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Thread: Rear brake fluid has turned dark

  1. #1

    Rear brake fluid has turned dark

    09 F650GS owner question here. My rear brake fluid has turned (coffee) dark with less than 1100 miles. Should it be changed, or is it just to be expected? Yes, I use my rear break a lot, especially in close quarters for example in a parking lot or to hold my bike in place when Im on a hill waiting for the traffic light to turn green and in San Francisco, thats about every other light. The bike was purchased new (with less than 14 miles) and both front and rear fluid colors were pale (beer) yellow. So is this dark brake fluid normal?

  2. #2
    Registered User dancogan's Avatar
    Join Date
    Aug 2004
    SE Michigan
    You can do a search for this over on, but I think you'll find that the consensus is that it's a sign of water in the brake fluid. Since the bike is under warranty I'd pay a visit to the dealer.

  3. #3
    Registered User
    Join Date
    Jun 2003
    Northern Front Range, CO
    Unless there is some kind of recall on the rear master cylinder unit (and i have yet to hear of one), i would be amazed if a dealer warrantied service for changing darkened brake fluid. i would expect that it would be called "result of normal usage" (just like need for an oil change), and you would be charged for the change.
    FWIW- factory service calls for brake fluid change after 1 year, and then every 2 years thereafter. my F8GS is approaching its 1 yr mark; front fluid looks crystal clear, just bled out they rear m/c as it had turned ugly color. took about 13 minutes using a Mighty-Vac. will get around to the front one later.
    Ride Safe, Ride Lots

  4. #4
    carving waves & turns kkaykk100's Avatar
    Join Date
    Feb 2009
    Rhode Island

    Dark rear brake fluid

    This happened to me just prior to my 600 mile check for my 09 F800ST. Dealer said according to BMW it was not an issue and would not be changed. I was waiting to have some other add ons for the bike which were not completed causing the bike to be in the shop for more than a week!... I really BITCHED, about everything and as an act of good faith they changed the rear brake fluid at no charge to me. That was more than a month ago and the rear fluid has not turned dark again. I really don't know if the dark brake fluid is an issue... but I fell better that the change was made and it is the color it should be. Just my .02.

  5. #5
    Grinning from ear to ear! bpken11's Avatar
    Join Date
    Jun 2009
    Camden NY

    Dark fluid seems to be normal

    If you go over to the forum at or Advrider you will find many posts on this subject. After much reading it seems that the problem is actually the pigment coming off the brake lines (only seems to happen on the rear) Some folks over at f800 have actually done some analysis on the fluid and determined that there was no water, and that the specific gravity, conductivity, etc. was the same for fresh fluid as it was for the dark red. The sum of all the post indicate that it is nothing to worry about and some riders have gone a year riding with it with no adverse effects.

    I guess I was one of the lucky ones, when I took my 800GS back to Max BMW in Albany NY, they just changed the red stuff out for me and put fresh in (no Charge) Everyone who has had this done has noted that the new brake fluid did not turn red ever again, even after months of riding. I can attest to that, that damn red spot is gone, and it has not returned!

    So it seems that you don't have to worry about it, go to the other forums to read the stuff yourself, and just get it changed at the next service if the red/brown makes you crazy!

    I better put in a disclaimer here, I'm not a BMW mechanic, nor do I present myself as someone who knows anything about the subject. I am just reporting on what I have read. If you think the red fluid will effect you personal safety, then you should change it immediately! (ok, I think my attorney will be happy with that)

    Hope that helps,
    Wow, this things a Blast!

  6. #6

    black fluid at MOA rally

    I had read much on the F800 riders Association site about the rear brake fluid turning dark and the many reasons why. So while I was at the rally in Johnson City, I went to the BMW NA display and checked out the bikes including "teaches" demo f800. All and I mean all of the bikes on display and for the demo rides and "Teaches" had black fluid showing in the small rear reservoirs. Apparently other than looking like it is sick, it has come to be accepted by the importer.


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