Brake fluid analysis - is it possible?

[Titanium_Alloy]

Here is one for the experts:

Is it possible to do a brake fluid analysis? I was thinking: since some perform engine/atf/gear/ps oil analysis why not to check a brake fluid for wear and contaminations? If I'm not mistaken most of the high quality brake fluid on the market is borate-ester based. What can we tell about a condition of brake fluid from analysis? What tests should be performed? Is it even possible to request such analysis from a lab like a Blackstone, Amsoil, or Shaffer's? Do we need a special kit for brake fluid or a regular oil analysis kit can be used? How much this analysis will cost?


Regards,

 

[bulabula]

I'm not an expert in brake fluid analysis, but I wouldn't bother to sample it, I'd just change it. I thought moisture was the biggest concern. If moisture is present, then all kinds of things can start to happen in there.

Where would you draw the sample? From the MC? I'm not sure how much the fluid circulates, but I don't think it would be an accurate sample on representing the fluid status at each brake cylinder. I certainly don't think it would be cost and time effective to drain a sample from each wheel for analysis.

I like to change mine every couple of years anyways. If you don't care to bleed them, then spend the $25-30 for a shop to do it for you - that would cover the cost of an analysis and your labor.

[ April 09, 2004, 05:56 AM: Message edited by: bulabula ]

 

[cryptokid]

unless you use dot5, it would be cheaper to buy a quart of brake fluid and just change it out than pull a sample.

 

[Bogatyr]

Titanium_Alloy,
I did see something advertised at one point that was a test strip that you would dip in the MC reservoir to test the fluid condition. Now, I'm not sure if it would test for contaminants or moisture or what. It was marketed to shops in order to sell brake fluid changes.

But, as bulabula mentions, I'd just change it out every two years or so. Take the money you would spend on analysis and buy a pressure bleeder. It's a great tool and makes the job very easy.

Bogatyr

 

[Bror Jace]

Like Bogatyr, I’ve heard of those test strips. They are probably available for sale … maybe search Google using “brake fluid test”? … but as was pointed out, it’s probably better to swap the fluid out every 3 years or so, depending on your climate, etc … Moisture contamination is the big enemy of brake fluid.

Of course the argument against testing also applies to used motor oil testing. It’s almost always cheaper to merely change the oil and forget about any sort of analysis. However, that doesn’t satisfy the “I wonder if …” which most of us have rolling around in our heads.

Anyway, one thing I don’t like about the dip-in-reservoir testers is that the brake fluid with the least amount of life in it is in the caliper, not in the reservoir. To get a meaningful result, I think you’d have to bleed some out of at least one or two wheels and test them separately. It’d be a pain and I’d only do something like this once to test a certain brand/type of fluid in a certain application.

--- Bror Jace

 

[RavenTai]

most of the moving brake parts are seperated by rubber seals,so you should not find any wear metals in the fluid unless there is corosion

water is the main contaminant, as said above you can test at home for water,

brake fluids darkens over time so i go by color, if it is any daker than honey it needs changing (about every year)

 

[VaderSS]

I'll concur with using test strips for brake fluid.

Main problem with sending it in for analysis, is that, over time, brake fluid does not stay the same across all parts of the system, like other, circulated, fluids. The brake fluid in the calipers and wheel cylinders can get far worse off than the fluid in the M/C becuse it is not recirculated, but stays relatively static, just moving back and forth.

[ April 10, 2004, 09:40 AM: Message edited by: VaderSS ]

 

[Titanium_Alloy]

I have to agree with all of you that proper bleeding every 2-3 years is by far superior method to any changes. I don't think that these brake strips really do work. To perform more or less accurate analysis/testing you need a lab equipment. Although brake fluid in reservoir is not the same as in brake calipers I still think that fluid does circulate through the system. I'm not saying that brake fluid as dynamic as engine oil but temperature changes, pressure difference/change, and other factors have some affect on fluid diffusion. I suppose that argument works in favor of the method by changing brake fluid by replacing fluid in the reservoir. Not very efficient - but probably will work after like 20 changes or so

. By that time you wish you'd done a normal bleeding

.

My question, however, was to analyze brake fluid to see how it behaves with time in a certain vehicle and particular brake system. Also I was wondering if it is possible to detect some kind of internal brake system failure which might be coming, like ABS unit or a master cylinder for example. Analysis results might help to approximate brake fluid change interval as well and general condition of a brake system. I'm not sure though if that would be a reasonable thing to do.

I wish a guy from a Blackstone (who posts only on occasion) would give some feedback on my crazy idea and insight whenever their lab would be able to perform an analysis.

Regards,

 

[XS650]

quote:

---

Originally posted by VaderSS:

Main problem with sending it in for analysis, is that, over time, brake fluid does not stay the same across all parts of the system, like other, circulated, fluids. The brake fluid in the calipers and wheel cylinders can get far worse off than the fluid in the M/C

---

I'm in the change it at least every two years camp too, but for those who want to do test strips, they could take a little fluid out at a wheel cylinder for the test strip.

