F800s No brake pressure after bleeding - BMW F800 Riders Forum & Registry



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  1. #1
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    My first attempt at bleeding the brakes did not go so well. Tried using a hand vacuum pump and it was a piece of crap and introduced air into the system. Used the syringe method to reverse bleed my second attempt and it worked well.

    No bubbles present in either the rear or front mc. Bled the rear mc then two front calipers then the bleed screw just behind mc.

    Barely have any rear brake pedal and have maybe 1/2 pressure on front brake. When applying quick pressure to front brake can hear noise coming from what I believe to be abs system, near the air filter. Not sure if that's normal.

    Should I just take it to the shop at this point? Preparing for sale in spring.

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  3. #2
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    How does a vacuum pump introduce air to the system? It either sucks or it doesn't. It can't blow air back into the nipple.

    Sent from my SM-T813 using Tapatalk

  4. #3
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    Quote Originally Posted by bmwroadsterca View Post
    How does a vacuum pump introduce air to the system? It either sucks or it doesn't. It can't blow air back into the nipple.

    Sent from my SM-T813 using Tapatalk
    You're correct. I'm not sure but I feel like a mistake was made on my part. Brakes had no pressure. Either way any thoughts?

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  6. #4
    Runmyownlife's Avatar
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    It's straight forward but tedious.

    Normally, I'd say go buy speed bleeders but as you are selling the bike, go ask for help from a friend.

    1. Cap off the reservoir.
    2. Wrench on the bleeder valve. Do not open the valve.
    3. A helper (ideally) ready on the brake lever.
    4. Communicate to synchronise the opening and closing of the bleeder valve with pressure on the lever.
    5. Press the lever, open the valve, close the valve before the lever teaches the bottom of it's range of travel.
    6. Monitor the level of brake fluid - top up as necessary.
    7. Repeat many times.
    Concrete remains undefeated. 

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  8. #5
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    Got it. Does this need to be done because there is still air in the system even after not seeing any bubbles when reverse bleeding all bleeder valves?
    With the rear brake, there is basically no resistance at all. How would one be able to open and close if the brake lever is fully pressed in a 1/4 second?

  9. #6
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    The problem with pumping a brake lever to bleed the system is an air bubble will rise between pumps. In fact there is a vacuum when the lever extends.

    When flushing a system which starts devoid of air the pump method is sufficient.

    The ideal solution is to use a pressure flush such as offered by Motive Products. The difficulty is the reservoir cap needed to push fluid in from the top. Should be easy to find instructions online to build a pressure flusher using a hand pumped garden sprayer. But again, the difficulty is making a reservoir cap.

    The solution I “get away with” is a $34 Harbor Freight brake bleeder suction tool powered by air compressor. It uses a lot of air. Sucks from the bleeder but the fluid does not have to stop once it starts moving out. Put grease around the threads so all suction draws brake fluid and not air around the threads.
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  10. #7
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    Quote Originally Posted by N4HHE View Post
    The problem with pumping a brake lever to bleed the system is an air bubble will rise between pumps. In fact there is a vacuum when the lever extends.

    When flushing a system which starts devoid of air the pump method is sufficient.

    The ideal solution is to use a pressure flush such as offered by Motive Products. The difficulty is the reservoir cap needed to push fluid in from the top. Should be easy to find instructions online to build a pressure flusher using a hand pumped garden sprayer. But again, the difficulty is making a reservoir cap.

    The solution I “get away with” is a $34 Harbor Freight brake bleeder suction tool powered by air compressor. It uses a lot of air. Sucks from the bleeder but the fluid does not have to stop once it starts moving out. Put grease around the threads so all suction draws brake fluid and not air around the threads.
    Thanks for the response. My only concern is if I buy a compressor and this method of bleeding the brakes does not fix my problem. Could there be other reasons for my issue? I didn't see any air bubbles while reverse bleeding the brakes.

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    You don't have to press fast. Slow and smooth.

    If you have little to no resistance, there is either a leak (which you would see because of the brake fluid coming out) or there is air in the system.
    Last edited by Runmyownlife; 12-31-20 at 08:24 AM.
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  12. #9
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    Quote Originally Posted by Runmyownlife View Post
    You don't have too press fast. Slow and smooth.

    If you have little to no resistance, there is either a leak (which you would see because of the brake fluid coming out) or there is air in the system.
    Got it. So there is still possibility of air even after bleeding the brakes and not seeing any air bubbles?

  13. #10
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    Quote Originally Posted by sjb7w6 View Post
    Got it. So there is still possibility of air even after bleeding the brakes and not seeing any air bubbles?
    You won't see air bubbles if the air is staying in the system.

