2007 Prius - To Flush or Not to Flush Brake Fluid

I over-maintain pretty much all systems on all of our vehicles, but I've only ever messed with brake fluid when master cylinder or line failure has made it the only option. None of our current family fleet ever gets even a drop of brake fluid added (let alone exchanged/bled) and none have had a brake related problem beyond pad/rotor replacement or slide pin clean/lube every spring. A single salt season/winter here can pretty much stop slide pins from sliding... I hate even opening the cap to push pistons back and try to pretend it's truly a sealed system. We don't have extreme heat but we do get pretty hot, and have four full seasons, including "cold spot in the nation" temps at least once every winter. It can't be an ideal setting for brake fluid but I've never seen a contaminated fluid related issue.

With a 4th Prius just added to an aging fleet including an '05 and '07 (and a crusty, but runs-like-new '05 Sienna that's a real candidate for brake line cancer), I'm pretty sure an actuator job or 2 will be in the cards at some point. I don't think I'll ever feel it could have been avoided with regular fluid changes, tho.

Be it right or wrong, it's how I roll. Full respect to everyone's opinion, too...

 

Brake fluids cumulate moisture and because of that boiling temperature gets lower -> possibility to lost brakes on heavy ABS braking.
Also that moisture does nothing good to brake cylinders. Brake fluid system is not high pressure so moisture gets there.
At lest, this is reason why here at Finland is said to change them.

Maybe it so that this issue is only on cold weather countries but gamble is high for not changing fluids ever O_O

 

This discussion sent me back over to Phoenix Systems's site, which I had not visited for a while, and it seems they have a nifty combo package of their tests that I don't think they offered the last time I looked:



I don't work for them, but I think I'll probably buy that kit. The last time I checked their site (however long ago that was), I think they only sold packs of 100 (too much money, I'd never use 'em all), or, like, onesy-twosies (mail order something every time I feel like testing something? not happening). A pack of 15 seems to pass the Goldilocks test for my purposes.

-Chap

 

Two trusted friends who are mechanics tell me that brake fluid becomes acidic after about 10 years. They recommend a total flush. Just had it done on my pickup for less than $100.

 

Having bought the Phoenix combo test strips some time ago, I had a nice day to use them last month, at 145,xxx miles. My results were similar to the ones hobbit got (shown in the last third of his page here). The strips measure dissolved copper, which would seem to be a way of taking any acidification into account.



Earlier reported test at 110,000 by hobbit: