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Brake Fluid Testers #4605311
12/16/17 11:28 AM
12/16/17 11:28 AM
Joined: Aug 2004
Posts: 309
San Diego
FlyPenFly Offline OP
FlyPenFly  Offline OP
Joined: Aug 2004
Posts: 309
San Diego
How accurate and effective are tools like this?

https://www.amazon.com/gp/product/B06Y42GSDW/ref=oh_aui_search_detailpage?ie=UTF8&psc=1

If you're just testing the fluid reservoir, is that accurate enough?

I have 2 vehicles, both with fluid factory 3.5 years old and they pass fine. Curious if that's accurate or what.


2014 Mercedes GLK350 3.5L DFI
2014 Mercedes E350 Coupe 3.5L DFI
2007 Suzuki Grand Vitara 2.7L V6
Re: Brake Fluid Testers [Re: FlyPenFly] #4605316
12/16/17 11:39 AM
12/16/17 11:39 AM
Joined: Sep 2015
Posts: 3,939
Connecticut
69GTX Offline
69GTX  Offline
Joined: Sep 2015
Posts: 3,939
Connecticut
I had my car's 13 year old brake fluid tested with strips at a Quick Lube place...and they told me it was still "good." In any event, I ended up changing it myself a few months later. I don't know how test strips can tell how much water or oxidation is present in the brake fluid.


----------------

2001 Lincoln Cont 4.6L DOHC/ 39K mi / QS HM 5w30 / FUG XG2
1999 Camaro SS M6 /19K /Mobil 1 0w40 /Fram UG /GM MTL-ATF
1969 Ply GTX/RRs
Re: Brake Fluid Testers [Re: FlyPenFly] #4605318
12/16/17 11:42 AM
12/16/17 11:42 AM
Joined: Sep 2012
Posts: 5,461
DFW
DBMaster Offline
DBMaster  Offline
Joined: Sep 2012
Posts: 5,461
DFW
I'm curious about this, too. I have a similar tester that indicates my fluid is still good after 5.5 years and 83,000 miles. The fluid in the MC still looks straw colored. The tester measures moisture content in the fluid through conductivity.

Re: Brake Fluid Testers [Re: FlyPenFly] #4605328
12/16/17 11:55 AM
12/16/17 11:55 AM
Joined: Apr 2015
Posts: 423
Reunion Island
Superflan Offline
Superflan  Offline
Joined: Apr 2015
Posts: 423
Reunion Island
Ok hereís what I think. Since thereís no cycling of fluid in the reservoir, the quality of fluid in the lines, abs actuators and calipers are undetermined.

Yet, on modern cars, pistons calipers are designed to not conduct heat generated when braking to the fluid, therefore claiming that no replacement is necessary during the normal life of the vehicle.

I had results confirming this on some cars, but on a car where I got brake vapor lock the test clearly showed a lowered boiling point of 120 degrees centigrade


Peugeot Partner 1.9 D, 5W40 C3, 245000 Km, running on WVO
Wife's Mitsubishi Outlander PHEV, dealerís overfilled, 16000 Km
Re: Brake Fluid Testers [Re: FlyPenFly] #4605330
12/16/17 11:57 AM
12/16/17 11:57 AM
Joined: Aug 2004
Posts: 309
San Diego
FlyPenFly Offline OP
FlyPenFly  Offline OP
Joined: Aug 2004
Posts: 309
San Diego
I guess there's an underlying assumptions here then: Moisture is the only reason to change brake fluid, is that true?

Flushing the brakes and testing the old fluid that comes out of the calipers also seems to be another data point to verify.


2014 Mercedes GLK350 3.5L DFI
2014 Mercedes E350 Coupe 3.5L DFI
2007 Suzuki Grand Vitara 2.7L V6
Re: Brake Fluid Testers [Re: FlyPenFly] #4605333
12/16/17 12:00 PM
12/16/17 12:00 PM
Joined: Mar 2012
Posts: 1,367
San Antonio, TX
E150GT Offline
E150GT  Offline
Joined: Mar 2012
Posts: 1,367
San Antonio, TX
I have one of those cheap pens. I tested new brake fluid and it tested good. I took a small sample and added some water and it tested bad. I tested the reservoir in a 2003 tundra and it showed good. It looked terrible though.


