shimano xt calipers leaking- Mtbr.com
Results 1 to 13 of 13
  1. #1
    mtbr member
    Reputation:
    Join Date
    Jan 2007
    Posts
    81

    shimano xt calipers leaking

    i was bleeding my shimano xt calipers yesterday using the Pentosin chf hydraulic fluid.

    everything was fine until i took it to the trail... i really had no braking power. after checking, i saw that my rotors were glazed with oil, and my brake pads were wet. further checking revealed that the hydraulic fluid was seeping out from the pistons... very badly.

    so i cleaned it all up and re-bled them.... and tried them again, but no luck, they still were leaking.

    what should i do now? the brakes were performing great before, just had a squishy feel to the levers which is why i bleeded them.

  2. #2
    mtbr member
    Reputation:
    Join Date
    Mar 2007
    Posts
    34
    What is Pentosin chf hydraulic fluid? Is it mineral? Could it be that it ate through the seals? There is a reason Shimano recommends one fluid...

    Was the bleed nipple completely shut?

    Did you bleed with a serynge or by gravity? Could the oil have spilled while you were bleeding and sat on the pistons until you rode?

  3. #3
    mtbr member
    Reputation:
    Join Date
    Jan 2007
    Posts
    81
    ya the bleed nipple was completely shut, and i bleeded as shimano tells me to. my first thought was that the oil spilled over... therefore i cleaned up the entire crap and rebled them and made sure i didnt spill anything. i cleaned up everything just after getting done with the bleed.

    but as soon as i started working the brake, i could see the hydrofluid comeing out in drops from the pistons...

    what could i do see where the problem lies?

    oh btw: the pentosin CHF is the synthetic hydraulic fluid thats used in my car's hydraulic system.

  4. #4
    Meh.
    Reputation: XSL_WiLL's Avatar
    Join Date
    Nov 2004
    Posts
    17,508
    No parts to rebuild. Time to send it back to Shimano and hope for a warranty.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Jan 2007
    Posts
    81
    i guess thats what ill do... but i just wonder what the heck went wrong with it? it was working flawlessly before i bled them.... the only change i made during this bled was using the pentosin fluid instead of the stock shimano hydraulic oil, but that shouldnt make a difference.

    i dont get how the pistons can crap out like that...

  6. #6
    Meh.
    Reputation: XSL_WiLL's Avatar
    Join Date
    Nov 2004
    Posts
    17,508
    BTW... you'll want to flush out the Pentosin before you send it back...

    Could just be your seals were on their last leg?

  7. #7
    mtbr member
    Reputation:
    Join Date
    Jan 2007
    Posts
    81
    thanks for the heads up on flushing the pentosin out.... that would have gotten me screwed

    i purchased them new two months ago.. the QC of shimano might be screwing up i guess

  8. #8
    Saving lives with knives.
    Reputation: frank daleview's Avatar
    Join Date
    Jan 2004
    Posts
    944
    Not a QC error. Synthetic automotive grade fluid is corrosive stuff. The shimano systems are designed for mineral oil use only, not synthetic automotive fluid. The synthetic fluid probably degraded your seals which is why they are leaking. And yes, if you want any chance of a warranty, definitely flush out the Pentosin with mineral oil.
    Formerly known as iceaxe

  9. #9
    ...idios...
    Reputation: SteveUK's Avatar
    Join Date
    Apr 2006
    Posts
    5,662
    "Not a QC error. Synthetic automotive grade fluid is corrosive stuff. The shimano systems are designed for mineral oil use only, not synthetic automotive fluid. The synthetic fluid probably degraded your seals which is why they are leaking. And yes, if you want any chance of a warranty, definitely flush out the Pentosin with mineral oil."

    Pentosin is mineral oil. It's hydraulic (power-steering, suspension, etc.) not brake (DOT) fluid. The OP is not the only person to use it in Shimano brakes, others have done so without issue.

    What use is a philosopher who doesn't hurt anybody's feelings? -
    Diogenes


  10. #10
    SLX
    SLX is offline
    mtbr member
    Reputation:
    Join Date
    Aug 2005
    Posts
    657
    Automotive oil is usually a DOT fluid, which is very different than mineral oil. The seals probably swelled up and thus the leaking. Some bike disks like hayes use DOT like Hayes it just depends on the manufacturer.

    Edit.. steve says that it is mineral oil so it may just be bad seals.
    Leave no bolt untuned!

  11. #11
    -> SickLines.com <-
    Reputation: mtb_biker's Avatar
    Join Date
    Jan 2004
    Posts
    3,196
    All signs point to the foreign fluid you used as the cause.

    If both brakes were fine before the bleed, then immediately after they both failed on the trail to me that's a sign of failure with the fluid you used. It just would be severely unlikely that this would happen on its own to both calipers.

    If one of the brakes stopped working, then i could maybe see that as a reason but the fact that both failed immediately after using the fluid says something is amiss.

    There's a few scenarios that could've caused the seals to mess up, including some chemical reaction between the shimano fluid (if not bled out fully perhaps) etc.

  12. #12
    Saving lives with knives.
    Reputation: frank daleview's Avatar
    Join Date
    Jan 2004
    Posts
    944
    Sorry, my mistake, I had not heard of Pentosin before. He mentioned it was synthetic hydraulic fluid so I assumed it was a brand of DOT fluid. Still, it just seems a bit odd that they began to leak right after he changed the oil. I would still flush them out, send them back and hope for a warranty. I have two sets of shimano brakes, one of them is a set of the XT quads; both are still going strong.
    Formerly known as iceaxe

  13. #13
    mtbr member
    Reputation:
    Join Date
    Jan 2007
    Posts
    81
    ya the Pentosin is a mineral oil based fluid (i use in my power steering), and i was told that it works flawlessly (if not better) than the stock shimano fluid.

    indeed all the actions do point out that screwing around with the oil messed up the brakes, but oh well.

    i cleaned out the system completely, and i think im gonna send it in for warranty repairs. I did clean out the brakes of the shimano fluid before putting pentosin in.

    edit- yep, the surprising thing is that it happened on both the brakes.
    Last edited by _ALX_; 10-07-2007 at 12:35 PM.

Members who have read this thread: 2

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2019 VerticalScope Inc. All rights reserved.