break fluid change how often?

My personal priority in life is to move as much money from MY bank account, into someone elses.
 
I can confirm - after dragging an e34 525i out of a garage after 18 years hibernation - that brake fluid still does the job, even after such a period of time (very much to my surprise!!)

Not advising you leave it FAR from it, just noting its surprising that fluids you'd think were toast still - somehow - perform!
 
Daft question (and I probably should Google this), but if it's a sealed system how does moisture get in?
It’s not a completely sealed system.

Brakes that use DOT brake fluid are more prone to water or moisture ingress. DOT brake fluid is hygroscopic by nature which means it absorbs water from the environment via seams and microscopic pores in your hydraulic lines. This water content has an adverse effect on the performance of DOT brake fluid by reducing its boiling point.
 
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It doesn’t. Brembo and people have a say as part of their warranty agreements aswell as the application of physics.
Ah yes the physics of 'we aren't hydroscopic for 3 years but then we are and need to be changed'
 
It’s a curve of saturation to boiling point. Not a computer, it’s not binary…

It’s all fun then you tend to go into this “fun” utter BS mode. Which engineering degree have you got?
 
Ah yes the physics of 'we aren't hydroscopic for 3 years but then we are and need to be changed'

That's not what happens, it faces constant degradation from day 1, even when it's in storage. It's why if you only top up your reservoir or have a part open container after filling up you should dispose of it if you're not going to use it in the near future. The 2 - 3 years is generally the period whereby you're likely to be affected should you need some fairly consistent brake usage. Nobody likes pushing that pedal and finding you have just no bite at all because the fluid is boiling.
 
It’s a curve of saturation to boiling point. Not a computer, it’s not binary…

It’s all fun then you tend to go into this “fun” utter BS mode. Which engineering degree have you got?
Planned obsolescence 101. My other trick is filament light bulbs
 
It’s a curve of saturation to boiling point. Not a computer, it’s not binary…

It’s all fun then you tend to go into this “fun” utter BS mode. Which engineering degree have you got?
Okay so how does it decide it's cooked at precisely 3 years?
 
Okay so how does it decide it's cooked at precisely 3 years?

Because that's the typical point where it has absorbed enough water for the boiling point to drop. You could say the same about oil, it doesn't suddenly go bad after 1 year or 12k miles does it, it's a constant degradation. It can be tested easily.

Weird hill to die on, costs about £30-40 to be done every few years. Not like it's a massive scam. Having bled brakes before and seeing how black old fluid can come out, it's not something I'd want to avoid doing.
 
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This reminds me of people who don’t bother changing oil as it’s fine… until their timing chain snaps. Or those who use supermarket fuel which is fine until their diesel injectors fail…
 
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I've never done it on any vehicle or bike I've owned with the exception of one, where the dealer did it because I was trying to maintain service history. I'm not saying that's right. Just that... you ain't gonna die yo.

EDIT: Apart from mountain bikes, which I've had to do a fair few times.
What concrete evidence we have here
 
Yup.

Motorcycle is 20 years old, changed brake fluid once in the front system (separate brake systems) never on the rear.

Last car mitsubishi had it over 10 years, it was a few years old when I got that changed fluid once.

Mrs Fiesta us an 09 plate, changed once.

My Volvo is a 13 plate, I've never changed it, although I am going to this year.

All been fine.
Until it isn’t
 
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