Here are the latest reader Question, along with my Reply:
VZ asks: Hi Eric – the last couple of years it seems that the auto manufacturers, dealers, and other “experts” have been telling me I need to flush my brake fluid and refill with new every couple years. Their reasoning is that since brake fluid is hygroscopic, it absorbs moisture, and over time that moisture contaminates, changes the boiling point, and does other nasty things to the fluid that create a situation that’s not saaaaafe! Couple things come to mind. First, isn’t the brake hydraulic system a closed system? I don’t understand how air, water, or whatever could enter in the first place – assuming no leaks or defective parts. Second, empirical observation. I’ve been driving and wrenching for 50 years and have owned several dozen cars. Many of them were north of 15 – 20 years old, and I’ve never changed brake fluid on a single one. Nor did I ever know anyone that did. Never had a fluid related issue in my life. On the other hand, I plan to keep my current truck till the day I die, so I don’t mind doing whatever maintenance is necessary to keep it running (and stopping!) that long. So, anyway Eric, what are your thoughts? Is this just another way for the auto industry to extract money from the serfs, or should I really be doing it once in awhile?
My Reply: On this one, I am in agreement with the “experts.” Here’s why: Brake fluid does get contaminated/degrades over time; notice the change in color of the fluid in the reservoir. Moisture can get into the system in several ways, via the master cylinder reservoir, for instance. It is not a hermetically sealed system. Also, heat cycling takes its toll on the fluid.
Old, dirty fluid can lead to problems with calipers/wheel cylinders/the master cylinder itself as well as (in modern cars) ABS pumps – which are not cheap to replace. Braking performance can be affected as well and though I am not a high priest of the saaaaaaaaaaafety cult, I do believe in keeping brakes in good working order and in good maintenance protocols generally.
I bleed the brakes in my vehicles once a every two years. It’s a simple, inexpensive job and to me that makes it well worth doing, given that calipers, master cylinders and ABS pumps are not inexpensive and require a great deal more work to R&R.
PS: You can also short-cut this a bit by periodically using a syringe to suck out most of the dirty fluid in the master cylinder and then top off with fresh. This will replace about a third to half the fluid in the system with fresh fluid and extend changeout intervals a bit. But bear in mind there will still be older fluid farther down the lines and the entire system ought to be bled at least every several years.
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