Brake Fluid Testing

[moby4dick]

I’m getting ready to flush my brake fluid, as I purchased a 2018 vehicle last year and have no idea if it was ever flushed. Found you can get a cheap tester, looked up some youtube videos as I wondered how accurate they were. I was really impressed with this video:



Reason being, most videos just had someone doing very unscientific testing. This guy actually measured out precise amounts of brake and water concentrations to test the cheap pen tester and seems surprisingly accurate.

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[Vlad Soare]

Nice one.
I wonder if the brake fluid is really perfectly homogenous. I mean, if there's 1% water at the top of the reservoir, does this mean there's also 1% water at the farther end of the brake pipes, or in the calipers?

 

[moby4dick]

Nice one.
I wonder if the brake fluid is really perfectly homogenous. I mean, if there's 1% water at the top of the reservoir, does this mean there's also 1% water at the farther end of the brake pipes, or in the calipers?

That’s a great question. I picked up one and checked my fluid, it showed 0%. I checked an open bottle of Motul RBF600 (meaning capped, but seal open) from 3 years ago and it showed borderline okay, 2%.

When I get around to bleeding I’ll test what comes out.

 

[bankyf]

We tried using them in my shop and they were all over the place (15-20 cars a day for 6+months). Couldn't get a dependable repeatable readings out of any of that style. They erred towards failing most of the time, so it helped us sell brake flushes, but we ended up going to the Phoenix test strips. I believe that some of the inconsistencies were due to different types of fluid (DOT3,DOT4, LV, etc.). After using the strips for a bit, it became clear that the moisture content also doesn't tell the whole story about the condition of the brake fluid.

 

[TeeLew]

Brake fluid is a little bit like a condom. If you have any questions, change it.

 

[moby4dick]

So prior to my first track day ever last Sunday (what a blast! Hoping I can get another one in sometime soon), I bled the brakes. Tested the pumped out fluid and it was consistent with the reservoir fluid, 1%. So at least for me, I’m pleased with the accuracy.

 

[TeeLew]

Brake fluid is a little bit like a condom. If you have any questions, change it.

Dammit! It just occurred to me that the *REAL* punch line to this joke should have been "If you have any questions, flush it and start over with a sealed replacement."

This is my joke! You guys can't use it.....well, ok, if you read it here you're cool, so, you can use it.

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