Checking Brake Fluid With A VOM Meter

[wcurtin1962]

Something I learned the other day:

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

 

 

[Ray,IN]

How does that work with today's plastic containers?

[sundancer268]

Only the reservoir is plastic, the Master Cylinder is Aluminum or Cast Iron and normally is what the plastic reservoir is mounted on.

[oldjohnt]

While I don't doubt the basic science involved, it just seems to me there are soooooooooo many variables (not even talking about meter accuracy at those levels) involved  its hard to place one single "number" on what volts accurately indicates what's acceptable or not, but hey I haven't studied this at all so heck it may be right on ?? When I buy an RV and intend to use it for my own travels I typically drain and flush the entire system and replace the brake fluid all together REGARDLESS of what any voltage test might indicate. Its not all that hard or expensive. But that's just me and in my DNA lol to each their own ……..If this method works for you hey go for it.....

John T

[Kirk W]

22 minutes ago, oldjohnt said:

When I buy an RV and intend to use it for my own travels I typically drain and flush the entire system and replace the brake fluid all together

I agree with this and I also do that about every 5 years. When using a meter, even if the process works, readings of less than 1V are not all that accurate with the cheaper meters that most RV folks own. Until you get up to something like a Fluke 77 or higher, I would not trust the reading to be accurate and even the 77 needs to be checked for accuracy frequently. When I worked in field service, we checked our meters against a known standard once every quarter and records were kept to make sure that happened. 

[wcurtin1962]

The point of ground doesn't matter, I found a website that said to use the negative battery terminal. As far as meter accuracy, a base line can be recorded when the brake fluid is changed and using the same meter periodically. This can be used with coolant as well. I grounded the meter on the radiator support and got an 0.7 volt reading in the plastic radiator of my Ranger which is in need of a coolant flush. I got a .21 reading on the brake fluid of my Ranger which was mostly changed last winter when I blew a axle line. There are also testers on Amazon between $10  to $20  but since I already have VOMs it doesn't make sense to buy another tool.    

[Ray,IN]

This question is moot anyway, virtually all vehicle with hydraulic brakes, maintenance schedules say to change brake fluid annually.

[mptjelgin]

11 minutes ago, Ray,IN said:

This question is moot anyway, virtually all vehicle with hydraulic brakes, maintenance schedules say to change brake fluid annually.

WHAT?? 

I've owned three new Ford Superduty trucks since 1999, the latest being the new 2019 that I picked up in November. There is no service interval at all on the brake fluid. In fact, the recommendation is that since it is a sealed system there is no reason to ever flush/change the fluid absent some specific problem. I owned the first two trucks for a cumulative 20 years and 320,000 miles without ever opening the brake system.Same service with several other vehicles.

I would like to see an example of a modern vehicle with a factory maintenance schedule calling for brake fluid to be changed annually. 

 

[oldjohnt]

Hey, call me old fashion, call me a worry wart, call me a preventive maintenance nut, just don't call me late for supper lol

But for me REGARDLESS of what any owners manual recommends,,,,,,,,REGARDLESS of what any voltage test indicates, anytime I buy a used vehicle and every few years of ownership thereafter I DRAIN AND FLUSH AND REFILL (then bleed of course) BRAKE FLUID and plan to continue to do so (I do likewise with coolant). I have changed it before and despite it being a closed system, and despite how well it may or may not be sealed THE OLD FLUID IS USUALLY DISCOLORED AND THERE APPEARS TO BE SOME SORT OF VISIBLE "CONTAMINATION" that I DO NOT see in the new fluid ??? even though I never had it analyzed. Heck it may be perfect or better then new, I don't really care as long as it is discolored and I can see some of what I describe, for lack of a better term "contamination",  I'ma changing yayyyyyyyyyyy lol  Ive NEVER had any problems doing that, owned RV's for 48 years... Now don't ask me to describe or analyze what I call "contamination" I'm saying the old never appears as clean and clear and totally free of "something" as does the new !!!!!!!!!!!!!! Is it rust?? Is it moisture?? Is it foreign material?? Its for sure "something" noticeable to the eye...……...

 That's my story and Ima stickin to it lol but to each their own choices be it justified or not. It would be a boring world if all us RVers had the same opinions...……..

 Old fashion preventive maintenance kinda guy   John T

[Kirk W]

2 hours ago, mptjelgin said:

I've owned three new Ford Superduty trucks since 1999, the latest being the new 2019 that I picked up in November. There is no service interval at all on the brake fluid.

I read this and thought that I knew otherwise, so I just checked my Dodge, diesel truck and my Kia SUV. Both books do address checking brake fluid and replacing "as needed" and both clearly state what fluid should be used. Neither owner's manual mention and interval to replace the brake fluid. I would have sworn that our Ford chassis manual for the class A that we lived in suggested replacing the brake fluid every 3 years, but now I'm not so sure. I know that loss of braking due to moisture in the fluid changing to steam in heavy brake use was a concern at one time. My chassis was a 1999 F-53. It could have been information from the chassis hotline as I did talk with them and also with a Ford rep at the Dallas RV show. I know that I did a complete replacement of fluid several times in the 14 years we owned it. 

