Brake Fluid Question
Thread Starter
Team Owner
Joined: May 2001
Posts: 87,364
Likes: 1,592
From: Western NY
Brake Fluid Question
This is the question.....What causes brake fluid to turn brown?
This is the "back story".....I've owned my C-5 since 2001. Bought in new. I change the brake fluid every spring, when I put it back on the road. I'm in the process right now, of changing the oil, changing the brake fluid, and putting the "good" wheels and tires on it, for the upcoming season.
I last changed the brake fluid one year ago, and as I see it right now, it's brown in color. Never had this happen before. Does the ABS unit "store" fluid within itself, until the unit is actuated, such as in a panic stop?
The only time I ever actuated the ABS, in normal driving, was about 10-12 years ago, when a deer darted out in front of me, and I hit the brakes, HARD. I recently heard of people purposely looking to actuate the ABS to "exercise" it, by hitting the brakes on wet grass. I did that last summer, thinking it was a good idea.
Could doing this, somehow pushed old fluid through the lines, and back into the master cylinder? I'm stumped. and the look of that fluid has me concerned. And yes, the brakes worked well last summer.
This is the "back story".....I've owned my C-5 since 2001. Bought in new. I change the brake fluid every spring, when I put it back on the road. I'm in the process right now, of changing the oil, changing the brake fluid, and putting the "good" wheels and tires on it, for the upcoming season.
I last changed the brake fluid one year ago, and as I see it right now, it's brown in color. Never had this happen before. Does the ABS unit "store" fluid within itself, until the unit is actuated, such as in a panic stop?
The only time I ever actuated the ABS, in normal driving, was about 10-12 years ago, when a deer darted out in front of me, and I hit the brakes, HARD. I recently heard of people purposely looking to actuate the ABS to "exercise" it, by hitting the brakes on wet grass. I did that last summer, thinking it was a good idea.
Could doing this, somehow pushed old fluid through the lines, and back into the master cylinder? I'm stumped. and the look of that fluid has me concerned. And yes, the brakes worked well last summer.
Thread Starter
Team Owner
Joined: May 2001
Posts: 87,364
Likes: 1,592
From: Western NY
If this isn't the cause, I guess then I'd assume that brake fluid actually has a path that would allow it to "recirculate", in other words, on the chance that my actuation of the ABS, last summer, cleared the BPMV, and got the "old" fluid back to the master cylinder....yes?
Melting Slicks
Joined: Sep 2011
Posts: 2,258
Likes: 544
From: Appleton WI
Moisture and dirt can enter your fluid via the calipers. Any time you apply your brakes you extend the "pucks" that push against the back of the pads. When the pucks retract, you can introduce contaminants to the fluid. Even new seals will eventually allow some contamination into the fluid.
Thread Starter
Team Owner
Joined: May 2001
Posts: 87,364
Likes: 1,592
From: Western NY
After some more thought and consideration, I'm thinking that it just might be moisture "fouling" the fluid that's in the m/c reservoir. When I flushed fresh fluid through the lines, the initial fluid that came out, the fluid that was in the lines and calipers, was a little "tinted", as would be expected. Then a little "dirty" fluid came out, which was the last little bit that I couldn't suck out of the m/c, using a turkey baster. Then clean fluid flowed out.
It looks like it's time for a new m/c cap and gasket.....
It looks like it's time for a new m/c cap and gasket.....
Thread Starter
Team Owner
Joined: May 2001
Posts: 87,364
Likes: 1,592
From: Western NY
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Thread Starter
Team Owner
Joined: May 2001
Posts: 87,364
Likes: 1,592
From: Western NY
Most modern cars uses a bellows assembly in the cap of the brake fluid reservoir to allow for the movement of fluid from/to the reservoir during braking. The bellows would seal the system on the lower side to keep dirt and moisture out. But on the top side of the bellows it has to be exposed to the atmosphere (ie vented) in order for the bellows to work.
So if the bellows on the cap is torn or deteriorated it could allow moisture from the atmosphere inside the normally sealed chamber of the master cylinder.
Perhaps worth taking a careful look at your cap and the bellows......
So if the bellows on the cap is torn or deteriorated it could allow moisture from the atmosphere inside the normally sealed chamber of the master cylinder.
Perhaps worth taking a careful look at your cap and the bellows......
However, inspecting my OE bellows, it had a small crack in it, which must have been what was causing my issue. The new bellows doesn't have this opening.....
