Originally Posted By: Spartuss
Changing brake fluid every few years is a good idea that helps keep the system clean, moisture away and a good pedal response.
However, I was once advised against by a shop owner when I owned a '92 Subaru Legacy with 140k miles on the odometer that was on its original brake fluid. He told me to leave it alone as trying to mess with it at this stage in the game can push gunk further into the calipers causing problems. Any merit to this?
Not sure if this is was a coincidence, but last year I did a full brake flush on my '99 Nissan Maxima that I purchased used. The brakes were bled once in its life before this by the previous owner. A couple weeks after the full brake flush, one of my rear calipers began sticking and I was forced to change it. Once again, not sure if the stuck caliper was caused by the full brake flush, that caused gunk into the calipers.
Anyone?
Here are the tradeoffs. You decide.
Brake fluid is DESIGNED to absorb moisture. Moisture will get into the system from the atmosphere, and if it isn't absorbed it'll settle to the bottom of the calipers and cause rust.
Brake fluid that contains moisture has a much lower boiling point than new, dry brake fluid. Under the heat of heavy emergency or hard downhill braking the heat might cause the brake fluid to vaporize, your pedal goes to the floor, and your vehicle has no stopping power except the parking brake (which will soon overheat the lining). I've seen newspaper articles of two fatality wrecks locally where this has happened, and have one friend who had it happen and got stopped without a wreck, just soiled shorts. After the system cools the brake pedal feels normal...that's the clue.
Or, risk flushing the fluid and getting a speck of crud into a brake piston and have a sticky caliper which is easy to replace.