Curiosity on brake fluid

[Starving Electrician]

Just as a curiosity what everyone's approach is to brake fluid swaps. I am not as religious on brake fluid as I am on other maintenance items. I generally do a full fluid swap when I change pads or shoes, or if I have the wheel off for some other maintenance such as struts or ball joints or the like. Just curious what other approaches there are.

 

[The Critic]

Every two years or 30k, whichever comes first for me.

 

[dubber09]

They sell cheapish water content testers and 2%-3% is a 'warning' zone while over 3% is a 'danger' zone with those. I normally get into 2% vicinity in 2-3 years and change BF then, but never run it longer than 3 years.

 

[rijndael]

You can use a multimeter too, it's a basic resistance check.

 

[harbor]

I was getting ready to flush the brake fluid on my 3 year-old Challenger, but the tester showed 1.4%, so will do it next year. Car is a garage queen with 7K miles, so that must account for the low reading.

 

[MasterSolenoid]

My Ford Escape service manual show every 3 years.
I do the work myself and it gets done every 2 years.

Brake fluid does not cost much, and I would not trust an inexpensive tester.
At 2 years old, the brake fluid is a 'straw' color.

 

[ATex7239]

I’m bad about this one. I do it when the brakes get done. I don’t top off the reservoir so when the fluid level gets around min I know it’s time to do the brakes.

 

[slacktide_bitog]

I usually do it with the pads and rotors.

 

[50yr Street Mech]

Every 2 years....bleed.bleed,bleed,bleed. Old school gravity style. 1 pint. You can feel a difference. Don't forget the little caps on the bleeders,,,,,or SNAP on the next go round.

 

[ripcord]

I don't think brake fluid gets changed that much. I took 4 gallons of waste fluid to my county hazardous waste station and the guy was amazed. I had to swear up and down that I was just a DIY guy and not a commercial mechanic before he would take it.

 

[eljefino]

I got one of those cheap pen testers and my fluid (in my climate/ humidity) takes 5 years or more to reach the first "not perfect" led. I change my fluid when I have to, of course, but when it visibly degrades to less-than-clear. Also when setting a fluid baseline on a new-to-me car.

It amazes me that some on bitog don't trust a cheap battery tester and go out to replace a perfectly good expensive battery, but will not trust a cheap pen tester for brake fluid and leave potentially terrible fluid in there. "It's cheap insurance".

 

[JimPghPA]

I flushed my 2016 CR-V by putting in 2 quarts of Bosch ESI6 - 32N, three years ago. I just checked it with an electronic test pen and test strips about a week ago, for the first time since I put that Bosch brake fluid in.

When I recently tested it, the electronic test pen showed zero ppm for moisture. The chemical test strip showed only 10 ppm copper, and the literature that came with those test strips says replace at 200 ppm or greater. 10 ppm is the lowest reading on the scale.

I was thinking of flushing it again before winter or next year. But it test extremely well. I have seen the cheap brake fluid test more than zero for moisture, new in a just opened bottle.

I'm just going to keep testing every year until it shows that it needs replaced.

Now I'm glad I spent the extra for the Bosch.

ESI6 stands for Extended Service Interval and I guess they threw on a 6 because 3 through 5.1 is already used. It's great brake fluid. No one had it local so I bought it off of Amazon.

Bosch claims that ESI6 can be used to replace 3, 4, and 5.1 and Bosch claims it last twice as long.

Next time I'll get it from Rock Auto. Amazon sometimes has fake stuff.

 

[JimPghPA]

I posted about this before:

Brake fluid has to be extremely hydro-scopic ( absorbe moisture into it, and its so hydro-scopic it will pull moisture right out of air ), because if it were not,moisture that gets in it from just the air, would condense out and accumulate in the low sections and cause rust.

Also, if theres enough moisture to cause water in the brake fluid, when hot enough it would turn to steam and push brake fluid back into the master cylinder. Then the next time someone applied brake, the fluid from the master would only compress the steam some, but never cause enough pressure in wheel cylinders to apply brakes.

Also, the brake line metal has some copper in it to make it bendable, and also not brittle enough to crack from vehicle vibration. The copper leaches out of the metal and into the brake fluid. The control housing for valves for the ABS is made of aluminum. And it has very small passageways for the brake fluid.

Aluminum and copper are on opposite ends of the chemical electro-negativity scale. Which means they can be used to make a battery. It also means combine brake fluid with copper and water and the aluminum of the ABS will corrode and be destroyed. And replacement of the aluminum valve and motor body of an ABS ain't cheap. And just getting all the air out can be difficult and eat up a lot of expensive mechanic time.

So, if moisture and or copper content of brake fluid gets too high, it needs replaced.

 

[troymcclure]

My Honda says every 3 years and my Nissan says every 2 years. I settled on every 3 for both because I like that number better and I don’t think fluid ages any differently in a Nissan than in a Honda.

Ive seen too many Amazon reviews of those cheap conductance testers reading fresh fluid as bad so I don’t use them. I go by time alone which probably means I’ll be doing more flushes than I need but the cost to DIY is so cheap. I believe Bosch sells a few types of conductance testers and they are hundreds of dollars and have a way to calibrate them so I don’t think the ones on Amazon can meet that standard.

Having a power bleeder makes doing it kinda fun. Always went with OE fluid, both of which are CCI DOT3, but picked up some of that ESI-6 and will try it out in the Nissan this month.

 

[Donald]

Speed bleeders and every two years or when you remember or get around to it.

You can tell I am very rigorous about brake fluid flush.

 

[Donald]

My Honda says every 3 years and my Nissan says every 2 years. I settled on every 3 for both because I like that number better and I don’t think fluid ages any differently in a Nissan than in a Honda.

Ive seen too many Amazon reviews of those cheap conductance testers reading fresh fluid as bad so I don’t use them. I go by time alone which probably means I’ll be doing more flushes than I need but the cost to DIY is so cheap. I believe Bosch sells a few types of conductance testers and they are hundreds of dollars and have a way to calibrate them so I don’t think the ones on Amazon can meet that standard.

Having a power bleeder makes doing it kinda fun. Always went with OE fluid, both of which are CCI DOT3, but picked up some of that ESI-6 and will try it out in the Nissan this month.

I have a Motive. It's still in the box. Speed Bleeders are too easy.

If a shade tree mechanic then a power bleeder like a Motive will waste brake fluid since whatever is leftover in the Motive probably gets dumped. If you use the Motive just for pressure then you need to take off the Motive adapter a few times to add brake fluid.

 

[willbur]

You can use a multimeter too, it's a basic resistance check.

I believe its a basic conductivity check. Looking for voltage, not ohms

 

[rijndael]

I'm not saying there isn't more than one way to do it:


https://patents.google.com/patent/US5028144A/en

And, you have this:






And:

https://toolsadvisers.com/how-to-check-brake-fluid-with-multimeter/

 

[JimPghPA]

I waited for a day when the humidity was low to do my recent fluid testing, Just opening and removing the screen, and replacing the screen and closing, replaces the air in the space above the fluid in the master, with ambient air. So its not something to do when the humidity is high.

 

[supton]

I used to every 2, but have not been sweating it lately. I tend to only keep cars for 10 years and I'm starting to think it's a bit overkill. YMMV. Plus once I started doing this, I noticed the brake fluid I get from Walmart likes to turn green, instead of just slowly turning dark. And it's never saved me from having calipers seize--contrary to opinion, I know, but from what I can tell, rust still takes out the caliper, from the outside in, regardless.