Sources of water in brake fluid

Sources of water in brake fluid

Author
Discussion

stevieturbo

15,616 posts

216 months

Thursday 13th May
quotequote all
I would question the accuracy of the tool first.

test it on some other samples.

Although I've also seen cars decades old and the fluid never specifically changed...perhaps just fluid passed through when replacing other parts of the system and bleeding.

Although it is a service item at certain ages etc.....it's not routinely changed when it should be and to be fair, rarely is it ever an issue.

9xxNick

Original Poster:

767 posts

183 months

Thursday 13th May
quotequote all
I have tested it on other samples, as I mentioned earlier on. I get that it's rarely a problem, but if I'm paying for it to be done I expect it to be done.

bmwmike

3,777 posts

77 months

Thursday 13th May
quotequote all
Its not a completely sealed system though is it, I mean, the piston and piston seal may not be perfectly watertight or moisture sealing in all environmental conditions, evaporation and condensation due to temperature changes, atmosphere in the top of the resevoir, and a slight vaccum i guess, as the pads wear and the fluid drops over time pulling in new moisture. 4% is 40ml or thereabouts.

9xxNick

Original Poster:

767 posts

183 months

Thursday 13th May
quotequote all
Agreed, air has to get into the reservoir to replace the fluid that's taken into the brake circuit as the pads wear, but this is factored into the replacement time.

Anyway,I think we've done this one to death now, so thanks for the inputs.

LimSlip

738 posts

23 months

Friday 21st May
quotequote all
Evoluzione said:
If it bothers you use synthetic. When we order in BF now synthetic takes up 90% of the fluids available on the suppliers shelves, normal dot 4 is the remaining 10%. It's slowly being phased out.
Dot4 and Dot5.1 are "synthetic" fluids, do you mean the Dot5 silicone based fluid? It's not the panacea it was made out to be IMO.

NMNeil

2,277 posts

19 months

Friday 21st May
quotequote all
Ask the garage how much brake fluid they used.
On an average car, including the brake lines, the capacity of each rear brake caliper is about 0.2 liter and 0.3 liter for each front caliper. So about a liter in all just for the calipers. Then add the capacity of the ABS unit which takes a s**tload, and the master cylinder, means you need about 2 liters of fluid to to a proper flush.
To properly flush the ABS unit you also need a scan tool that can actuate the solenoids.
If it's a lot less, then they only drained and refilled the master cylinder.