workingdog
GOLD Star
My nearly brand new clutch isn't holding while the pedal is down. I opened the resevoir and instead of clear fluid there's this stuff. What's happened? Has water gotten in the resevoir? Has something else happened?
What's up with my hydraulic clutch fluid (1 Viewer)
- Thread starter workingdog
- Start date
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brian
SILVER Star
how old is:
the fluid
the master
the slave?
the fluid
the master
the slave?
workingdog
GOLD Star
- Thread starter
- #3
All brand new. Less than a 1,000 miles.
That master dose not look new . How about the hose?
I've replaced more than one auto-parts master or slave cylinder with "less than 1,000 miles". The rust on it indicates it's been some years...
workingdog
GOLD Star
- Thread starter
- #6
By why would the fluid turn this black color? What would cause that? Water?
Most brake fluid is hygroscopic. It will absorb moisture from the air which will cause internal components to rust.
The "black" is from seals/hoses dissolving in the brake fluid. It isn't anything for some of these parts suppliers to have product sitting a shelf somewhere for 5 or more years before they sell it as "new".
Most brake fluid is hygroscopic. It will absorb moisture from the air which will cause internal components to rust.
DOT3 and 4 are designed to hold water, but only a few percent. Brake fluid naturally turns darker as it absorbs water and ages. Darkness is not always an indication of rust in the system. The brake/clutch master cyl caps are vented, so over time, moisture WILL contaminate brake fluid.
You should use a turkey baster or MityVac and suck out all the black fluid from the clutch master reservoir, and then replace with fresh DOT3 brake fluid from a new bottle. At that point, open the bleeder screw on the clutch slave, and let gravity do the work - it will drip out and purge the nasty fluid from the line and slave. Keep an eye on the clutch master cylinder level, and add as needed (don't walk away and let the whole system bleed out on the ground). When clear fluid runs out, close the clutch slave bleeder screw, refill the clutch master, and you're done.
Then, do the same thing for the brakes.
DOT3 and 4 are designed to hold water, but only a few percent. Brake fluid naturally turns darker as it absorbs water and ages. Darkness is not always an indication of rust in the system. The brake/clutch master cyl caps are vented, so over time, moisture WILL contaminate brake fluid.
You should use a turkey baster or MityVac and suck out all the black fluid from the clutch master reservoir, and then replace with fresh DOT3 brake fluid from a new bottle. At that point, open the bleeder screw on the clutch slave, and let gravity do the work - it will drip out and purge the nasty fluid from the line and slave. Keep an eye on the clutch master cylinder level, and add as needed (don't walk away and let the whole system bleed out on the ground). When clear fluid runs out, close the clutch slave bleeder screw, refill the clutch master, and you're done.
Then, do the same thing for the brakes.
workingdog
GOLD Star
- Thread starter
- #10
Thanks. The cap for the clutch reservoir is right under the gap between the hood and the cowling and I'm wondering if all that water pouring in through that gap and onto the cap is causing more water to get inside.
Also, yes, the master does not look new. Perhaps they reused the old master when they installed the new line, slave and clutch ...
Also, yes, the master does not look new. Perhaps they reused the old master when they installed the new line, slave and clutch ...
It's pretty common and totally normal for the clutch fluid to darken/blacken, especially when components are replaced. The new master and slave cylinders are honed with a crosshatch pattern to aid in sealing, and low stiction. The crosshatching in the steel acts like a micro cheese grater on the rubber seals.
If you think about the distance the seals travel along that scored surface each time the clutch is cycled, and how often they get cycled back and forth while driving, it doesn't take long for the fluid to turn dark or black, contaminated with lots of microscopic particles of rubber. Once the rubber is suspended in the fluid, the back and forth motion of fluid through the system pushes it up into the master, where it can settle and stick to every available surface in the reservoir, making the fluid in the cup appear even darker.
Once everything is broken in, you should be able to flush it and have the darkening process take much longer, but it will still happen.
If it's not leaking anywhere, but it's not holding pressure, you may have air in the line. Also, check the condition of the rubber hose to make sure it's not expanding when you hold the clutch.
- Josh
If you think about the distance the seals travel along that scored surface each time the clutch is cycled, and how often they get cycled back and forth while driving, it doesn't take long for the fluid to turn dark or black, contaminated with lots of microscopic particles of rubber. Once the rubber is suspended in the fluid, the back and forth motion of fluid through the system pushes it up into the master, where it can settle and stick to every available surface in the reservoir, making the fluid in the cup appear even darker.
Once everything is broken in, you should be able to flush it and have the darkening process take much longer, but it will still happen.
If it's not leaking anywhere, but it's not holding pressure, you may have air in the line. Also, check the condition of the rubber hose to make sure it's not expanding when you hold the clutch.
- Josh
