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Brake calliper problem.

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  • beaglebasher
    beaglebasher
    3 days ago
    Some weird shit happening with the mixture. The purple stuff has turned pink and the green stuff has turned black. There is now 3 distinct layers.
    A thin black one on the top, then pink and then black. Still seems to be very liquid though. 
    I will give it another flush this morning and keep a sample of what comes out. 
    20251204_074130.jpg
  • speedzter
    speedzter
    3 days ago
    Add some pressure and heat , and it might explode 👍
  • beaglebasher
    beaglebasher
    3 days ago
    Yeah speedzter, I'm not convinced either. 
    That's what came out when I bled it this morning so there's still some of the dot 4 in there by the looks of things. If there is a cavity down the bottom of the calliper where the dot 4 can settle in I reckon I am fighting a losing battle. 
    I've just put the bike back together so I will take it for a run tomorrow and bleed it when I get back and have another look but I think I know what the story is. 

    20251204_180347_1.jpg
  • Hilly
    Hilly
    3 days ago
    That's the thing init, can't be sure you got it all, what a pitfa!
  • brucefxdl
    brucefxdl
    3 days ago
    Quoting beaglebasher on 03 Dec 2025 08:56 PM

    Some weird shit happening with the mixture. The purple stuff has turned pink and the green stuff has turned black. There is now 3 distinct layers.

    A thin black one on the top, then pink and then black. Still seems to be very liquid though. 
    I will give it another flush this morning and keep a sample of what comes out. 

    20251204_074130.jpg
    along time ago during my apprenticeship,before the arrival of brakeclean ,we used to wash brake components in metho.i dont know if a flush with metho or brakeclean would do the trick.the issue maybe the fluids have turn to gunk  and they may not "move ."
  • obisteve
    obisteve
    3 days ago
    Beags, I would recommend draining the current gloop completely,  and flushing with metho, then blowing through with compressed air if you have a water trap on your compressor.
    Metho will dissolve both the silicone and glycol fluids and any water in the system. Then refill with the right fluid, and flush through again until in runs through clean
    Expensive mistake, but not as bad as it could be yet.
    They changed the fluid used when introducing antilock brakes. Supposedly silicone fluid doesn't respond as well to the rapid pressure pulsations of ABS.

  • beaglebasher
    beaglebasher
    2 days ago
    Righty o, I will bite the bullet and buy a bottle of metho and blow it through the calliper. As Obisteve is suggesting,  if the dot4 is heavier than the dot5, if I take the bottom banjo fitting off the calliper any dot4 that is in there should come out.
    I will remove the bleed nipple completely and blow the fuck out of it in both directions.  
    The 50 50 mix has changed again since yesterday. The purple stuff has shrunk and changed colour to grey and the dot4 which started off being green and turned black is now turning purple.  
    There must have been a mad scientist in a laboratory at some stage who decided he should concoct a mixture that would fuck people up.
    20251205_055959.jpg
  • beaglebasher
    beaglebasher
    2 days ago
    Bought the metho and a big syringe and flushed the calliper from both ends about a dozen times, blowing it dry between flushes. 
    Hooked the line back up and bled it. 
    The purple dot5 that came out is absolutely clear so I am fairly confident that I got all the dot4 out.
    As it turned out, that little fuck up wasn't too expensive. All it costs was a bottle of dot5  ($31) $14 for the syringe (which will come in handy in the future) and $6.50 for the metho.  They wanted $17 for a bottle at the auto shop but I knew it would be cheaper at Woollies.
    Happy days !
  • obisteve
    obisteve
    2 days ago
    Glad that seems to have got it Beags.
  • obisteve
    obisteve
    2 days ago
    Beags, read your post again, I was recommending flushing the whole system, master cylinder and line with metho, not just the caliper. You never know where the gloop could be hiding.
  • Retroman
    Retroman
    2 days ago
    Already posted in another thread, but relevant here.
    When did Harley switch to dot 4 brake fluid?Harley switched from the silicone DOT 5 to the more performance oriented higher heat tolerant DOT 4. “DOT 4 won't compress,” important for ABS systems, that the tourers got firstThese models all use DOT 4: '06-later VRSC™, '07-later XL, '06-later Dyna and Softail, and '05-later Touring models

  • Retroman
    Retroman
    2 days ago
    PS I looked into changing my 2008 CVO Springer to "old" DOT5 silicone back when I got it in 2011

    That age came stock OEM with DOT 4 like all the rest of the range. And NO ABS to factor in.

    This was to try and protect the CVO Gunslinger paint scheme.

    Most all the info findable said "DO NOT DO IT".....