 

[widman]

There is a certain amount of circulation of brake fluid back and forth, giving a somewhat representative sample at the resevoir. The first thing that you would analize is color, and your eyes can do that. If it is dark, it probably has rubber in it or is oxidizing. Just change it. Second would be viscosity and water which are directly related. I recently had three samples of brake fluid analized since the Nissan Dealer thought there was a problem with our brake fluid when ehty started having a rash of brake problems in certain models.
The virgin fluid came back fine. here are the lab results:
Sample 1 2 3

Vis @ 40c, cSt 7.40 8.17 29.0

Vis @ 100c, cSt 1.96 N. D. N. D.

Water, % wt 0.34 3.41 3.00

Odor Normal Burnt Burnt

In the end the dealer found a new mechanic who confused the water and brake fluid resevoirs on that model (they are side by side).
Best bet is to change out fluid every couple of years. The first things that will go in the sistem are the rubber parts - don't forget hoses.

 

[VaderSS]

quote:

---

There is a certain amount of circulation of brake fluid back and forth, giving a somewhat representative sample at the resevoir.

---

Not enough to be of consequence. The fluid that comes out of the calipers is always darker than what is in the resovoir, in my experience.

 

[labman]

So everybody is blithely going ahead and changing brake fluid without a shred of data that it is needed?

 

[XS650]

quote:

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Originally posted by labman:
So everybody is blithely going ahead and changing brake fluid without a shred of data that it is needed?

---

No, some people wait until the cylinders chew up the seals because of corrosion

 

[TooSlick]

I believe brake fluids are glycol ethers ....

You could probably use reagent strips, ie Litmus paper, to evaluate the change in PH and a hot iron skillet - outside

- to do a crude "crackle" test to quantify the water content.

Or, you could just change the stuff ...;

 

[labman]

quote:

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Originally posted by XS650:

quote:

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Originally posted by labman:
So everybody is blithely going ahead and changing brake fluid without a shred of data that it is needed?

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No, some people wait until the cylinders chew up the seals because of corrosion

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Changing the fluid has no effect out between the O-rings and the boots where the problem is.

 

[ruking77]

I am going to guess that while most of us use color as an indicator, it probably is as unreliable as just looking at the color of the engine oil, as an indicator. A full liter/quart 33.8/32 oz bottle of DOT 4 synthetic cost all of 5 dollars. So for sure, it may not be economical to test like engine oil analysis for example.

 

[XS650]

quote:

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Originally posted by labman:

quote:

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Originally posted by XS650:

quote:

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Originally posted by labman:
So everybody is blithely going ahead and changing brake fluid without a shred of data that it is needed?

---

No, some people wait until the cylinders chew up the seals because of corrosion

---

Changing the fluid has no effect out between the O-rings and the boots where the problem is.

---

If you haven't run into pitting and corrosion in the wet part of brake cylinders, then you have been bullchitting us about your brake system experiance.

 

[Stooge]

I believe that most European and Japanese Maintenance Schedules indicate brake fluid "change and flush" every two years. Why not with American Cars? Looks like the "American" Big Three are more interested in keeping the published Maintenance Costs to a bare minimum without regard to the real facts that indicate the need for brake fluid changes for proper brake system operation and longevity.

Case in point - Chrylers used the Bendix 10 ABS system in many "near 1990" vehicles. The exact same system was used in many European car lines. Why the big "recall" and problem with this brake system; the same installed on many vehicles, but problematic on just the Chryslers. Yeap, you got it. They required a complete bleed and flush as "scheduled maintenance," and yes, was not indicated in Chrysler's Maintenance Schedule, to save on the published maintenance costs.

Change the fluid periodically, test it if you like, but still change it. The hydraulic system on your ride should last longer than your ride with proper maintenance.

 

[XS650]

quote:

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Originally posted by Stooge:
Change the fluid periodically, test it if you like, but still change it. The hydraulic system on your ride should last longer than your ride with proper maintenance.

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Is there any particular test your recommend?

My test is to take the cap off the MC, look at it and say "yup, two years was plenty of time on this fluid"

If I were to get serious about it, what would I be looking for? Sizzle on a hot surface? Ph change? What values?

I probably won't do it, but am interested in what an ambitous person would look for....just in case.

 

[labman]

pH is meaningless in a non ionic material such as brake fluid. To test for acid you would need to titrate it. How it sizzles might be a quick test for difference in water content.

As for pitting, it is quite common in the very bottom, often below the inlet where the fluid might not be flushed out. I never knew of a caliper becoming unserviceable due to pitting. Corrosion of the piston outside the O-ring is a common problem.