Checking Brake Fluid With A VOM

[wcurtin1962]

Something I learned today:

Check for galvanic reaction
Remove brake fluid reservoir cap, and set the DVOM or multi meter to
read voltage on the lowest voltage range of the meter. Place one of
the
multi-meter probes into the brake fluid and the other against the body
of the master cylinder.
The voltage should be no greater than 0.3 volts.
If the voltage is higher this indicates a galvanic reaction which
means
there is an unacceptable level of moisture in the brake fluid.


https://media.supercheapauto.com.au/sca/images/articles/Repl_Brake_Fluid.pdf

 

[highdesertranger]

interesting never heard this before. but most newer vehicles have a plastic reservoir. also wouldn't an aluminum master have a different reading then a cast iron one? highdesertranger

 

[wcurtin1962]

I saw YouTube video with a tester being used that had two probes a half inch apart. That's when I tried searching for using a VOM meter to test brake fluid. So I would try sticking both leads in the fluid about a half inch apart or grounding to the body of the master cylinder.

 

[closeanuf]

?????????  Gotta be true if it's on youtube.

 

[highdesertranger]

of course. highdesertranger

 

[Weight]

Not producing current. Measuring resistance. You know, ohms. If there is that much water in the brake fluid it is too late.

 

[wcurtin1962]

No this is measuring volts on the lowest scale. Here's the tester I saw on YouTube:

https://www.amazon.com/eOUTIL-Autom...1543281575&sr=1-4&keywords=brake+fluid+tester

 

[Manyways2go]

My 2 cents
it's measures liquid and dissimilar metals which makes a battery of sorts.
Years past I have measured coolant in the radiator with a voltmeter too. My understanding was checking acidic content
so lower was better. Brake fluid absorbs water from the atmosphere and it lowers the boiling point with time.
It could cause brakes to fade in extreme circumstances.

So good maintenance  with brake fluid would be replace the brake fluid at intervals say 5yrs or 60,000miles
It sure looks better than dark ugly fluid, cleaning the plastic reservoir is another option
I don't - but always think  I will get around to it eventually.
There always seems to be plenty of needed repairs that take priority.

If changing coolant think about the age of the hoses (Radiator, heater and bypass)
If you take it to a shop ask for comments on these and use good judgement.
It has been my experience so many different opinions among the mechanics