Corrosion protection in brake fluid

[Barnaclebob]

How does the copper corrosion protection in brake fluid work? My understanding is that as the fluid absorbs water it becomes more acidic or corrosive and the corrosion protection gets used up to cancel this out and copper is left behind for the stips to detect.

So if brake fluid still has acceptable copper levels can it still have too low of a boiling point due to water absorption?

Basically I'm trying to determine if I need to buy a refractometer in addition to the test strips to test my brake fluid.

 

[Yah-Tah-Hey]

Just replace brake fluid every two years.

 

[slacktide_bitog]

Flush it every few years. Speed bleeders are awesome

It's not the boiling point that matters as much as the percentage of moisture, which is what your test strips measure.

 

[Barnaclebob]

Originally Posted By: slacktide_bitog
Flush it every few years. Speed bleeders are awesome

It's not the boiling point that matters as much as the percentage of moisture, which is what your test strips measure.


This may not be directly true and that's what Im trying to figure out. My understanding is that test trips directly measure the amount of copper in your brake fluid which indicates how much corrosion protection is left and indirectly how much water may be in the fluid.

Replacing every two years may not be necessary.

I have also tried the multimeter voltage measurement but cant find good documentation behind it so I don't want to trust it at this point.

 

[Oro_O]

If you are in the PNW on the "wet" side, it's a fool's errand to try to stretch it out more than 2/3 years if protection is part of your goal. The humidity, rain, and constant warm temperatures relative to most places year-round make it wear brake fluid as fast as any place.

It really doesn't matter if it's garaged or not IME. 2 to 3 years is the max I can go w/o detecting excessive water and worn fluid. It seems regardless of vehicle and if it's garage, outdoors, driven 5k/year or 15k, one year is overkill, 2 is good, 3 is acceptable in this environment.

 

[Barnaclebob]

How are you detecting excessive water and worn fluid? Its a 2011 Altima with 60k and original fluid and it was between 20 and 30 ppm when I tested it last week so as long as my strip wasn't defective its still good for corrosion.

I'm trying to determine if it can pass the corrosion test but still fail for water %.

 

[Johnny2Bad]

I'm with the others around here, save the testing / overthinking and just change the fluid every 2 years.

Brake Fluid absorbs moisture from the atmosphere, there is no storage regimen aside from perhaps storing in a gas-tight enclosure that will prevent moisture- related breakdown.

"Partly Aged" fluid still suffers from moisture- related degradation. One effect is *any* amount of moisture lowers the boiling points so only fredh fluid from a sealed container performs at 100%.

I suppose if moisture absorption was the only concern you could switch to Silicone Fluid but the changeover is not trivial (compatibility of components / seals).

 

[Bill_G]

+1 on speed bleeders

If you are concerned about your brake fluid, just get some speed bleeders for 7 bucks each and flush the fluid when you replace the pads or every two years, whichever comes first. Once the wheels are off, you can flush the whole system by yourself in 5-10 minutes.

 

[Trav]

A paper on it.

http://www.brakebleeder.com/brake-fluid-white-paper-on-copper/

 

[Johnny2Bad]

Been using Speed Bleeders for a decade, work awesome.

You can buy them from the usual "performance" brands (Russel, Earl's, etc) but they are cheaper and with a greater parts list from the manufacturer.

I recommend ponying up for the Stainless Steel versions, brakes are corrosion-magnets and the bleeders are just as prone to damage as any "regular" bleeder screw.

Speedbleeders.com

 

[Barnaclebob]

Originally Posted By: Trav
A paper on it.

http://www.brakebleeder.com/brake-fluid-white-paper-on-copper/


Thanks, this is the type of information I'm looking for.

It seems that the copper test is adequate for corrosion protection but says nothing about water absorption. Now the question is why my 5 year old brake fluid only tested at 20-30ppm. I did have to top it up a little bith a year ago because the brake warning light was coming on when the fluid wasn't past the low line, there was a service bulletin about this, no worries about leaks.

 

[Bill_G]

Originally Posted By: Barnaclebob
Originally Posted By: Trav
A paper on it.

http://www.brakebleeder.com/brake-fluid-white-paper-on-copper/


Thanks, this is the type of information I'm looking for.

It seems that the copper test is adequate for corrosion protection but says nothing about water absorption. Now the question is why my 5 year old brake fluid only tested at 20-30ppm. I did have to top it up a little bith a year ago because the brake warning light was coming on when the fluid wasn't past the low line, there was a service bulletin about this, no worries about leaks.



I guess I don't understand why you are putting so much time and effort into chasing this info and you apparently did not want to put out a few bucks and put fresh brake fluid in your car - it's a head scratcher to me.

 

[Lubener]

Originally Posted By: HosteenJorje
Just replace brake fluid every two years.


Exactly. Why screw around. One hour and you can bleed the whole system and be done with it.

 

[Barnaclebob]

Its not that I don't want to spend time or money. I'd be willing to buy a refractometer which will cost a car's lifetime of brake fluid changes. You'd be laughed at in the oil forum for saying to change your oil at 3000 miles just because its whats recommended and why mess around.

There are ways to test brake fluid and I want to make sure that if my fluid passes those tests that it is indeed safe.

I really like knowing the reasons and data behind why maintenance is required at various intervals.

 

[Lubener]

Brake fluid is designed to attract moisture so the only way to prevent internal brake system corrosion is to bleed the old fluid out.

 

[Trav]

Originally Posted By: Barnaclebob

I really like knowing the reasons and data behind why maintenance is required at various intervals.


Nothing wrong with that. I found the article interesting.

 

[GMorg]

The copper test will tell you about whether the fluid needs to be replaced due to exhaustion of oxidation inhibitors. Glycol ethers are corrosive to copper. In a sense, the copper tests are reporting on a history of heat and oxygen.

Moisture contamination is also a problem that can involve oxidation. However, the short-term issue with water is that it lowers the boiling point of the fluid.

For those that think that ignorance is bliss, please proceed and share your happiness. For those that want to understand the world around them, please proceed and share your knowledge.

 

[MolaKule]

Originally Posted By: GMorg
The copper test will tell you about whether the fluid needs to be replaced due to exhaustion of oxidation inhibitors. Glycol ethers are corrosive to copper. In a sense, the copper tests are reporting on a history of heat and oxygen.

Moisture contamination is also a problem that can involve oxidation. However, the short-term issue with water is that it lowers the boiling point of the fluid.

For those that think that ignorance is bliss, please proceed and share your happiness. For those that want to understand the world around them, please proceed and share your knowledge.


Excellent!

 

[Barnaclebob]

Is there any way that my fluid could test at such low copper levels ~30ppm after over 4 years in service from the factory? That has me scratching my head.

Since I now have a mixture of mostly DOT3 and a little DOT4 i may just replace it because I can't use a refractometer to determine moisture content anyway.

 

[Benito]

Based on what GMorg is saying, it would appear that the formulation of corrosion inhibitors could result in lower copper readings than expected.

It is still not clear to me if that means there is a potential danger to the system's longevity from higher moisture as opposed to "just" an increased danger of reduced braking performance.