1984 Mercedes-Benz 300SD - 100k
1995 F150 XL 4.9 reg cab 5MT - 251k 5w30
2016 Mazda6 Touring 6MT - 57k 10w30
2006 Buick Lucerne CXL 3.8 31k 5w30
Re: Brake Fluid Testers [Re: FlyPenFly] #4605342
12/16/17 12:24 PM
12/16/17 12:24 PM
Joined: Nov 2013
Posts: 1,156
UT
BHopkins Offline
BHopkins  Offline
Joined: Nov 2013
Posts: 1,156
UT
I've also had the same question about the similar brake fluid tester that I own.

My plan is to mix up a test solution - 20 ml of fresh brake fluid with 1 ml of water for a 5% moisture solution, and see what results I get with the tester. Perhaps this might be something I can to this afternoon.


2013 Subaru Outback 2.5i - Idemitsu 0W-20 & Mobil 1 filter
2007 Mercedes SL550 - M1M 5W-40 & MB OEM filter
Re: Brake Fluid Testers [Re: FlyPenFly] #4605362
12/16/17 12:50 PM
12/16/17 12:50 PM
Joined: Feb 2014
Posts: 2,449
[email protected] CZ firearm factory
Marco620 Offline
Marco620  Offline
Joined: Feb 2014
Posts: 2,449
[email protected] CZ firearm factory
Dont have a tester but the Honda light will come on telling me brake fluid exchange is necessary.


15' Civic R18 200,090k 0w20 Redline/Archoil9200/TEIN/Eibach/Injen/Tanabe Sustec/Borla Exhaust!
Going for 238,900 milestone. My house to moon is 238,900 miles!
Son of a Navy Corpsman. Support veterans!


Re: Brake Fluid Testers [Re: FlyPenFly] #4605416
12/16/17 01:36 PM
12/16/17 01:36 PM
Joined: Dec 2014
Posts: 1,684
'murica
Ethan1 Offline
Ethan1  Offline
Joined: Dec 2014
Posts: 1,684
'murica
I'm surprised to hear the mixed reviews of the testers, because I never had reason to doubt the concept of testing resistance as a way to extrapolate H2O content. confused

Re: Brake Fluid Testers [Re: FlyPenFly] #4605422
12/16/17 01:49 PM
12/16/17 01:49 PM
Joined: May 2016
Posts: 718
Canada
i_hate_autofraud Offline
i_hate_autofraud  Offline
Joined: May 2016
Posts: 718
Canada


It's more then H2O content, it's also oxidation and seal material wearing and clouding the brake fluid,
eventually this material precipitates and sticks to cylinder bores and cuts into seals when pistons are
pushed back to allow new pads to fit. Seen it!

Replace on a 2 or 3 year cycle is a safe bet compared to replacing an ABS unit when it malfunctions and stores
a pesky code! At that point you have 'regular' brakes!

For that reason, I don't use a brake fluid tester.

Re: Brake Fluid Testers [Re: FlyPenFly] #4605428
12/16/17 01:59 PM
12/16/17 01:59 PM
Joined: Sep 2005
Posts: 5,909
MIchigan
Warstud Offline
Warstud  Offline
Joined: Sep 2005
Posts: 5,909
MIchigan
The test strips test for copper because : as your brake lines corrode.... more copper ends up in the fluid.

The test pens test for water.

Re: Brake Fluid Testers [Re: FlyPenFly] #4605665
12/16/17 05:50 PM
12/16/17 05:50 PM
Joined: Jan 2017
Posts: 484
Virginia
Hemispheres Offline
Hemispheres  Offline
Joined: Jan 2017
Posts: 484
Virginia
Itís a good idea to change it a every few years due to crud more than moisture. Remove 1/3 of the fluid from resivior, fill back up and remove another 1/3 then vacuum bleed. Keeps the pistons and lines in good shape internally.


2009 Buick LaCrosse (3800 Series III) - 137,000 miles.
PZ Plat HM/Mobil 1 HM
Bosch/Purolator/Mobil filters
Re: Brake Fluid Testers [Re: FlyPenFly] #4606308
12/17/17 02:27 PM
12/17/17 02:27 PM
Joined: Jan 2016
Posts: 334
Cheshire, England
barryh Offline
barryh  Offline
Joined: Jan 2016
Posts: 334
Cheshire, England
As far as water content is concerned I would say a reservoir test is representative. The hydroscopic nature of brake fluid will ensure any moisture diffuses throughout the whole system. As already mentioned there are other reasons to change brake fluid. I would want a test to show when the corrosion inhibitors had been used up but I suspect a reservoir test for that might not be representative of the whole system.


Barry

1979 BMW R45 (Triple QX 5W40)
2009 Mercedes C180K (Shell Helix Ultra 5W40)

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