Why does my brake fluid look like this?

Discussion in 'Parallel Universe' started by aggiejet, Oct 4, 2019.

  1. aggiejet

    aggiejet Adventurer Supporter

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    315BF581-3B2B-4B10-B543-B0009D25F72C.jpeg 2E732E47-753F-4AA3-927D-52BB8C1A1606.jpeg

    I don’t know when this started looking like this. It wasn’t there in July riding in Colorado. I rode this past weekend pretty hard for 3 days (Adventure Palooza in Missouri) and noticed this “stuff” while cleaning my bike up yesterday.

    I sucked it out of the reservoir and put it in a clear container. Initially milky (i.e., the substance seems to mix with the brake fluid) this morning it has separated again and it looks like it did sitting in the fluid reservoir.

    Of note perhaps, after I removed the screw on reservoir cap, I noticed the rubber insert was misshapen (kind of folded up on itself)

    It’s time for fresh brake fluid anyway. Just curious what this is.
    #1
  2. jfauerba

    jfauerba Been here awhile

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    Maybe water? Brake fluid will pull water from the air.
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  3. JRWooden

    JRWooden never attribute to malice...

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    My guess would be the folded up rubber diaphragm allowed the brake fluid to absorb water from the air,
    or perhaps liquid water infiltrated......

    My suggestion would be Fix or replace the diaphragm flush system very very completely ... esp. if you have ABS ...

    The GS-911 has a special routine to help flush the ABS Controller......................
    #3
  4. shuswap1

    shuswap1 Long timer

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    That is exactly how both front and rear brake fluid looked in both of our F700GS bikes, less than 2 years old at the time, 2013 and 2014 models.
    Some operators attribute it to brake line material contamination. I sucked out fluid from the 4 reservoirs a couple of times, actually removed and cleaned the reservoirs and 2 years later the 'porridge' has not returned. I may do another flush this fall.

    BTW, I was very careful not to get any air into the system, even with the reservoir removed from the bikes and had zero issues with the ABS or entrained air afterwards.
    Just my 2 cents....
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  5. dpike

    dpike BeeKeeper Supporter

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    yeah, i had this sludge a while back too.

    [​IMG]

    i'm probably due to flush 'em again.
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  6. aggiejet

    aggiejet Adventurer Supporter

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    Albe has a YouTube video showing exactly same condition.

    I’m going to flush the brake fluid this weekend. Don’t know what a GS-911 is, guess I’ll google it. (just did. It’s a BMW BIKE OBD-II thingy)

    Manual says it takes DOT 4, not specifically BMW DOT4. Thoughts?
    #6
  7. aggiejet

    aggiejet Adventurer Supporter

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    HFS! That’s pretty knarly lookin’!

    I love your signature. Definitely suffer from that.
    #7
  8. aggiejet

    aggiejet Adventurer Supporter

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    D8E5717D-E2F7-49BB-9D1F-A95666B6A2FA.jpeg

    Here is a picture of the same fluid that I removed from the reservoir on my bike in the original post.

    I added 6-10 drops of water and stirred it up. 24 hours it looks like this.

    So it’s not water that caused that milky looking stuff.

    My guess is that perhaps there’s some sorta additive that turns milky with age, perhaps to signal a timely change.
    #8
  9. shuswap1

    shuswap1 Long timer

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    No, not water, best guess is it's probably some material from the interior of the hoses. The overall build quality of my old DRZ400 is far superior to this BMW. I do love the F7, however. I prefer not to use anything BMW sells, including brake fluid.
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  10. BygDaddee

    BygDaddee Long timer

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    its moisture absorption, nothing else, moisture has gotten in through your cap seal

    how long has it been since change, F8 are supposed to be changed first year and 2 years after

    build quality of the DRZ far superior, oh dream on
    #10
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  11. Tigershark48

    Tigershark48 My other BMW is a Roadster.

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    Brand loyalty sure can be blind. I’ve been reading some KTM forums lately and they can’t wait to trade in on the latest model, at the same time writing about all the everyday major failures they’re experiencing.
    #11
  12. vasuvius

    vasuvius wannabe something ... don't know what

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    I recently flushed my brakes and the rear looked exactly like that. The white sludge was sticky and I had to wipe it clean.
    I used Motul DOT 5.1 brake fluid and it seems to work fine. DOT 5.2 is silicone based and I don't think mixing silicone based with non-silicone based is recommended.
    #12
  13. Welshman

    Welshman B.U.F.F.

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    Brake fluid is HYGROSCOPIC, yours has managed to absorb water from the air, flush the system. :photog
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  14. aggiejet

    aggiejet Adventurer Supporter

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    Do you see this? Same fluid after I added some water and mixed it up. It got darker, but no milky sediment.

    D8E5717D-E2F7-49BB-9D1F-A95666B6A2FA.jpeg
    #14
  15. ROMAD

    ROMAD Been here awhile

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    Fwiw, my new to me 09 F8GS had the same milky sludge in the front MC too. Now I have front brake issues but I haven't found root cause yet so I can't attribute the sludge to my issues.

    When I examined the sludge in my hands it was kinda gritty and made me wonder if it was from brake line deterioration? Currently my bike is acting like a brake line is clogged but I haven't been able to replace the lines to see if that changes anything yet.
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  16. shuswap1

    shuswap1 Long timer

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    It's not likely moisture, both of our F700 bikes sat inside a fully insulated hangar when not being ridden the first 2 years and never-ever saw rain. And the heavy sludge formed in both bikes anyway....front brake as well as rear brake. I'm not sure what it actually is but like a previous poster said it was slightly gritty. I removed and cleaned the reservoirs and flushed both our systems, front and rear, and it hasn't returned in 3 years. I encountered zero issues with the ABS but was careful.

    It's utter nonsense to change brake fluid every year or even every 2 years, no matter what the 'book' says. For instance I finally changed out the original brake fluid in my 2003 DRZ last winter and it was absolutely FINE. That tatty old machine sees nothing but off road full throttle, max braking (ab)use.
    My wife's KTM 350 EXC-F calls for piston and engine valve replacement every 135 hrs and at 70 hrs if used for sporting purposes. Yet those engines are routinely running up to and beyond 600, 700 and even 900 hours in the field without any valve or piston issues.
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  17. BygDaddee

    BygDaddee Long timer

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    you don't measure moisture content of brake fluid do you
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  18. BygDaddee

    BygDaddee Long timer

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    show us the same mix again in about 8 weeks
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  19. aggiejet

    aggiejet Adventurer Supporter

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    I can’t, I poured it out.

    But to your point, after I suction removed the fluid from the front reservoir (including milky substance) I put it in the little glass and mixed it up. The next morning it was already separated out with the milky stuff in the bottom. I didn’t capture a picture of that.
    #19
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  20. BygDaddee

    BygDaddee Long timer

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