Brake Reservior Dirty

[MaximaGuy]

While bleeding the brakes on SUV and the bottom of the master was real dirty - almost black, any ideas.
Filled it and bled brakes with new brake fluid. I regularly bleed but surprised how black the bottom was, any ideas.

 

[Warstud]

I think it's from the rubber on the MC cover and Brake lines.

 

[RichardS]

I flushed mine a week ago, and noticed some rather significant flakes of a dark green substance off of the reservoir side that came out when I suctioned the reservoir clear.

Maybe it's just the usual brake fluid gunk that builds up?

 

[Fastcompany]

Brake fluid should be done every 3 years if you have a sealed system for example you take your cap off and it has big rubber bellows. If your cap is vented to atmosphere like there is just a hole in the cap replace it every year and it will never get dirty or leave deposits. To clean an easy way is to suck it dry. Refill it and suck it dry again the next day. Brake fluid will quickly dissolve all that old stuff. I prefer if it's easy enough to pull the resivoir and clean it with soap and water and dry it well.also before a bleed I like to take a screw driver and push all the caliper pistons back in. This pushes most of the fluid up so you can suck it out. Less flushing to get clean fluid out the bleeders.

 

[E150GT]

Mine was so dirty I replaced it with the master cylinder. It needed it though.

 

[The Critic]

We service a newer Mazda 3 that has a similar issue. The vehicle received its first brake fluid flush at 3 years/50K. We found the reservoir to be stained, and the new fluid turned dark within a few days. We flushed the fluid again at the next service (as a courtesy) with a similar outcome. The brake system works fine and we know the fluid is serviceable, so no action was taken.

 

[mightymousetech]

That black/green stuff in the reservoir is algae. As the water content of the fluid goes up, it creates a perfect home for algae to grow.

That is a sign that it requires more frequent fluid changes. I recommend every two years minimum. Personally, I do it once a year

 

[Yah-Tah-Hey]

Neglected brake system. $$$ in your future.

 

[davison0976]

I flush brake fluid every 2 years on my two household vehicles. First change with Valvoline DOT 3 & 4 lasted me through the following two years without any issues. Fluid remained light in color and clear. Changed with same fluid 2 years later, and within 2 moths it turned Irish Breakfast tea dark in BOTH vehicles. I immediately flushed it with Lucas Synthetic DOT 3. Now 6 months later fluid remains very light in color and transparent. Go figure.

 

[LeakySeals]

I had that a month ago. Took a whole jug of supertech brake fluid, 4 drain and fills, to get rid of it. I'm assuming it was why the brakes seemed soft, squishy. Must have been in the master cyl below as well. All is good now. Still need to bleed brakes at some point. Or just keep basting, maybe the heat will move things around.

 

[MaximaGuy]

Using Valvoline Synthetic ATF for a very long time - maybe it is time to try out another brand.
Yes, the brakes were squishy until the old fluid was out of the master - the old brake fluid is less than 20K miles on it.