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Bleeding linked brakes for the complete idiot....

Discussion in 'Old's Cool' started by flemsmith, Sep 7, 2015.

  1. flemsmith

    flemsmith lurk

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    78 Guzzi T3.... Been bleeding on it for a few days now, read a lot of helpful stuff on line and in Guzziology. Even tried to follow a good bit of it, although not all (I really don't want to do a full bench bleed, nor have I removed calipers and hung them up in the air). So I thought I'd ask a few dummy questions and see if that gets me a little further along. I have the rear calipers acting like they're bled ok, I have speed bleeders on them, and getting flow with no bubbles when I crack them.
    Que's: 1. If I yank the bleed nipple, does that by itself introduce any air I should worry about?
    2. On the front nipple (std, not a speed bleeder), using the MityVac to apply a vacuum, if I crack it I get a lot of bubbles, but I think they're just coming the threads of the bleed nipple, how do I tell?
    3. I tried to bleed some intermediate connections, opened them and got some brake fluid out into a rag, how do I tell if there's still air there?
    4. Bleeding the master cyl...duh I cracked open the banjo connection, got some flow. same question as above.
    5. Assume a mityvac really isn't to use with a speed bleeder, ie won't generate enough pressure, right?
    #1
  2. chris a

    chris a Been here awhile

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    Yeah !Most Guzzi owners have been there....I found the best and quickest way after hours of frustration was to unbolt the calipers and raise then so that the air bubbles would rise.Never needed a speed bleeder or vacuume device but I'm a cheap old bastard.
    #2
  3. flemsmith

    flemsmith lurk

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    Thanks. OK, I'll try that...seems like I could just do that with the front left, thinking I have the rear bled pretty well. And do I want the brake lever tied down while I do it?
    #3
  4. flemsmith

    flemsmith lurk

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    OK, so now what? Assume I tie the brake lever down, wait until tomorrow and try to bleed it hanging up in the air? I was planning to replace the bleeder nipple thinking it might be leaking around the threads, so one of my original questions, can I just drop the caliper down to normal levels, release pressure on the brake lever, yank out the bleed screw, and replace it without worrying about a buncha brake fluid all over the place? Or extra air getting back in the system? thx for any advice. roy
    [​IMG]
    #4
  5. Wirespokes

    Wirespokes Beemerholics Anonymous

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    I haven't bled one of these systems, but have run into situations like this before. The rear disc on airheads behaves the same, and even the fronts have required removing the calipers and raising them in the air.

    If you're bleeding, you want the air to exit - raising the caliper higher than the rest of the system, the bleed nipple is the highest spot. Since air rises, it makes it easier for it to exit.

    I really doubt the bleeder is the problem. Of course some air could get by the threads, but not when it's tightened down. And when the pressure is higher on the other side forcing fluid out, air won't be coming in.

    It's a whole different thing roping back the brake lever. In that case, you want the air to come out the master cylinder, so ensure the lines aren't sagging forming places where air can't keep rising.
    #5
  6. flemsmith

    flemsmith lurk

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    Thanks, Terry. You working on your T3 yet?
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  7. flemsmith

    flemsmith lurk

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    So, I think I've got it! One thing I'm not happy with, the junctions at the proportioning valve were leaking...I used copper washers, and when I cracked them open I really wish I had put some of those rubber inserted seal washers there. I tightened them down a bit more and I'm waiting to see if they leak. If they dok I guess I get to do it over again after I replace those washers. So, what have I learned from my questions above? The Mity Vac doesn't really seem to have helped anything, I ended up using it to vacuum out the bleed lines when I was ready to lpull them off. Kinda minimized the spillage. The speed bleeders didn't really seem to make any difference either. I used them the same way I would have used a regular nipple, tubing fed into a container with some brake fluid at the bottom. I never did try to bleed the master cylinder except as part of all the bleeding I was doing. What I don't really know is whether I would have gotten the same result without opening the connections at the proportioning valve. YMMV roy
    #7
  8. Wirespokes

    Wirespokes Beemerholics Anonymous

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    I cleaned up the wheels and brake discs, next step is converting a bill of sale into a title. Not looking forward to jumping through hoops.
    #8
  9. chris a

    chris a Been here awhile

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    Flem , you shouldn't really need to open up the proportioning valve ....now it's done I'd get new copper washers rather than the rubber ones as those could be degraded by the fluid.Beware as there are two types of valve though....later Cali ones have true proportioning action whereas the earlier and by far most common type are simply a manifold.You have certainly got the earlier type.You need to pump the lever back and forth in order to load up the fluid and get the bubbles out .Hold the lever down after a good pump and then open up the bleed screw.Then close it repump etc.....I'd definatly have both calipers high up precisly because of the manifold trapping the air bubbles.You should be able to bleed the system pretty fast if you follow this unless there are leaks ,the master cylinder is bolloxed or you are not stoking the lever enough....
    #9
  10. flemsmith

