rear brake bleeding what am I missing? - BMW F800 Riders Forum & Registry



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  1. #1
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    I am trying to understand why I am having trouble bleeding rear brakes on 2014 f800 GT.

    I changed reservoir due to a crack- now can't get to hold pressure in the pedal. What am I missing? I bled at the wheel-is there a second bleeder bolt?

    I am missing something basic here.

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  3. #2
    Joepi5's Avatar
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    Sometimes there is an air bubble stuck in the master cilinder, had that once on a previous motorcycle. That would hold pressure but no bubbles came of the bleeder bolt. It's a pita to get it out though! I removed the brake line from the calliper and forced the master full of fluid with a syringe from the bottom.

    That did (at least for me) the trick, albeit on the front brakes.

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    The GS-911 gives you a way to cycle the ABS while bleeding. That may make a difference.

    If you don't have a GS-911, I'd try putting pressure on the brake lever and leave it overnight. Maybe hang a weight on the pedal. The pressure over a few hours will force the air through.

    Chris
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    IBA# 49894 True Rounder = 0-20's - Rounder -- to -- 100's+ Red Hot Rounder

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  7. #4
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    Agree with Daboo. Tried everything to get pressure back. Connected to a GS-911 and cycled the ABS system. Hey presto.....pressure back at the pedal. I think that somehow an air bubble gets into the ABS when any of the brake lines are disconected and cycling it (the ABS) cures the problem. Odd though that not everyone who disconnects a brake line has this problem. Probably depends whether you've been nice to the good fairy or not.

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  9. #5
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    Quote Originally Posted by Redned View Post
    AOdd though that not everyone who disconnects a brake line has this problem. Probably depends whether you've been nice to the good fairy or not.
    One trick I use when taking brake systems apart -is to seal the top of the master cylinder reservoir before I take anything apart. This prevents the flow of brake fluid while the system is apart, as there is no air allowed to enter the reservoir (a small amount of vacuum is created and it prevents the gravity flow of brake fluid). I either clean the top of the reservoir and use some tape......or remove the rubber accordion from the cap and put thin plastic wrap over the reservoir and install the cap. Another method you can use is to spread the brake pads apart a little bit - then pull the lever into the handlebar and put a rubber band around it to hold it in place (or hold the rear brake pedal down). By having the master cylinder piston activated it seals off the flow of brake fluid. By doing either method you stand a better chance of preventing air from getting into the upper portion of the system.

    I am not sure that prevents air from getting into the ABS system - but it does prevent the situation where the master cylinder goes dry and you need to bleed air out of everything.

    I also use a Mighty Vac hand vacuum pump kit to bleed brakes - it works very well on bikes, cars and trucks! It makes brake bleeding easy for one person as nobody needs to pump the brake lever (although I usually do that a couple of times at the end just to be sure I got all the air).
    https://www.amazon.com/MV8000-Automo...a-316724733774

  10. #6
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    Well I am a bit embarrassed but this might help someone else. It turns out that the replacement rear brake fluid reservoir has a tight, almost invisible clear cap . A riding buddy and I were perplexed until he noticed the cap-we could not get the brakes to bleed at all, of course. cap removed, issue resolved, brakes bled as expected.

    A silly error, but so it goes.

  11. #7
    BoxerBits's Avatar
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    Quote Originally Posted by jpmando View Post
    Well I am a bit embarrassed but this might help someone else. It turns out that the replacement rear brake fluid reservoir has a tight, almost invisible clear cap . A riding buddy and I were perplexed until he noticed the cap-we could not get the brakes to bleed at all, of course. cap removed, issue resolved, brakes bled as expected.

    A silly error, but so it goes.
    Glad you're sorted.

    Checking your work and having a basic understanding of hydraulic systems proves to be a solution. Hi Tec diagnostic equipment are wonderful things when used appropriately but a good basic knowledge is worth a whole lot more.

    Well done mate.

    As a side note, the old trick of holding the brake lever applied overnight, just allows any trapped air to naturally rise to the top of the system i.e. the reservoir. Nothing forces the air through. No need for any weights, just use a bungee strap to keep the brake lever applied.

    Ride safety.




    Sent from my moto g(8) power lite using Tapatalk

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  13. #8
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    Had anyone tried the moto scan app with obdlink LX to bleed the brakes?

  14. #9
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    Quote Originally Posted by BoxerBits View Post
    Glad you're sorted.

    As a side note, the old trick of holding the brake lever applied overnight, just allows any trapped air to naturally rise to the top of the system i.e. the reservoir. Nothing forces the air through. No need for any weights, just use a bungee strap to keep the brake lever applied.
    Sent from my moto g(8) power lite using Tapatalk
    Thats brilliant, thanks for sharing that one Nigel,,!!

  15. #10
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    I am usually able to get problem air out of brake lines by spreading the caliper. Then pump it back into contact with the rotor. Might have to do it a time or three. KTM front brakes are notorious for needing this after sitting a week. Only takes a few seconds. No muss, no fuss.
    2016 Yamaha FJR1300A; 2016 Beta 430RS; 2007 BMW F800S; 2009 Husaberg FE450; 2016 Subaru Outback; 2018 F150; 2013 Tesla Model S 85; 1983 Porsche 928S; 9 cats 

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