Brake Fluid Gunk.

Yesterday, I completed my second (solo) brake system flush. No bubbles,
solid pedal, and a sense of satisfaction.

I noticed the dark residue in the master cylinder reservoir (that still
remains). Three questions.

1) Where does this come from?

2) Short of pulling and cleaning the master cylinder, can this be
removed?

3) Can this buildup be prevented?

Thanks for your feedback.

 

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1) It may be some of the seals wearing, or it's just airborn DIRT, which
flows in and out when you use the brakes.
2) I remove the screen, then use a suction pump and a long bit of thin
tubing to suck as much out as possible before starting to do a bleed.
3) Keeping the brakes properly adjusted (if you have rear drums) and
keeping (compressible) air out of the brake lines might keep the
contamination WAY down, but just changing the fluid per the schedule in
the Owner's Manual should be enough.

'Curly'

 

Old fluid mixed with water, and oxidized by same.

Suck it out. Turkey baster will do fine.

Flush fluid once per year.

 

This sounds simple, but after sucking out the fluid, I wipe down the inside
of the brake and clutch reservoir with a high quality paper towel before
adding new fluid to my brake/clutch master cylinder. I get at least 90%
of the nasty looking stuff out that way.

 

yup, with a liberal dose of deteriorated rubber in there just for good
measure... tasty.

 

I just change my fluid once a year.

Last year my master cylinder finally wore out (248,000 miles). Wanna see
how much gunk I had when I dumped the fluid out?
http://www.tegger.com/hondafaq/mastercylinderreplace/replacement.html
See the pics about 2/3 of the way down.

 

During my flush, I kept the reservoir at least half-full. No bubbbles into
the lines.

1) When using the baster to remove the gunk, should I keep the reservoir
half-full? Or, OK to suction the reservoir dry?

2) Is it too late to go back and just remove the gunk without a full flush
this one time?

 

I assume you are talking about brakes. If there is visible gunk, and you
have a way to remove it, I would recommend removal. Then refill the
reservoir. I would have recommended doing this first, though.

Earle

 

You can suck it right dry. As long as you don't push the pedal before you
add more fluid, no air will get into the lines. Don't suck the fluid from
the port holes.

Nope. Remove anytime.