Hi Scotti
I have a 2021 Sorento. I recently brought it to a local "XXX" tire place for the state mandated annual inspection. They told me my brake fluid was contaminated. They recommended a brake flush. I declined. Using a syringe I pulled the fluid out of the brake reservoir and replaced it with fresh DOT4 as per the owners manual. The fluid that came out was clear with a amber tint while the new fluid was clear. I have a moister tester and it read OK. The car has 37K and the brakes seem to work fine both before and after the new fluid. I will bleed the brakes next spring when things warm up in New York. Should I be concerned? What is the typically life of brake fluid?
Some people never change brake fluid and seem to do OK, but I think in the long run you'll have fewer hydraulic system problems if it is changed out periodically. You should be able to get at least 4 or 5 years out of the fluid. I'd say the "tire place" was trying to rip you off.
That tire place was trying to rip you off. DOT 4 is an alcohol-based fluid and it will absorb water vapor if left exposed to the ambient air for too long (a matter of hours if you live in Ohio). Even bottles that have had their seals broken have a limited shelf life. That depends on where you live. In the enclosed space of a brake line, water vapor still slowly contaminates the brake fluid over many years, turning it from clear-amber to black if you're naughty and never change the brake fluid. Sealed brakes should last longer than three years, if you don't live in Cambodia or something.
The whole idea of changing brake fluid periodically is because of the heat that is generated during braking. DOT 4 has a much higher boiling point than ordinary water, and if you ride the brake going down a long, steep hill, etc. you may notice the brakes will start to become mushy -that's the accumulated water that's boiled. This can lead to brake fade and your car will take a longer time to come to a stop vs uncontaminated brake fluid -unsafe. I think most brake lines are still steel, and they will start corroding from the inside if you're dedicated to doing as little maintenance as possible.
In short, brake fluid doesn't need changing every 3 years. Take your moisture tester and test the brake fluid every 6 months to a year. That's very handy to have.
I am always suspicious of a flush. It implies some cleaner is introduced and then withdrawn and then the new brake fluid is added. How do you know you got all the cleaner out.
Thanks for the insight into brake fluid contamination.