Testing Brake Fluid
 

I read that I can determine the moisture content of the brake fluid in my
car
by using a DMM (digital multimeter). Negative lead to the -battery term
and the positive lead to the brake fluid in the reservoir. Anything
below .3 volts is acceptable.
Any comments on the validity of this method?

Testing Brake Fluid
 

On Jun 22, 3:07*pm, "ED" > wrote:
> I read that I can determine the moisture content of the brake fluid in my
> car
> by using a DMM (digital multimeter). Negative lead to the -battery term
> and the positive lead to the brake fluid in the reservoir. Anything
> below .3 volts is acceptable.
> Any comments on the validity of this method?

That would vary wildly depending on the multimeter. Completely
unreliable. Google brake-chek for a german optical tester.

Testing Brake Fluid
 

"ED" > wrote in :

> I read that I can determine the moisture content of the brake fluid in
> my car
> by using a DMM (digital multimeter). Negative lead to the -battery
> term and the positive lead to the brake fluid in the reservoir.
> Anything below .3 volts is acceptable.
> Any comments on the validity of this method?
>
>



Trying to avoid getting the fluid changed?


--
Tegger

Testing Brake Fluid
 

On 06/22/2011 12:07 PM, ED wrote:
> I read that I can determine the moisture content of the brake fluid in my
> car
> by using a DMM (digital multimeter). Negative lead to the -battery term
> and the positive lead to the brake fluid in the reservoir. Anything
> below .3 volts is acceptable.
> Any comments on the validity of this method?
>
>

in theory it could work, but it depends on the electrode metal and the
type of metal the cylinder is made of. cast iron has a different
electrode potential to aluminum, which has a different potential to
stainless, which has a different potential to chrome plated brass, which
has a different potential to only partially chrome plated brass, etc.
so, unless you know the potentials for your probes and your system
respectively, or you use a specific known probe calibrated for the
system you're testing, you're completely in the dark.


--
nomina rutrum rutrum

Testing Brake Fluid
 

In article >, ED > wrote:
>I read that I can determine the moisture content of the brake fluid in my
>car
>by using a DMM (digital multimeter). Negative lead to the -battery term
>and the positive lead to the brake fluid in the reservoir. Anything
>below .3 volts is acceptable.
>Any comments on the validity of this method?

Problem is that this is very dependant on the electrodes being used.
If you had a couple standard electrodes, though, you could do it accurately.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Testing Brake Fluid
 

"Scott Dorsey" > wrote in message news:itvfi1>
> Problem is that this is very dependant on the electrodes being used.
> If you had a couple standard electrodes, though, you could do it
> accurately.
> --scott
> --
I dont think even that would help this method, Scott.

The most accurate method I know of for water in polyols is Karl Fischer
titration....and that is beyond the cost limitations and technology of most
people who want a value for water in polyols.

There are some test strips:
http://www.gwrauto.com/stripdip.htm

that may be economical for shop use.

Discussion:
http://brakefluidtest.com/news/speci...vs-water.shtml

Testing Brake Fluid
 

On 06/23/2011 07:17 AM, hls wrote:
>
> "Scott Dorsey" > wrote in message news:itvfi1>
>> Problem is that this is very dependant on the electrodes being used.
>> If you had a couple standard electrodes, though, you could do it
>> accurately.
>> --scott
>> --
> I dont think even that would help this method, Scott.
>
> The most accurate method I know of for water in polyols is Karl Fischer
> titration....and that is beyond the cost limitations and technology of most
> people who want a value for water in polyols.
>
> There are some test strips:
> http://www.gwrauto.com/stripdip.htm
>
> that may be economical for shop use.
>
> Discussion:
> http://brakefluidtest.com/news/speci...vs-water.shtml

there aren't many modern vehicles with brass brake componentry -
"copper" is just something to get the ignorati worried about so they pay
for more diagnostics and the service industry concerned that they "don't
get left behind" and buy new equipment.

as for test strips, they're ancient history.

