6.5 year old brake fluid how can you tell when it needs changing.

I'm not sure, but I think since the prius isn't very heavy and uses regen for most of the braking, the fluid doesn't ever get warm and so the prius is easier on the fluid than most cars. the temperature change probably does affect the amout of moisture that gets in the fluid.
what I've noticed is that full size suvs the brake fluid would be nasty looking after 2 years, but smaller cars it would only be slightly discolored after 2 years. never tested the fluid, just flushed it at 2 years per MB maintenance schedule. only time I've had prius fluid flushed is when the '05 developed a kind of squeak while braking when it was cold out. tsb said to flush it.

 

The brake fluid is in a sealed system. You shouldn't need to touch it at all as long as you properly maintain the pads/disks and shoes/drums. As a machine design engineer who has worked in the automotive industry, the only cars I have ever seen that need the brake fluid changed are antique cars due to their age.

Bill the Engineer

 

Take the fluid samples from the bleed ports on the calipers and cylinders. The numbers and appearance may surprise you.

 

you've never worked on modern Benz's then because the brake fluid in the GL, ML and S classes all get nasty in 2 years of regular driving. these vehicles are all too heavy, and the brakes get a real workout stopping them. when the fluid turns brown or green, you really wouldn't want to leave it in the system. I've never actually tested it for moisture content, but when its badly discolored, something is going on.

 

With all the expensive brake system issues the Prius line has had, and recent change cycle to 3/36 for the Prius, Toyota's (and most cars/trucks mfgs) practice/recommendations, industry standard practice for DOT 3 and my personal experience...I'll stay with the "no such thing as lifetime fluids" school of preventative maintenance. Can't speak to your vehicles and experience but wish continued good fortune. My signature below is my practice, in the air and on the ground.

 

I personally think so.
At the extreme, my Dad's pickup truck went 20 years with no problems.

My only question regarding your story is:
In all that time and all those miles did you NOT have to do any brake work yet ??

I figure that I'll just wait until I need some brake work and then have it done then.
I'm guessing that will be at least 5 years and 50K miles.

 

Any time you've got the wheels being rotated is a good opportunity for brake fluid replacement, fwiw.

 

your dad's pickup probably didn't have abs or any complicated stuff in the brake system. when the fluid turns green, it means the brass valves in your abs pump are corroding. brown or black fluid may have corrosion going on too, plus the possibility of dirt or wear in the system. yes it is unscientific, but I would keep an eye on the fluid. if it becomes discolored, change it,

 

Probably a good rule of thumb.
I think I heard that it is designed to change color with the presence of excess moisture too.

 

I don't know if it was actually designed to change or whether that's just the way it is, but I've seen some really nasty looking brake fluid. and yet stupid cheap customers are like "I don't want to spend any money on that". can't fix stupid.

 

"But you don't understand. This is a magic vehicle with magic fluids and filters designed exclusively to last forever thereby saving the environment and the world from it itself."

 

They make brake fluid test strips for testing the fluid. I tested my 5 year old brake fluid a few months ago and it tested fine.

 

my dakota is 10 years old with 25,000 miles. how do you know when you have a brake problem caused by bad fluid?

 

My car has 91,000 miles now. At 100,000 miles I plan to check the brakes thoroughly, especially the calipers and pins. Even if all is good I will plan to take to the dealer and have the brake fluid replaced if nothing more than to be proactive.

 

I do my own maintenance work due to inadequate work by dealers and others. I have changed the ATF at 25 and 50k miles and plan to change it again at 100k.

You need Techstream to perform the brake fluid replacement which I do not have. I will have to trust the dealer on this one and check behind him thoroughly.