Anyone ever experience this? I pulled off the cap on the reservoir and I noticed that if you shine a flashlight on the surface of the brake fluid, there are visible particles of what looks like dust floating on top of the brake fluid. Almost like when you spray sand on to water how it floats on top.

There appears to be no breach of the cap. I don't see any holes but I was told there's a vent hole on it somewhere. Could it have originated from the calipers? Maybe someone pushed dirty fluid back up without bleeding? I just want to make sure the fluid isn't being exposed to outside air and dirt at the reservoir while I'm driving. If it's coming from the calipers, fine, if it's coming from outside the reservoir then I'm worried since that means the brake fluid is exposed to air and water could be in it. To be safe I'm going to drain everything in the reservoir and replace with new fluid and probably check if dirt ends up back there after a month but if it's normal and it originates at the caliper this would be a moot point.

 

Never noticed it but didn't look for it in with a flashlight either. Do you change your brake fluid every 2 or 3 years? I find mine gradually gets dark which seems like a suspension of very fine black particles. Along with some yellowing which I never really tried to understand the chemical basis for that.

I found a tiny vent-hole in my 95 Integra, 98 Accord, 03 Accord. Never owned a 2009.

It might also come from the rubber piston-seals in the master cylinder. That way it doesn't have to travel far to get into the reservoir.

 

The '09 is certified used from a Honda dealership. According to CarFax the front brake pads were replaced around july of this year but other than that there is no proof the fluid was ever changed.

I'm suspecting maybe the dirt came from the caliper because the people changing the pads may not have bled when they compressed the pistons.

It could be MC seal material but it honestly looks like sand. Actually it looks like a grayish skin floating on top of the fluid as if it was skin growing on top of cold tomato soup. It's like a gray sheet of dusty looking skin. It's definitely not fine grained as in the fluid turning uniformly dark. The fluid color is overall a slightly dark gold, still clear and not anywhere near black. Then there's this clear gray skin floating on the top that's somewhat visible even without a flashlight.

Whatever, tomorrow everything in the reservoir is going out and being replaced with Honda Heavy Duty DOT3.

Under the reservoir cap there's this rubber pad that presumably seals to the funnel looking screen in the reservoir. Tomorrow I'll put some brake fluid around the rim of the funnel, dry off the rubber pad, then close the cap, remove the cap and check if the funnel and rubber are making good contact if I see fluid on the rubber pad. If it seals fine, I guess this dust "just came from somewhere".

 

You would be interested to see that in about a month, that new heavy duty dot 3 super duper fluid looks the very same as the stuff you are pulling out. Its from the condensation under the cap.