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  1. #1
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    Problem with Shimano XT br-m785

    So I have problem with these brakes after bleeding them.
    Recently I got FS frame and rear brake hose was too short after old HT bike so I had to replace it. I did that, now it was time to put some new oil in system, I used LHM mineral oil which is used in Citroen cars (it is not DOT it is mineral oil) and it was suggested by friend who uses it often in all brakes that use mineral oil without any problems.
    After bleeding brake I noticed that lever is sluggish (if this is right word to describe it) lever travel is same as it is on front brake, stopping power is also ok (not perfect but ok), so only problem is that it returns slowly and it feels sticky...I tried rebleeding it but feeling stays the same. I was thinking of removing oil completely than refilling it completely, what do you guys think?
    What is the best way of removing oil from these brakes?

  2. #2
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    I've heard the LHM is slightly more viscous, which added to the fact that the newer Shimano brakes use the BH90 hose which has a smaller internal bore, can cause this problem. Drain whole system and re-fill with Shimano stuff would be my advice...

  3. #3
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    Hmmm, see and this is why I posted here I totally forgot about new power hose...I ordered shimano mineral oil, so I am waiting for it to come, meanwhile,
    what is the best way to drain whole system?

  4. #4
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    I've had really good luck with the little bottles of compressed air they use to clean computers. You can shove the little nozzle into the hose to blow out all the old fluid. I usually follow that up with some isopropyl alcohol and then blow all that out too.

  5. #5
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    Do you have the funnel that screws in to the lever?

    I was out of Shimano fluid and had to bleed my 785s the other night and it was so easy to purge the Shimano fluid and replace with Magura fluid by just inserting the funnel into the lever and pushing the Magura oil in from the caliper. Pushed Magura blood through until there was no more pink oil coming out of the lever, then dumped out the funnel/bucket and proceeded to bleed as normal.

    Thinking I might go back and replace with Shimano fluid though as I'm getting similar symptoms. My brakes are brand new so I wasnt sure how much was just the brakes and seals needing to break in.

    One thing is for sure, the pink Shimano fluid floated on top of the blue Magura blood. Might do the same with your LHM.

  6. #6
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    if you ask Shimano, using anything other than their "mineral oil" in their brakes will cause the universe to explode. maybe they are onto something.

  7. #7
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    @scottap2003

    ty for the tip, I'll probably remove brake hose and let gravity do its thing, after that it should be easy to replace LHM oil with Shimano's mineral by normal bleed procedure.

    @GTscoob

    Yes I have the funnel, as I said if I have time I'll emtpy the hose first, otherwise I'll just do normal bleeding procedure...it should do the trick and replace LHM oil completely...
    Also I'll take picture of mixture of LHM mineral oil and Shimano mineral oil.

    @mack_turtle

    Well, I think they started using this new BH90 hose, which is much narrower than previous versions of brake hose, just so that other cheaper more thick types of minera oil won't work

  8. #8
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    what is the best way to drain whole system
    Don't know if it's the best or easiest way, but if it were me, I'd...

    1. Attach yellow bleed funnel to lever reservoir, fill with Shimano oil.
    2. Take hose off at calliper by undoing banjo bolt
    3. Pump lever repeatedly while re-filling funnel with fresh Shimano oil to flush the old stuff out of reservoir, master cylinder, and hose.
    4. Take calliper apart and clean in IPA - see my thread if not sure how to do this Ever wondered how a hydraulic brake calliper works?, re-assemble and fill with Shimano oil.
    5. Do a normal bleed to get the last of the air out.

  9. #9
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    I know it is old topic but I had to write here so other people know that oil change solved my problem. New shimano brakes really only work well with original oil.
    Also worth mentioning is that I haven't drained brake first, I just did normal bleeding procedure and now it is perfection!

    Sent from my GT-I9300 using Tapatalk 4 Beta

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