<http://www.otctools.com/products/brake_fluid_safety_meter>

<http://www.bestbuyautoequipment.com/Storm-by-Central-STO3S121-p/sto3s121-01.htm>


--
nomina rutrum rutrum

Testing Brake Fluid
 

hls > wrote:
>"Scott Dorsey" > wrote in message news:itvfi1>
>> Problem is that this is very dependant on the electrodes being used.
>> If you had a couple standard electrodes, though, you could do it
>> accurately.
>
>I dont think even that would help this method, Scott.

It's true that there's other stuff that will increase conductivity, but I
think everything that will possibly increase conductivity is going to be
something you probably don't want in your brake lines.

But, unless you have calibrated electrodes and a calibrated volume,
you can't get resistivity from resistance.

>The most accurate method I know of for water in polyols is Karl Fischer
>titration....and that is beyond the cost limitations and technology of most
>people who want a value for water in polyols.

That seems severe overkill for the application, and definitely not an
easy kitchen job.

>There are some test strips:
>http://www.gwrauto.com/stripdip.htm
>
>that may be economical for shop use.

Frankly, it seems easier to change it than to test it, although I realize
some newer vehicles with ABS systems can make it more difficult to change.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Testing Brake Fluid
 

On 06/23/2011 08:00 AM, Scott Dorsey wrote:
> > wrote:
>> "Scott > wrote in message news:itvfi1>
>>> Problem is that this is very dependant on the electrodes being used.
>>> If you had a couple standard electrodes, though, you could do it
>>> accurately.
>>
>> I dont think even that would help this method, Scott.
>
> It's true that there's other stuff that will increase conductivity, but I
> think everything that will possibly increase conductivity is going to be
> something you probably don't want in your brake lines.
>
> But, unless you have calibrated electrodes and a calibrated volume,
> you can't get resistivity from resistance.
>
>> The most accurate method I know of for water in polyols is Karl Fischer
>> titration....and that is beyond the cost limitations and technology of most
>> people who want a value for water in polyols.
>
> That seems severe overkill for the application, and definitely not an
> easy kitchen job.
>
>> There are some test strips:
>> http://www.gwrauto.com/stripdip.htm
>>
>> that may be economical for shop use.
>
> Frankly, it seems easier to change it than to test it

ain't that the truth. while i'll take testing over superstition every
time, brake fluid, with its attendant seal swelling/degradation
problems, and known absorption profile, is simply not worth it - just
change every other year. testing may be useful for shops where they
have a new customer and an unknown service profile, but for an owner
that knows their vehicle's history, it's pointless.


> , although I realize
> some newer vehicles with ABS systems can make it more difficult to change.

that may have been the case when they first came out, but these days,
it's really not a problem.


> --scott
>


--
nomina rutrum rutrum

Testing Brake Fluid
 

"Scott Dorsey" > wrote in message
...
> hls > wrote:
>>"Scott Dorsey" > wrote in message news:itvfi1>
>>> Problem is that this is very dependant on the electrodes being used.
>>> If you had a couple standard electrodes, though, you could do it
>>> accurately.
>>
>>I dont think even that would help this method, Scott.
>
> It's true that there's other stuff that will increase conductivity, but I
> think everything that will possibly increase conductivity is going to be
> something you probably don't want in your brake lines.
>
> But, unless you have calibrated electrodes and a calibrated volume,
> you can't get resistivity from resistance.

This is true. Conductivity or resistivity measurements will respond to
various types of contaminants in the brake fluid, to temperature, etc.
But maybe you dont really need a very accurate measurement.

I think it would be cheaper and better just to flush out the old
stuff and replace every couple of years.

I still have that #@& Reatta that has the very special braking system.
If you dont flush that one every couple of years, you get to buy a new
or rebuilt master cylinder, which - last I heard - cost the better part
of a couple of grand.