Amazingly it seems that my brake fluid change is coming round again (well November). So I thought rather than just blindly doing a change with money being a bit tight I would test to see if it needs doing. Looking at https://amzn.eu/d/0gh1pjR8 Got a good write up in Auto Express a couple of years ago. Anyone test their fluid. I will admit the last time I changed the brake fluid in the Golf was 10 years ago (offer from VW that with air con service - £150), I think with a small top up about 6 years ago. Any one recommended a brake fluid bleed kit?
You can buy one direct from Aliexpress for about £2. https://www.aliexpress.com/item/1005007124947684.html I have one and find it quite useful. New fluid is 0% water. Sometimes older fluid creeps up above 1% water, but sometimes old and dark fluid is actually OK. The thing is that, especially if you have alloy calipers, you really need to crack the nipples every couple of years just to stop them seizing in place. I do check mine every year.
I don't know because for various reasons the brake fluid has been changed anyway. I can say that at 2 years the fluid tests at under 1% in one car. So this time I haven't changed the fluid.
The recommendation is to change out every 2yrs. TBH, given how inexpensive it is to have done at a Halfords/F1 Autocentre/KwikFit etc. I would get it replaced sharpish. It does take on water over time and become less effective and brakes will become spongey. Given it's a long time since you had it done, no doubt you'll have got used to the feeling over time. But where brakes are concerned, I'd be erring on the side of caution.
First let me say I'm not against changing the brake fluid every two years however I need to clarify a few points: Brakes only become spongy if air had entered the system - which it should not unless the system is opened up. Old brake fluid does not become spongy. The problem is water absorption. Water boils at a lower temperature than brake fluid. If there is water absorbed in the brake fluid and the brake fluid becomes really hot then the water will boil and become steam. This steam will just compress when you press the brake pedal and your brakes won't work until all the steam has compressed which will need more pedal travel. However to get the brake fluid to over 100C then the calipers will need to be over 100C which takes some serious braking. Water in the brake fluid also causes a secondary problem - internal corrosion of the braking system. If you test the brake fluid with a tester and it contains less than 1% water, or 0% water like new fluid, then changing the fluid makes no difference. Water absorption can only really happen if the cap is loose or left open, possibly it could be through the plastic of the reservoir. More air, or damp air in the reservoir would contribute, so how much water is absorbed will vary. I think BMW allow 3 or 4 years from manufacture to the first fluid change (rather than 2 years). However the brake nipples do seize in and it's worth cracking them open every couple of years, which is what happens when you bleed the brakes. If you just cracked them open momentarily then you could let air into the system.
So, got my new brake fluid tester this morning. BMW with 18 month old fluid 0% water detected. It will be interesting (well, sadly to me) to test at the 2 year mark. Golf with 12 year old fluid 2% water detected. I must say doesn't look the cleanest. I think I will give it a go and try and change the brake fluid myself (never done it so it will to good to learn something new) in the Golf in the next couple of weeks. I'll give the bleed nipples a wire brush and a drop of penetrating oil, as I will assume they will be a bit stiff.
Driving normally, you might not notice poor brake performance. But when say, descending a mountain pass, the brakes will heat up and at some point the moisture in the brake fluid will boil and become steam, resulting in having NO brakes at all. I would get the fluid changed ASAP after 10 years.
A good shout on a tester, hadn’t thought of this. The Boxster didn’t have any records of the fluid being changed, rather than do what I always do and throw money at it, I’ve ordered one of these.
So after testing the following: X reg Peugeot - never had brake fluid change - 1% - looked really clean Y reg Mazda van - never had brake fluid change - 3% - didn't look as dirty as the Golf Couple of very old Castrol bottles (very old labels) half empty - 1% I even found an old unopened one and tested - 0% I think I would have to conclude my brake fluid will be fine for at least 3 years. But I will test it obviously.
Your thread made me consider buying a tester, more so for the older Porsche than the BMW/EV. I’ve not got any history or paperwork as to a recent fluid change on the Porsche, rather than doing what I usually do and book it in, thought I’d test it out instead. Went for a cheaper Amazon version, £18 I think. Came today so popped outside and tested it. 1.4% is ok for now. Certainly fine until I change the front discs/pads later this year. A useful reference tool.
