Question id love some help with here.

  They reccomend a brake fluid change every 2 years. I have a full service history with 1 exception: A service done in july 2022. Because of this i cannot see what was done then, or who did it. Just page 1 of 3 listing car details and that it was done. This service was not filled in the service book. 

 

  If it wasnt done then it has not been done since 2018. 

 

  So i checked it with a voltmeter. Negative lead on batterys negative pole, and positive dipped in the break fluid. 0.138v as i dipped it in, then it stabilized at 0.089v. 

 

  Not sure if this measures acidity, metal content from gradual wear of brake lines or moisture content. But it measures conductivity atleast. Ive heard from multiple sources online that over 0.3v is bad, means moisture content os above 3% and you should have fluid ASAP

 

  If fluid was changed 2022, which honesty seems more likely now its  still been more than 2 years. And it it hasnt been done since 2018 thats just worse. 

 

But is it good? Should i have it changed before my 1700km road trip in february?  Brakes work fine. 

 

Will check conductivity again when its not dark out and weather gets nicer. Making sure negative lead has propper contact. 

 

And have messaged the previous owner, waiting for a reply. 

No your fluid would not have been changed on a service unless you asked for it to be done this i have found out myself from prevoius services from dealerships they should do it but don't, to be honest unless you have done mega miles and done hard stops every day  or live in a rain forest 5 years is about the time to look at changing the fluid, can be done yourself or garage would do this but be prepared some places sting you and say it needs pads shoes discs etc or in one case they told my mate he needed a new set of calipers as the bleed screws were rusted in, but after a quick release spray they came out (replaced tem with stainless steel ones) much much cheaper than new calipers, did the fluid change for him as well new fluid new bleed screws all done for a couple of beers he was happy and I was to

6 hours ago, Ebbie said:

So i checked it with a voltmeter. Negative lead on batterys negative pole, and positive dipped in the break fluid. 0.138v as i dipped it in, then it stabilized at 0.089v. 

 

  Not sure if this measures acidity, metal content from gradual wear of brake lines or moisture content. But it measures conductivity atleast. Ive heard from multiple sources online that over 0.3v is bad, means moisture content os above 3% and you should have fluid ASAP

Never heard of this test before, but as long as you know how to interpret it to get water content it's as good as any other specific gravity test.

The brake fluid has never been changed in any of my family cars that I've serviced over the past 50 years plus. Most have exceeded 150k and 15 years, with normal use (no hard braking, rallying, etc.) when I got rid. Never had any issues. Maybe I've been lucky?

My fluid gets changed gradually when I replace flexi hoses or coroded brake lines. Never bothered changing it completely as had no problems with brakes. Did notice the clutch fluid was well past it when I changed clutch and slave. It was green/brown but the fluid to brake lines is still pretty clear. Bled clutch till fluid was nice and clean again.

Is the problem though your brakes will be fine, Until the water content causes the fluid to boil. That water becomes gas and you lose brake pressure, hence lose brakes.

So all is fine until heavy braking is required.

Fluid change is scheduled for next service (late summer). 

 

Thankyou all for your input ❤️

Edited 28 January, 20251 yr by Ebbie

I have never changed the brake fluid on any car I have owned. 100K miles and never touched.

19 hours ago, Jocko said:

I have never changed the brake fluid on any car I have owned. 100K miles and never touched.

 

It does improve your brakes noticeably if you change it when it's old.

A brake fluid change shouldnt be too bad to do as long as the bleed nipples arent seized. I have never bothered as all my cars are old and have had calipers or flexi replaced at some time and I tend to bleed them for a while afterwards to get new fluid through the system. I normally use penetrating oil for a day or two before hand and then use a little bit of heat on them and a spray of penetrating oil then some more heat to let it soak in. Havent snapped one so far. If I'm fitting new calipers or bleeding old ones I always use a smear of coppaslip grease on the bleed nipples before put them back for future removal.

Alasdair