Thinking about it, the replacing of fluid may have come from a seminar at Escapades or Good Sam rallies or some similar place. 

[mptjelgin]

Ask yourself this simple question:  In a modern, sealed braking system, how is the brake fluid going to absorb water? I too had old 60's era automobiles and trucks that had issue with moisture, rusting wheel cylinders, etc. but they also had exhaust systems that rusted out and plugs that needed to be changed fairly often. Not only have the brake fluids changed significantly, but the materials in the master cylinders, reservoirs, etc. are different as well. 

Modern vehicles are very different and  in many cases there is no need to carry forward old maintenance techniques and practices. 

I am also a "preventative maintenance nut" but some things need to be done and some don't. I could argue that opening up a sealed system that requires no maintenance and "maintaining" it is just as likely to cause an issue as prevent it. 

 Once again: Can anyone show me a maintenance schedule for a modern vehicle that recommends changing brake fluid annually, or even as a scheduled maintenance item?

[Kirk W]

1 hour ago, mptjelgin said:

Can anyone show me a maintenance schedule for a modern vehicle that recommends changing brake fluid annually, or even as a scheduled maintenance item?

The Dodge in my last post is a 2003 model and the Kia is a 2009 model. If I remember accurately, it was there in 1999, but even that is sketchy. Do not brakes still have bleeders at each wheel?  I'm guessing that it is probably a combination of the improvement in brake fluids (which I have been aware of for some time) and perhaps the systems used to leak air and no longer do so? The only place under ideal circumstances that air might enter would be the fluid check and fill openings, I would think. But I'm not much of a mechanic so there could be far more to it than I think. 

[57becky]

This is a discussion on brake fluid changes that hits some good points, and has a good compromise on replacement when there is little guidance from the manufacturers.   https://www.cars.com/articles/2013/12/does-brake-fluid-need-to-be-changed/

[oldjohnt]

Just to clarfify something, the old brake fluid I spoke of (when I perform a flush n fill) that was discolored and contained some sort of visible "contaminants or foreign material" was that which came out at the wheel cylinders or calipers, not the up front reservoir. In addition to changing brake fluid (new/used vehicle and every few years thereafter) I also change coolant and flush n fill n change tranny fluid and filter around 50,000 or so miles.   

 Id be surprised if EVERY manufacturers owners manual offered the very same suggestions when it comes to changing or never changing brake fluid, but due to over the year improved products and the "contaminants or foreign material" whatever it may or may not be, if harmless or not, I'm sticking with changing brake fluid along with coolant and tranny fluid etc. as part of periodic maintenance, but as always respect those who choose for whatever reason, scientifically justified or not, to change or never change any fluids anytime they wish lol

 Keep safe yall best wishes n God Bless

John T  Dry camped coming to you live from South Padre Island    

[Ray,IN]

excerpt from   https://www.mainlandford.com/blog/ford-f150-scheduled-maintenance-guide/

2017 Ford,

Brake Fluid:

Why you should check: Brake fluid is one of the most important components of your brakes. It’s what makes the brakes themselves work, in that it uses the fluid to compress the pistons on the brake rotors, allowing your F-150 to stop when you need it to. The process of changing your brake fluid is a rather involved task, and is not recommended for amateur mechanics – particularly as properly working brakes are such a critical component of a working vehicle.

• Check your brake fluid level on a bi-weekly basis, using the markings on the reservoir.
• Add fluid as necessary, referring to your F-150’s owner’s manual for type.
• Change your Brake fluid every 50,000 to 80,000 kilometers
  • Changing your brake fluid requires a socket set, screwdrivers, rubber tubing, a drain bucket, and an assistant to help out.

On 12/3/2018 at 3:54 PM, mptjelgin said:

WHAT?? 

I've owned three new Ford Superduty trucks since 1999, the latest being the new 2019 that I picked up in November. There is no service interval at all on the brake fluid. In fact, the recommendation is that since it is a sealed system there is no reason to ever flush/change the fluid absent some specific problem. I owned the first two trucks for a cumulative 20 years and 320,000 miles without ever opening the brake system.Same service with several other vehicles.

I would like to see an example of a modern vehicle with a factory maintenance schedule calling for brake fluid to be changed annually. 

 

It is also plainly stated in the 2002 Chevrolet K3500 owners manual I owned.

 

[mptjelgin]

1 hour ago, Ray,IN said:

excerpt from   https://www.mainlandford.com/blog/ford-f150-scheduled-maintenance-guide/

2017 Ford,

Brake Fluid:

Why you should check: Brake fluid is one of the most important components of your brakes. It’s what makes the brakes themselves work, in that it uses the fluid to compress the pistons on the brake rotors, allowing your F-150 to stop when you need it to. The process of changing your brake fluid is a rather involved task, and is not recommended for amateur mechanics – particularly as properly working brakes are such a critical component of a working vehicle.

• Check your brake fluid level on a bi-weekly basis, using the markings on the reservoir.
• Add fluid as necessary, referring to your F-150’s owner’s manual for type.
• Change your Brake fluid every 50,000 to 80,000 kilometers
  • Changing your brake fluid requires a socket set, screwdrivers, rubber tubing, a drain bucket, and an assistant to help out.

It is also plainly stated in the 2002 Chevrolet K3500 owners manual I owned.

 

Nice Try.  You've quoted a dealers blog. Hardly a definitive source.

The Ford Owners Manual and Maintenance Schedule for the 2017 F-150 referenced in your quote has no recommendation for changing brake fluid. None. It simply says that the fluid level should be between the MIN and MAX lines and to keep the reservoir cap in place and tight to avoid contamination. There is a reason that the reservoir is clear, so that you don't have to open the cap. 

And with all due respect, your 2002 K3500 is a 17 year old vehicle, so hardly qualifies as a modern vehicle. But I did find a manual online for the 2002 GMC C/K 2500/3500 series of trucks and it contains only wording regarding keeping the brake fluid between the MIN and Max lines of the clear reservoir. No flush/change interval noted in that manual either...

What you stated was "This question is moot anyway, virtually all vehicle with hydraulic brakes, maintenance schedules say to change brake fluid annually." And I asked if there was an example of a modern vehicle factory maintenance schedule that reflected that statement. So far the answer is no.

[Ray,IN]

2 hours ago, mptjelgin said:

Nice Try.  You've quoted a dealers blog. Hardly a definitive source.

The Ford Owners Manual and Maintenance Schedule for the 2017 F-150 referenced in your quote has no recommendation for changing brake fluid. None. It simply says that the fluid level should be between the MIN and MAX lines and to keep the reservoir cap in place and tight to avoid contamination. There is a reason that the reservoir is clear, so that you don't have to open the cap. 

And with all due respect, your 2002 K3500 is a 17 year old vehicle, so hardly qualifies as a modern vehicle. But I did find a manual online for the 2002 GMC C/K 2500/3500 series of trucks and it contains only wording regarding keeping the brake fluid between the MIN and Max lines of the clear reservoir. No flush/change interval noted in that manual either...

What you stated was "This question is moot anyway, virtually all vehicle with hydraulic brakes, maintenance schedules say to change brake fluid annually." And I asked if there was an example of a modern vehicle factory maintenance schedule that reflected that statement. So far the answer is no.

You said you would like to see an example, I copied N pasted it for you. I suppose you would not believe your dealers website either. You do not believe me, I don' believe you. End of conversation.

[mptjelgin]

20 minutes ago, Ray,IN said:

You said you would like to see an example, I copied N pasted it for you. I suppose you would not believe your dealers website either. You do not believe me, I don' believe you. End of conversation.

I am puzzled. What exactly have I stated that you don't believe?

Do you still believe " This question is moot anyway, virtually all vehicle with hydraulic brakes, maintenance schedules say to change brake fluid annually"? 

As Daniel Patrick Moynihan said, "Everyone is entitled to his own opinion, but not to his own facts" and that applies here. 

[Scrap]

For Hydromax and Hydromax II (medium duty trucks have em, probably RV's, etc) you go by TMC TP 1409.  It is not in the owners manual because it is industry standard thing.

I don't do automotive, but they did an industry standard in the mid-2000's.  It goes by amount of copper.  There's test strips for it.  I know it is for DOT3 sealed (bellows) cap, not sure if it is vented DOT4 european.  I'm sure it is all Google-able.

[Carlos]

Quote

I would like to see an example of a modern vehicle with a factory maintenance schedule calling for brake fluid to be changed annually. 

I've never heard of annually, but our BMW says to change it every other year.  Probably still overkill in our climate (AZ), so now that it's off warranty, I'll probably do every three years as I do with the Jeep (and every other vehicle).  Unfortunately the computer still lights up a warning at 24 months.

 

[rls7201]

Ford F53 owners manual up to and including 1997, clearly states to change the brake fluid every 2 years.

Brake fluid is hygroscopic, and moisture will very slowly get past the seals and into the brake fluid.

[oldjohnt]

Very informative thread. Looks like "some" owner manuals call for brake fluid change while others are silent on the subject. As long as my owners manual doesn't specifically state one should NOT ever change it and/or reasons why its harmful or destructive (for whatever reasons)  I'm going to continue the practice of a good flushing and replacement (if and as needed) BUT TO EACH THEIR OWN CHOICES …..You know well some have NEVER changed it and never had a problem, but likewise, many like me have changed it (new fluid was a lot cleaner and foreign material and contaminant free) and never had a problem either ???? 

Happy New Year yall

John T   live from Cracker Barrell parking lot in Crestview Florida  

[Carlos]

Brake fluid and trans fluid seem to be most neglected.  Changing both of those regularly would reduce repair costs for people, sometimes by a lot.