    flemsmith lurk

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    Chris, Yeah, I'm beginning to think you are right that I did not need to open the intermediate connections if I hung both calipers up high enough to let air bubbles rise to the bleeders. It's just that there is a lot of advice/info out there about the best way to go about doing this, and I guess you have to learn what works best for you and end up ignoring some of the advice. As far as the copper seal washer, you're right, I had to replace one of them, still had a little seepage overnight after trying to tighten it down. I haven't received the "rubber" ones yet, so used another copper. Pretty messy. So now I'm bleeding again. BTW, I was using rubber as a generic term, not sure the exact material, but it is high pressure and oil and gas impervious (and reusable). I've used them before and never had a problem. Back to bleeding. I ended up yanking the rear caliper off and raising it so the bleeder was higher than the metering valve and the solid line. Got quite a few bubbles out, but I'm clearly not done yet, as the brake pedal is not as solid as it was before. So it's resting now with my 15 lb weight hanging off the pedal. I'll get there, it's just not something you can hurry. Thanks for inputs. roy
    #10
  11. bmwrench

    bmwrench Long timer

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    IIRC, and it's been a long time since I've worked on a Guzzi, the connections at the manifold need no seals at all. The flare on the lines is supposed to seal them.
    #11
  12. mach1mustang351

    mach1mustang351 Long timer

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    I struggled with my Spada for quite a while. What ended up working was I cracked the line at the rear master and bleed there. I then bled at the valve where the line comes across the bike. I then bled at the bleed in the valve. Next was the line to the rear caliper, reconnected and bled the rear caliper itself. I then disconnected at the hard line up front and pulled fluid from there. I bleed through the brake hose then reconnected the line to the caliper. This is where it got interesting.

    I couldn't get the caliper to bleed. I hung it up high and no luck. What I ended up doing was pumping the brake until the caliper was expanded all the way out. I then opened the bleeder and compressed the caliper pistons. This basically forces the air out of the caliper. I did this twice. I then bolted back to the bike and everything bleed out perfect from there.

    Maybe just an issue I was having, but maybe it will help.
    #12
  13. flemsmith

    flemsmith lurk

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    mach1....damn, that's a lot of hassle, and it sounds pretty messy. I'm not hoping I'll have to do all that, although I have done about half of it already.
    #13
  14. Scudman

    Scudman Been here awhile

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    After bleeding numerous systems I find that the last bit of trapped air is in the master cylinder. The only way to get rid of this air is by unbolting the master cylinder and while holding the cylinder horizontal gently squeeze the lever. You do not need to squeeze hard. The air bubble will come out the master cylinder hole located in the reservoir section. You need to do this a few times before all the air is evacuated. I never understood the zip tying the lever to the bar. I can only guess that the trapped air is forced around the seal. Due to the seal design the more pressure applied to the fluid the more the seal expands.
    #14
  15. Wirespokes

    Wirespokes Beemerholics Anonymous

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    I don't believe pressure has anything to do with it. Because the lever is back, the bleed-back port is open and the air then sees a way to escape in the dark when no one's looking.
    #15
  16. chris a

    chris a Been here awhile

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    I concurr Wirespokes!
    #16
  17. portablevcb

    portablevcb Long timer

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    My 'education' on brake systems was in auto shop back in the 60's so these 'modern' systems may not be the same :)

    The air bubbles are supposed to migrate to the master cylinder (the high point in the system). When you bleed the brakes it is done in a couple of sessions. The first bleed is done to get most of the air out of the system by pumping fluid and air through the bleed valve. That will get most of the bigger air bubbles. Then pressure is applied for a period of time, which is supposed to make the tiny air bubbles 'get together' to make bigger bubbles. Then the pressure is released and the system sits, allowing any remaing bubbles to migrate back up the line to the master cyl. Then you bleed it again. This time no bubbles should appear at the brake cyl, but, if you watch inside the master cyl you will see some bubbles as the piston is moved.

    The problem on the Guzzi with linked brakes is the splitter is at the high point. So, you either have to raise the calipers, the MC, or 'bleed' at the splitter. Whichever part you raise up let it sit like that for a while. Air bubbles in the small brake lines take a while to 'migrate'.

    charlie
    #17
  18. payner

    payner Been here awhile

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    :imaposer You used the word Modern in a Guzzi thread :rofl

    Sorry, had to do it.
    Chris... owner of a CX100 with mostly firm brakes and gallons of bubbly brake fluid kicking around.
    #18
  19. flemsmith

    flemsmith lurk

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    I did finally get a nice firm pedal, had both front and rear calipers up in the air for a coupla days. I prolly did some or most of what's been suggested, and hoping I don't have to do it again for some time now. Thanks for all inputs. roy
    #19
  20. chris a

    chris a Been here awhile

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    Yo !!!!!!
    #20