I have a 2019 Cx5, 2.5 not turbo. I tried to find the system brake fluid capacity and the capacity of the reservoir. I couldn’t find either? Rather than do a flush, which requires putting the car up on jack stands (which I don’t have, nor do I have a hydraulic jack) and removing all the tires, I have a different idea. The idea is to drain the fluid from the reservoir and replace with new fluid, then drive for a couple of days to mix the fluid, Then repeat that process multiple times. If I knew the total system capacity and the reservoir capacity (the latter I would know after the first time I extract it), I could mathematically calculate the number of times I need to repeat the process to replace (exchange) a large percentage, say 90%, of the old fluid. Is this idea reasonable or just plan wrong?

 

Poor idea. There will be very little if any “mixing” of the new and old fluid in the closed brake system. The old fluid in the lines is what needs to be replaced, particularly close to the calipers where the fluid gets the hottest. And that’s why a brake flush is required.

 

BAD IDEA, nice theory but.......................

This is a great thought, but it would take months or more and thousands of miles while frequently using the brakes under different braking conditions of driving to do even a slight bit of a dilution mix and change. However, changing the revivor is not a bad idea. It will at least keep fresh brake fluid there. I might add that when you remove the fluid from the reservoir to wipe it with a clean lint free rag before adding new fluid. Keep in mind your ABS hold fluid in its parts longer than the rest of the system and that's why you really should do a complete fluid replacement at least on the service scheduling recommendation. Alway read the ABS service procedure in advance so you don't adversely affect the ABS and get a brake light and then must have a service shop correct the oversight during a full fluid flush and replacement.

 

It's "supposedly" 12oz but it is going to vary.
You can do it using a syphon pump but there's no guarantee you'll get all the old fluid out and if you don't it's really not worth the effort.
It's really not that expensive to have it done correctly in the shop, especially if you go a brake service specialty shop.
Some people never change it, some change it yearly, Mazda says 50K-100K, my Mazda shop recommends a change at 30,000 miles.
They'll do mine at my next service as they will be doing pads and tire rotation as well it will cost me an extra $100.

 

You can have the fluid tested or do it yourself?

Post # 94

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@CarpeDiem @Callisto @Lobstah Thanks for the replies. When I need to do it, I’ll just have it done at a shop and make sure I’m getting a full fluid replacement including bleeding the lines.

 

I see that you have several Firestones in your area. You may check and see if they offer a FREE fluid condition check?

 

The brake fluid condition check was something I was not aware of until several years ago when I took my Tacoma to an indie shop for a brake fluid flush. They took my truck back and returned with it a short while later telling me I didn't need to have the fluid changed after checking it. No charge. I was suitably impressed as it was first visit at that shop. I purchased an electronic meter recently to do this myself.

 

I love/hate the electronic brake fluid meters that people use. mainly because they do not clean them properly after using them which effects the results of the next follow-up testing. I have strip tested a customer's brake fluid and it shows getting close or needing a fluid replacement and a customer stating testing the fluid and it was fine. So, when I ask the customer to clean the probe end with Isopropyl alcohol let it dry and then wipe with a clean lint free cloth and have them self-retest, they come up with the results I got from the test strips.
So just keep that in mind when using them, thoroughly clean them after you test your brake fluid.

ASE

 

The testers conductivity/boiling point/strips are measuring only in the brake fluid in the reservoir not what's in the lines or your calipers.
Both can give some piece of mind but in reality, you cannot know for certain your "complete" brake fluid condition without a measurement from the reservoir and each caliper bleeder.
I'll use drinking water as an example: You can have well or public water that test fine but when tested at one of your taps can have lead or other containments.
And if you are going to test each caliper you might as well change the fluid out.