What causes brake fluid to turn brown / black?

tjl

Top Post Dawg
Joined
Mar 19, 2001
Location
California, USA
TDI
2001 Golf GLS
New brake fluid is clear. The two year old brake fluid that I just replaced is light brown. I've seen black brake fluid in cars where it has not been replaced for some time.

Does brake fluid turn brown or black when it absorbs moisture, or do bits of brake components that the fluid touches flake off and get in the brake fluid? Or some other reason?
 

GoFaster

Moderator at Large
Joined
Jun 16, 1999
Location
Brampton, Ontario, Canada
TDI
2006 Jetta TDI
Both. Moisture will make it darken. Wear in seals and other moving parts, and corrosion, results in suspended solids which makes it black with chunkies floating around in it. Replacing it on schedule, like you did, keeps the latter situation from happening!
 

whitedog

Veteran Member
Joined
Jul 12, 2004
Location
Bend, Oregon
TDI
2004 Jetta that I fill by myself
This is from my truck after I flushed it after... (nine years)



The light colored spot was floating on top of the fluid, but I was able to pull it out in one piece, although it pretty much fell apart and it did soak into the rag. When I got down to the bottom of the resivior, there was a small amount of very fine sparklies there. I wiped those out with a rag.

I think the white stuff was from water, but that's just a guess.
 
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