replace brake fluid- water or copper content

[Jake]

I am looking for best indicator of when to replace/ flush brake fluid. I understand hydroscopic property of brake fluid and what water can do to the fluid and components of brake system (tubing, calipers, pistons, ABS module, etc…). I have seen various pen-like testers on net and I think ETCG shows use of one. How accurate are they and IS presence of water THE best indicator to change fluid?
I have also seen, though less frequently, testers for copper in the fluid. higher copper content in fluid allegedly indicates corrosion of lining (Bundy Tubing). Is copper itself bad for the system or only an indicator that corrosion is occurring? I am assuming different make, models and age of vehicles will have different amounts of Bundy tubing or copper components. Hence, the same amount of copper in brake fluid from car “A” w/ very little copper components as car “B” w/ much more copper components, shows the corrosion in car “A” is much more advanced than in car “B”
I service five cars among my family. some are driven daily to sum of 30-35k annually; others sit and may be driven 2-3K annually. Changing the fluid is not the easiest/fun thing to do. I would like to keep this prevent maintenance task to “as needed” basis v. set interval w/o due regard to actual need. Yes, I do like getting Dirty, but doing it solo can be time consuming and “have a bad day” if I accidentally get air into the system. I know family should help and there are various tools for solo brake bleeding.
GREATLY appreciate you’alls responses.

Topic

[Nicholas Clark]

Let me come forward and say that I don’t know about a lot of the things that you have asked. So far as copper, bundy tubing, and testing. But what I do know is that changing fluid for a lot of people is taking MOST of the fluid out of the master cylinder is enough for a lot of people. I think Eric talked about that method in a video. It’s probably not the best way to change it but I think if you did it frequently enough it would be fine. When I say frequently enough, if you did that once a year it would be more often than I.

I don’t have a power bleeder, but when I “flush” my fluid I just pull most of the fluid out of the master cylinder — obviously not all the way, and replace that. I fill it up more than you’re supposed to and then bleed the lines a bit. It’s a backyard and maybe a “hack” way of doing things but I figure that’s going to get rid of at least 90% of the old stuff. By the time you get done bleeding the lines it needs more fluid anyway. Overfilling it is just insurance that I don’t bleed the master cylinder dry in the process. After the bleeding I top the master off to the PROPER level and that’s about it.

I do understand the significance of how a broken bleeder can ruin your day/week/put your car out of commission till you have time to source a new part and the time to fix it. I agree that when you are dealing with more than one or two vehicles there should be some kind of process for testing, because you don’t have that kind of time to waste. But I don’t test it. I just change it periodically. Usually I do that once every 5 years. I know people who have gone a lot longer without trouble. Mostly my dad, but I don’t trust his opinion on cars because he hates them. They are just an appliance to him anymore.

I know this wasn’t exactly responsive, but I thought some madness should go with the method.

[Paul]

I think the copper test is meant to be a quick litmus test of the brake fluid condition. It indicates that ethylene glycol has degraded, and the acidic products have corroded copper components in the brake system. BTW, copper can then further catalyze decomposition of the ethylene glycol, which increases the rate of decomposition of the fluid. Also, if the brake fluid contained corrosion inhibitors, the presence of copper indicates the inhibitors have been depleted.

The water content or the wet boiling point of the fluid is probably more important than the copper content because it’s directly related to the braking performance. I remember seeing a refractometer, where the simple handheld ones are fairly accurate (~5% ), that could estimate the water content of brake fluid.

I personally don’t perform either test and simply change the fluid at the specified time interval. I usually combine a flush with a tire rotation.
The crud seems to sediment at the bottom of the system, and the complete flush will remove it.

[Jake]

Thanks for the reply.
changing fluid in reservoir- Yes, some consider that a “brake fluid change” but it is half a job. the system is non-circulating so the fluid in the lines at the various components (calipers, lining, ABS, brake cylinder….) remains old/dirty/watered etc… I agree. It is better than nothing.

topping of fluid in master cylinder w/o installation of new pads/rotors, shoes/drums is not recommended by ETCG and other sites. the lowered fluid in master cylinder is one indicator that your pads are wearing down and will need replacement soon. hopefully, the wear indicator on rotor (causing screeching noise) will occur before all lining is gone and rivets start digging into rotor.
also, with some cars, as the fluid gets low it will cause and indicator light on your dash will go ON. The master cylinder top has a diaphragm that expands as fluid goes down to fill the void in the master cylinder and lessen the amount of air that introduces potential for moisture to mingle w/ fluid in the reservoir. topping off the fluid before changing pads/rotors, shoes/drums defeats both of these indicators of brake wear. Obviously, if you have a leak somewhere in the system, topping it off will prevent air or other disaster, but that is temporary stop gap until the leak can be located and component replaced.

[Jake]

Thank you for the reply.
Yes, the copper test strips (Phoenix systems at $60 a jar… worth it IF it works) is the only one I have seen, but there are a few different references to it.

I still am looking for information of accurately identifying when fluid needs to be changed. “with tire rotation” as you suggest, which I do every 6K, that is every other month on the highway (little braking) commuter car. with another vehicle that only is driven 2-3K/year, that tire rotation and fluid change is 24-36 months.

there has got to be a better way. :huh:

Thank you again for the detailed response.
Jake

[Christopher]

Yeah you can buy a quart of brake fluid at walmart for like $7.

[James]

Back before long-life coolant was the standard it was often recommended that brake fluid be changes out when the coolant was which was about every 2 – 3 years. Most people let the brake fluid go way longer than they should, it’s meant to be changed out at regular intervals.

[Brian]

The indicator I use is visual. If the system is leak free and sealed well, then you can go by the look of it. Clean fluid is clear. The dirtier it looks, the more rusty water there is in it. If it’s clear or mostly clear, then its fine. The inside of the resivior can look dirty, so draw a sample out with a turkey baster to see if it’s translucent. I flush it every 2-3 years on average.

[Rob Jorgensen]

Whether the vehicle is driven or sitting, the brake fluid still draws moisture. So, for me, the indicator is the calendar. I change mine every 2 years. It is cheap peace of mind.

[Jose Mari Gamboa]

Based on personal experience it is better to change once you spot something wrong with if its dirty or not natural as it was once was. I usually change mine between a year or two depends on how the car is being used 🙂

[Natasha]

[quote=”c918″ post=151271]Yeah you can buy a quart of brake fluid at walmart for like $7.[/quote]

Exactly. it takes me an 20 mins to replace the brake fluid with new. So early morning weekend and $10 and I’m done.

What’s all this measuring and hygrsocipic and litmus test and electric tester?

Why bother?

[Author]

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