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1986 FLHTC - Wrong Brake Fluid Installed

  • JustinCase
    JustinCase
    5 years ago
    I bought my cruiser about 1 1/2 yrs ago. At that time I asked many questions including when were the brakes last done and what DOT brake fluid had he used. 
    The PO said he was told by a mechanic to only DOT 4, which I thought was strange. 

    Fast forward to a month or so ago. Out on a run with a few guys, about an hour into it and the back brake was binding, not really locking up but was certainly dragging. When I pulled up the rear caliper was all but on fire with a shit load of smoke. I let it cool down for about a half hour whereby the caliper relaxed enough for me to ride it home just using the front brake. 
    Went to HD dealer today and bought some DOT 4 to bleed and top up after I put on a rear caliper kit. Dealer service manager was within ear shot and asked what model bike, he then said I shouldn't be using DOT 4 and to only use DOT 5. 

    So my Q is: Can I flush all the DOT 4 fluid out with a chemical of some sort and then start from scratch with DOT 5? Or should I replace the lines altogether? 
    I will of course redo the front brakes as well at the same time. 

    PS: I'm not made of money so costings here are an issue. 

    Input and constructive comments welcome. 

    Thanks.
  • perthhog
    perthhog
    5 years ago
    From previous experience  long time ago mine was  doing the exact same thing as yours   
    Even after flushing with fresh dot 5  than I rebuilt the caliper new seals  no grunge inside 
    It  mine still did it than I tried a new piston with it still the same  in the end I replaced 
    It with a  drag spec Oem copy  never a issue again   I put it down to a  housing issue 
    When warmed up  when mine got hot it  it dragged the bike right down to point 
    It locked up  and could hardy ride it off the rd. Than wait 20 min for to cool down so 
    Could get home 
  • JustinCase
    JustinCase
    5 years ago
    Quoting perthhog on 15 May 2019 10:08 AM

    From previous experience  long time ago mine was  doing the exact same thing as yours   

    Even after flushing with fresh dot 5  than I rebuilt the caliper new seals  no grunge inside 
    It  mine still did it than I tried a new piston with it still the same  in the end I replaced 
    It with a  drag spec Oem copy  never a issue again   I put it down to a  housing issue 
    When warmed up  when mine got hot it  it dragged the bike right down to point 
    It locked up  and could hardy ride it off the rd. Than wait 20 min for to cool down so 
    Could get home 

    Hey Perthdog, thanks for your comments. Did you simply flush the lines with DOT 5 and then bleed and all done? 
    I'm thinking that a reversing or neutralising chemical would or should be used best in order to totally remove the non compatible DOT 4. 

    I just read about some bloke who had a similar problem where he ended up replacing the rubber seal in the reservoirs, because they can basically just turn to shit and self dissolve with mixed brake fluids coming into contact with them. This of course highlights what would also happen to the seals. 
  • Bigfella
    Bigfella
    5 years ago
    Hope this helps.
    Basically its the glycol Vs silicone base. Check factory specs to see if your system can handle the glycol base internally, if so flush/fill with DOT 5.1 and your sorted.

    Brake fluid.png
  • DocGreen
    DocGreen
    5 years ago
    Quoting JustinCase on 15 May 2019 09:19 AM

    I bought my cruiser about 1 1/2 yrs ago. At that time I asked many questions including when were the brakes last done and what DOT brake fluid had he used. 

    The PO said he was told by a mechanic to only DOT 4, which I thought was strange. 

    Fast forward to a month or so ago. Out on a run with a few guys, about an hour into it and the back brake was binding, not really locking up but was certainly dragging. When I pulled up the rear caliper was all but on fire with a shit load of smoke. I let it cool down for about a half hour whereby the caliper relaxed enough for me to ride it home just using the front brake. 
    Went to HD dealer today and bought some DOT 4 to bleed and top up after I put on a rear caliper kit. Dealer service manager was within ear shot and asked what model bike, he then said I shouldn't be using DOT 4 and to only use DOT 5. 

    So my Q is: Can I flush all the DOT 4 fluid out with a chemical of some sort and then start from scratch with DOT 5? Or should I replace the lines altogether? 
    I will of course redo the front brakes as well at the same time. 

    PS: I'm not made of money so costings here are an issue. 

    Input and constructive comments welcome. 

    Thanks.

    Mate, it sounds like you're not really sure if you have dot 4 or dot 5 in the system already so why not suck/push some out and put it on a scrap painted piece. Dot 3,4,or 5.1 should bubble the paint after a while, dot5 shouldn't. Haven't had experience swapping fluid types but have read about horror stories of seals going to shit when different types flushed, so be careful. Your mc lids should state dot type recommended,  but this doesn't mean that is what is in there. 
    Good luck
    DocGreen
  • JustinCase
    JustinCase
    5 years ago
    Gday Doc, 
    I am sure it currently has DOT 4 in it as I've taken a look. DOT 5 usually has a purple appearance, whats in it looks like a yellowish colour (DOT 4). 
    The previous owner confirmed by text a short while after I bought it that it has DOT 4 in it. You're right, the reservoir lids confirm DOT 5 but old mate put DOT 4 in, wtf?

    After researching a bit I'm going to flush all the lines out and parts with denatured alcohol, just a fancy name for methylated spirits. Then wash everything in brake cleaner and maybe DOT 5 brake fluid including rinsing by blowing air through each line. I'm also going to replace the front and rear reservoir lid seals plus new seal kits per caliper. 

    We're talking brakes, don't want to chance shit going south at speed. Hence everything gets my full attention. 
    Thanks mate. 
  • perthhog
    perthhog
    5 years ago
    Quoting perthhog on 15 May 2019 10:08 AM

    From previous experience  long time ago mine was  doing the exact same thing as yours   

    Even after flushing with fresh dot 5  than I rebuilt the caliper new seals  no grunge inside 
    It  mine still did it than I tried a new piston with it still the same  in the end I replaced 
    It with a  drag spec Oem copy  never a issue again   I put it down to a  housing issue 
    When warmed up  when mine got hot it  it dragged the bike right down to point 
    It locked up  and could hardy ride it off the rd. Than wait 20 min for to cool down so 
    Could get home 

    Quoting JustinCase on 15 May 2019 10:23 AM

    Hey Perthdog, thanks for your comments. Did you simply flush the lines with DOT 5 and then bleed and all done? 

    I'm thinking that a reversing or neutralising chemical would or should be used best in order to totally remove the non compatible DOT 4. 

    I just read about some bloke who had a similar problem where he ended up replacing the rubber seal in the reservoirs, because they can basically just turn to shit and self dissolve with mixed brake fluids coming into contact with them. This of course highlights what would also happen to the seals. 

    Yes mate system was flushed about 3 times when I was chasing my problem 
    Same symptoms as you had 

    1st  flushed kit put in Caliper 
    2nd flushed new piston in caliper 
    3rd time  can’t remember if I flushed or topped up with new caliper 
    Master was only flushed rebuilt that about 5 years later 

    I did strip and rebuilt this bike frame up about 3mths after 
    the brake drama Put new wheels and chrome discs on  
    and that’s when I noticed after removing the Wheel 
    completely  that the  old disc had a about a 5 mm concave  
    from the Hub flange to the out side of the disc  from 
    so much over heating But showed no signs of warping 
    or shudder whilst I was using it  couldn’t Believe it 
    when I seen it  I didn’t  have a camera phone back than  lol 
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