    I use a 26 gallon 150 PSI compressor, which stays busy when bleeding brakes. A $200+ item I doubt you want to purchase just to bleed your brakes.
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  14. #11
    notacop is offline The original Schwartz Wald Troll
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    http://kirbysbrakebleeders.ecrater.com/
    Bleeders make it easy, cost about $25 when I got some for my Vee Strom. Made the fluid change a 20 minute task. That hand held Mighty vac pump never worked well for me. POS.
    It's simple to get air in the system doing the job alone. Mistakes happen.
    With an ABS bike, having the 911 or similar and a lap top may be an aid in cycling the ABS pump. I'm not sure it made a tremendous difference in doing the bleed. But my friend Norm had the tools so we did it.
    I think the dealer wanted $100 to do the job but that was years ago.

  15. #12
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    sjb7w6 if you're still having problems or unsure if you've got the brake system free of air, Motion Pro has a simple check valve hydraulic brake bleed tool that I've found to work really well. Only costs about $20. Doing it yourself is really tough, even on a motorcycle and this check valve allows you to pump the master cylinder and add fluid while the check valve keeps air from being sucked back into the caliper/system. It works on any vehicle, so I've used it on my truck and old chevy also. Take a look, maybe could be helpful.

  16. #13
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    Quote Originally Posted by XR1000 View Post
    sjb7w6 if you're still having problems or unsure if you've got the brake system free of air, Motion Pro has a simple check valve hydraulic brake bleed tool that I've found to work really well. Only costs about $20. Doing it yourself is really tough, even on a motorcycle and this check valve allows you to pump the master cylinder and add fluid while the check valve keeps air from being sucked back into the caliper/system. It works on any vehicle, so I've used it on my truck and old chevy also. Take a look, maybe could be helpful.
    Just purchased these. I think this is my best bet. Thanks for the advice.

  17. #14
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    Got it. Hadn't considered the air was stuck.

  18. #15
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    Will probably go the 011 route if I can't take care of it myself in the next month.

  19. #16
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    Bought motion pro bleeders for front and rear. Worked like a charm for the rear brakes, now rock hard. The front brake 8mm one had a faulty check valve and leaked everywhere, exchanging now to try it again.

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  21. #17
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    Quote Originally Posted by sjb7w6 View Post
    Could there be other reasons for my issue? I didn't see any air bubbles while reverse bleeding the brakes.
    A possibility is that you have air in/within the master cylinder at/near the piston. This happened to me on a bleed for a newer GT. Air was introduced into the cylinder itself. No matter how much I bled the brake and pushed fluid out, I could not get any pressure to build up.

    The solution to this is rather simple, with the master cylinder cover off, just lightly feather the lever a few mm at a time repeatedly. This will dislodge any air and you'll see bubbles rise up in the reservoir.
    Claudio
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  22. #18
    Right Hand Drive's Avatar
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    +1 on Claudio's method. An alternative to that is to tie the lever back and leave overnight. You can use a bungi or a cable tie. This allows air to rise up into the master cylinder reservoir. In the morning you can then tickle the lever and you'll see the air bubbles rise. This method worked for me on several BMWs when I couldn't get a solid brake lever after bleeding. You don't need to leave the master cylinder reservoir cap off.
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  23. #19
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    If you can reverse bleed (force fluid from caliper back to lever) while wiggling the lever, you can usually get rid of those bubbles pretty quickly. Another tricky spot is bubbles behind the pistons in the calipers. Make sure to press the pistons all the way in before trying to bleed the caliper. It sometimes helps to use some wood shims to keep them from trying to come back out while bleeding. Just make sure to reset the pistons against the rotors for the final fluid level check.

  24. #20
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    Quote Originally Posted by Right Hand Drive View Post
    +1 on Claudio's method. An alternative to that is to tie the lever back and leave overnight. You can use a bungi or a cable tie. This allows air to rise up into the master cylinder reservoir. In the morning you can then tickle the lever and you'll see the air bubbles rise. This method worked for me on several BMWs when I couldn't get a solid brake lever after bleeding. You don't need to leave the master cylinder reservoir cap off.
    This
    Ajay

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  25. #21
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    Quote Originally Posted by Ajaay View Post
    This
    Ajaay

    Original poster looks to have sorted this issue back in December.

    Personally given that the bike is at least 10 years old, (F800S went out of production some time ago now), I'd be looking to do a full refurb of the hydraulic system.

    Ride safely.

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