Brake fluid testers

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Wookey
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Brake fluid testers

Post by Wookey »

Taking the 'diagnostic' term reasonably broadly here (i.e not just electronics), hope that's OK, I wonder if anyone has experience/recommendations for brake fluid testers?

I see you can now buy electronic testers for 30 quid that will tell you how much water is in your fluid. Are they any good? No doubt some models are much better quality than others: some use a laser, some use resistance. Some give a percentage, others just 'OK/bad' LEDs.

I've had much trouble with brakes over the last decade or so (23 year old Expert van) and have bled through a lot of fluid whilst fettling things. My van does very low mileage (0 this year, but normally <3500 miles) I'd really like to be able to test whether fluid is actually knackered or if I can carry on using it. I suspect I'm throwing away a lot of perfectly good fluid, which is just wasteful.

There are probably other ways to test this, like just heating it up in a pan and seeing what temp it boils at (and I see you can buy expensive professional instruments that do this in-situ for £300 or so). (this idea leads me to wonder if you can boil fluid to drive off the water and rejuvenate it somewhat?).
Wookey
Donor 2019
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Re: Brake fluid testers

Post by Wookey »

Hmm, turns out the pen testers are available down to £4 and they all seem to be the same made-in-china model. Some online testing suggests they are quite accurate, at least when new: https://www.youtube.com/watch?v=SHMpxXGkXzw
For £20 you can get a multimeter style one with a dangler that does DOT3,4 and 5.1, complete with a little light on the probe. I see there are also analogue optical refractometers (for £200), and chemical test strips to check the inhibitors. Or you could just measure the galvanic voltage with a meter: https://www.youtube.com/watch?v=No5Hmk9Q_6A. I feel like this would depend on the probe material and maybe some other variables but it may well be how the simple pen testers work - they just save you knowing the scale from voltage to water percentage.

Oh and I was talking bollocks about the lasers. That's just Halfrauds selling the same £4 tester as everyone else for £30 and _calling_ it a 'Laser Brake fluid tester'. Jesus, what are they like!
Gibbo2286
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Re: Brake fluid testers

Post by Gibbo2286 »

Laser is a tool supplier Wookey Halfords are not suggesting anything dodgy.. :-D

https://pmfmag.co.uk/products/laser-to ... alogue-20/
Wookey
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Re: Brake fluid testers

Post by Wookey »

Fair enough. Merely overpriced then :-)
ozvtr
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Re: Brake fluid testers

Post by ozvtr »

You can calibrate your tester to see if it's working correctly.
Draw out 5mLs of brake fluid from a sealed container using a measured syringe. Test it using your tester. Result should be 0%.
Add one drop of water (preferably distilled water) to the test sample. Test it, result should be about 1% or 'less than 2%'. A drop of water is about 0.05mLs.
Add another drop, result 2% or less than 3% and so on.
I think the pen testers only read 'greater than 4%' as the maximum value and 'less than 2%' being acceptable. So one drop will get you into the yellow and two drops will probably get you into the red.
Of course the more water you add, the lower the % of water (in the solution) per drop, but up to 5% (5 drops) should be accurate enough for testers that give you an actual % reading.
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quintet
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Re: Brake fluid testers

Post by quintet »

I've used the pen testers in the past but found them fairly unreliable, we used to call them the 1% pen as they very rarely failed brake fluid, instead we ended up using refractometers as these cover a number of fluids such as Adblue, coolant, battery acid and of course brake fluid. These always belonged to staff rather than the company so im not sure of the brands, i don't think i can really post a link as it might be looked upon as advertising but if you look up vs0052 it should bring up one particular type/brand (others are available).