Hope M4 rear brake problem

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  • Hope M4 rear brake problem
  • brodie
    Member

    Sounds like you boiled it up, is it working now?

    Dales_rider
    Member

    Explain fad

    thegman67
    Member

    Now home but still not working. Leaver right back to the bars

    Premier Icon Onzadog
    Subscriber

    Were you dragging the brake? If so, it’s likely that you’ve boiled the fluid. A good bleed and a tweak of braking technique would sort that.

    If you weren’t dragging it, then there’s a very fine leak in the system. Clean and dry the bike. Bleed the brake, then tie the lever back over night. In the morning, go hunting for fluid leaks (a fine talc might help). Or it could be a failed seal in the master cylinder so it’s now not pushing fluid.

    thegman67
    Member

    Doing the uplift at Inners today,on my fifth run down my brake started to fad until I had no power in it at all. Checked for leaks on the calliper and handle but couldn’t see anything. Not opened up the reservoir yet but before I do has anybody any idea

    thegman67
    Member

    Thanks,will get onto it tomorrow

    Boiling M4s on UK descents would take some doing.

    I’ve had issues where the banjo bolt has come a little loose and fluid has slowly leaked out, almost unnoticeable.

    hazza123
    Member

    A good bleed should sort them out

    Premier Icon mikewsmith
    Subscriber

    How old is the fluid, what size rotors?

    Full bleed is worth doing anyway.

    thegman67
    Member

    The brakes are a year old with a 203 rotor. Just back from a week in the Alps

    allthepies
    Member

    Thegman67 wrote:

    The brakes are a year old with a 203 rotor. Just back from a week in the Alps

    could have been knocked around during transit, check all the lever-hose-caliper junctions. And…. was the bike stored upside down at all during storage/transit ? Fluid can leak out of the reservoir if stored upside down or vertically with bars at bottom.

    Premier Icon mikewsmith
    Subscriber

    check the fittings, the strap in my bike bag managed to pull the banjo round a little and cause a small leak. However you may just have given the fluid a good going over in the alps so just do a full flush through bleed, takes 20 mins.

    thegman67
    Member

    Thanks for the advice guys

    karen805
    Member

    I had a very similar thing happen to my M4’s in the Alps.. turns out that the bleed nipple was weeping (could see when I took the top cap off that it was missing some fluid). Replaced it, bled them though and they were fine.

    Dales_rider
    Member

    Facts
    Fluid cant leak out if upside down.
    Fade is when no mater how hard you pull the brakes don’t work, until you have had it you wont know what it is.
    If the levers pull back to the bars and don’t do anything you either have no fluid in the system or air in the fluid, or someones pinched your pads.

    Me I’d push the calliper off, the pads out, push the pots right back into the calliper [all 4] and dangle it from the bars.
    Get a largish 200 ml syringe and a piece of plastic hose that fits snuggly over the bleed nipple.
    Brake lever reservoir level.
    Take off top cap.
    open bleed nipple and pump all the fluid out. maybe catch it in something using tube mentioned above.
    Now fill the syringe and tube with new DOT 5.1 fluid, make sure you purge air out [like the doctors do with a syringe on the tele.
    Connect it to the bleed nipple and fill the system from the bottom till the reservoir is full, close the bleed nipple and don’t forget to roll your diaphragm in to the reservoir lid on and your brakes will be sorted.
    Check for leaks at some stage.

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