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Rear Brake Fluid BLACK

2

2andblue

COG Executive Director
Member
Fellows C14 enthusiasts my machine is a 2017 - 2 years from showroom floor and 26,000 miles. I performed first full brake vacuum flush - shocked to find rear brake fluid black. (not brown, Off color/shaded - black) No detectible debris, specks or chunks.

FWIW:
  1. Front lines flushed with basically what appeared to be totally clean, clear fluid.
  2. Have previously bled (not flushed) both front and rear calipers twice previously at maintenance and pad replacement.
 
Thanks.
But.
D*mn. :censored:
Means I'm going to have to look at mine this winter ... been putting it off year after year. Hopefully you're in the SE or some very humid climate vs. my lowhumidty area.
 
Sounds like excessive moisture is finding its way into the "sealed" system.
 
I can attest one can get some awful looking fluid in 2 years here in the PNW. Even those of us like Red Fox and I who live on the dry side. I change mine at the start of every season. Helps keep the muck out of other things like the clutch slave cylinder.

OP T&B, did you get both bleeders on the rear caliper?
 
I found I had to flush the rear a lot more than most bikes. I think it got better then worse again. Maybe it got it out of the ABS system too?
 
S Smith said:
Sounds like excessive moisture is finding its way into the "sealed" system.
Click to expand...
I wonder why is it the front is not experiencing the same level of moisture induced breakdown??? Is the ABS unit the weak link allowing moisture in? Front must have more than twice length of rubber hose and that fluid was near pristine.
I have usually thought of moisture intrusion as through the rubber lines...
 
2andblue said:
I wonder why is it the front is not experiencing the same level of moisture induced breakdown??? Is the ABS unit the weak link allowing moisture in? Front must have more than twice length of rubber hose and that fluid was near pristine.
I have usually thought of moisture intrusion as through the rubber lines...
Click to expand...

It's mostly steel tube.
 
The location of the rear brake reservoir will be exposed to much more heat than the front system also. On some of the Ducati's the rear master cylinder is located about 1" from a exhaust pipe with a thin heat shield to protect it. The fluid in those master cylinders turns very dark a lot faster than the fluid in the master up on the handlebars. You might have a piece of plastic meant to deflect heat out of place back there? If you want check the temps the rear MC is exposed to you could tape a digital meat thermometer next to it wit the read out at the dash area.
 
Heat - Didn’t think of that for the rear, however it is likely very true for the C14 as well.

Lesson here is flush your fluids on a regular basis, FSM suggests Brake and Clutch fluids every 2 years or 15K miles... ooops - went 26K.

Will do clutch next, expecting same black in clutch. To flush clutch line have to remove lower fairing, not a fan of removing plastic from ‘Blue’ yet, had her undressed now 3 times and each time is a new lesson.

Thank you each for the comments, hopefully this discussion leads to fresher brake fluids and for many less down the road problems from weathered fluids.
 
Brake fluid from clutch flush was barely broke down at all, however good amount of air. Amount of debris in clutch flush though was surprising - black bits, felt gritty.

Anyone else the same?

Post flush: Clutch May have small amount more throw, is about the same - no performance complaints.

BTW: In the Smokey Mtns now - the improved Braking / Brake Lever feel from full flush is pleasing.
 
2andblue said:
Heat - Didn’t think of that for the rear, however it is likely very true for the C14 as well.

Lesson here is flush your fluids on a regular basis, FSM suggests Brake and Clutch fluids every 2 years or 15K miles... ooops - went 26K.

Will do clutch next, expecting same black in clutch. To flush clutch line have to remove lower fairing, not a fan of removing plastic from ‘Blue’ yet, had her undressed now 3 times and each time is a new lesson.

Thank you each for the comments, hopefully this discussion leads to fresher brake fluids and for many less down the road problems from weathered fluids.
Click to expand...
I know this is an old post but wanted to add that I found the same problem with rear brake fluid that was dark brown. I just bought a '22 with 9300 miles. Rear brake fluid was very dark brown, almost black. Front brake fluid and clutch fluid were mostly clear. I was puzzling about what could cause this after only 18 months. There were no leaks, all the lines were intact without any noticeable wear, reserve tank and radiator caps were tight. The explanation of rear brake fluid being exposed to excessive heat makes sense. Going forward, I'll be changing the rear brake fluid more frequently than the recommended 2-year interval.
 
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