    Became a "too hard basket" job, so I just flushed thru' with DOT5.1 which is miscible (MIXABLE) with DOT4
  • beaglebasher
    beaglebasher
    yesterday
    Quoting obisteve on 05 Dec 2025 11:09 AM

    Beags, read your post again, I was recommending flushing the whole system, master cylinder and line with metho, not just the caliper. You never know where the gloop could be hiding.

    You're probably right,  I was assuming that after all the bleeding I gave it that any dot4 that was in the master cylinder would have got flushed through but as you say, not necessarily.  I will flush it with metho today.
  • beaglebasher
    beaglebasher
    yesterday
    Done. I caught a sample of what came out of the master cylinder and it was clear so I am confident that it was clean but I  flushed it with metho a couple of times anyway. I kept a sample of that too and there is nothing suspicious in there either. Bled it again and all is good. And there won't be any niggling doubts about it in the future. 
    One thing I will say about the dot5 is you don't have to worry if you spill any on the paintwork as retro said.
  • Hilly
    Hilly
    yesterday
    Good stuff Beages 👍
  • obisteve
    obisteve
    yesterday
    Yeah, good thing to do Beags, a bit of extra work to have peace of mind about your brakes is worth doing.
    Mind you, this is from a bloke who ran a 1950 Vanguard on 100% detergent in the brake system and only 3 wheels connected for about a year, an emergency repair that stretched out a bit.
  • beaglebasher
    beaglebasher
    yesterday
    Update on the back brake. 
    I took it for a run today and it's still getting fuckin hot. I'm thinking the disc is warped from ther previous abuse.  I spent an hour trying to find the dial indicator but didn't find it. 
    I checked the run out against the pads with feeler gauges and there is a 14 thou difference. so that might explain things. 
    I also noticed that the minimum thickness on the front disc says 0.180" .
    The stamp on the back disc says 0.205".
    If someone is taking their bike for a ride tomorrow it would be interesting if you touch the discs and let me know how hot they are. 
  • Stuart
    Stuart
    19 hours ago
    Quoting beaglebasher on 06 Dec 2025 09:43 AMedited: 06 Dec 2025 10:17 AM

    Update on the back brake. 

    I took it for a run today and it's still getting fuckin hot. I'm thinking the disc is warped from ther previous abuse.  I spent an hour trying to find the dial indicator but didn't find it. 
    I checked the run out against the pads with feeler gauges and there is a 14 thou difference. so that might explain things. 
    I also noticed that the minimum thickness on the front disc says 0.180" .
    The stamp on the back disc says 0.205".
    If someone is taking their bike for a ride tomorrow it would be interesting if you touch the discs and let me know how hot they are. 

    Mine get warm - you can touch them without burning your fingers, but they are pretty warm.

    Given the state of the pads you replaced earlier, I'm surprised the disc was still in a usable condition. I've had one of the pistons stuck, and I cooked the disc and pads. Destroyed the disc surface on the stuck side too.

    Are you certain all pistons are free? If you are pulling it apart again to replace the disc, I'd consider putting a kit through the caliper. Cheap and easy enough to do if you have a compressor handy.
  • beaglebasher
    beaglebasher
    16 hours ago
    Quoting beaglebasher on 06 Dec 2025 09:43 AMedited: 06 Dec 2025 10:17 AM

    Update on the back brake. 

    I took it for a run today and it's still getting fuckin hot. I'm thinking the disc is warped from ther previous abuse.  I spent an hour trying to find the dial indicator but didn't find it. 
    I checked the run out against the pads with feeler gauges and there is a 14 thou difference. so that might explain things. 
    I also noticed that the minimum thickness on the front disc says 0.180" .
    The stamp on the back disc says 0.205".
    If someone is taking their bike for a ride tomorrow it would be interesting if you touch the discs and let me know how hot they are. 

    Quoting Stuart on 06 Dec 2025 09:49 PMedited: 06 Dec 2025 09:50 PM

    Mine get warm - you can touch them without burning your fingers, but they are pretty warm.

    Given the state of the pads you replaced earlier, I'm surprised the disc was still in a usable condition. I've had one of the pistons stuck, and I cooked the disc and pads. Destroyed the disc surface on the stuck side too.

    Are you certain all pistons are free? If you are pulling it apart again to replace the disc, I'd consider putting a kit through the caliper. Cheap and easy enough to do if you have a compressor handy.

    Yeah mate, if I end up replacing the disc I will re-seal the calliper while I am at it.
    It's starting to look like that is what I will have to do. 
  • Hilly
    Hilly
    11 hours ago
    Beages are you able to prise the pads away from the disc easily? I mean do the pistons move smoothly? Sometimes the master cylinder can act up and hold pressure on the pistons, something sticking internally, the pistons can also jam a bit because they are dry under the rubbers, other thing that can happen is you get crud or rust in the brake pedal pivot and it just holds a little pressure on the hydraulic side, got to be something wrong.
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