Changing brake fluid

[Oldred_V8S]

Just had the car MOT'd and was told that the brake fluid was 50% and would need changing at the next service. I have bled the brakes many times in the past and have no issue with doing this, my question is; how much fluid am I looking to pump out of the system at each wheel nipple before I am satisfied that what is in the pipes constitutes new fluid? i.e what is the capacity of the pipes between the reservoir and the nipple?

[phillpot]

Oldred_V8S said:

the brake fluid was 50%

No idea what that means ?

If fluid is "old 'n grotty" I'd expect to see a colour change as clean, new fluid comes through. Pipes are very small bore, quantity wise maybe I'd guess a mug full first rear,that will clear reservoir and long pipe to rear then much less from other three corners, litre in total should be plenty ?

[Griffinr]

Usually do mine at pad change, push the pistons back into the callipers, siphon all the old fluid out of the reservoir fill up with new then bleed through till clean fluid comes through. Probably only about half a mug full is bleed off in total.

I presume when they say the fluid is only 50% they have some sort of testing device which measures water content.

Rob

[jimed]

I changed the brake fluid on my S3C religiously every 2 years to avoid any problems and think that 1/2 litre was enough - certainly I didn't ever buy a litre can so must have been OK.
Jim

[Barkychoc]

If you go to a decent motor factors its really cheap - I bought 5 litres DOT4 for £11 odd plus vat.