipers. How are these testers measuring anything useful?

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