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  1. #21
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    Re: just drive the damn thing for now...

    That's more or less what I'm doing, and have been doing for almost a week. After the second bleeding session the obvious "something's wrong here" feeling was gone but the micro-bubbles and two-press effect remain.

    Depending on how it drives over the next couple of weeks I'll see if I just leave it until spring and maybe invest in a power bleeder of some description before then.





  2. #22
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    2nd pump is always more firm in any car >

    You may not have a falling pedal right away. I had a bad mc in my m3 and had to douple tap the pedal to get it firm. The seals in the mc were starting to leak.

    Just something for you to consider.

  3. #23
    Eurodavid
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    Re: just drive the damn thing for now...

    Craig,

    Glad to hear it is slowly going away. Just wanted to comment on something. Since I have had this car, even at high speed autobahn stops and/or slow downs, I have never had to double pump the pedal. After the first push down (when starting the car), it is only very slightly noticeable that the 2nd, 3rd or 4th push is any more firm than the 1st push. I think if you notice it more than normal, it is just those once again stubborn bubbles. Also, did you try the left-front as last bleed option. When you mentioned that, I remembered the two times I have bled my brakes over the years, both times I started with the passenger rear, then the driver's rear, then the passenger front, and finally the driver's front. I am not sure if that is even the correct order in how BMW wants it done, was just going off of old memory in how I did on old American cars.

    Eurodavid

    P.S. Just last week had a bad scare that the brakes and car saved me from. Was coming up a 2km hill of sorts (7% grade), was in the open outer lane, going about 120kmph and still accelerating, when someone from the slower right lane doing about 35-40kmph decided to pull over without looking. They managed do this right when I was almost beside them, with no turn signal and/or warning. Only had time to hammer on the brake pedal once, brace myself for impact, but somehow, as my BMW tires started to slide (and the car slide dead straight, miraculously), the ABS kicked in, and I stopped just enough to avoid impact (along with the person finally yanking back over into the slow lane). I'm still not entirely sure how I didn't collide, and probably kill or hurt badly that guy in that little 2-dr Peugeot. I really believe in any other car (like my wife's ZTW or other American cars I have owned over the years), I'd have smacked hard with this person and hurt him bad.


  4. #24
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    Have you ever considered that the M/C cups

    are now worn? The symptons you describe are pointing to that. Even though you put a brick under the pedal, the pedal might have been pushed into virgin territory; this unused area usually is rougher than the rest of the cylinder do to the accummalation of sludge in the brake system. What happens is the sealing edge of the cup get very fine slits in it and does not create a good seal on the first push but the second rapid pedal push does due to the increase volume and pressure. The cup is not worn enough to bleed down with steady pressure.Fritracer
    Cincinnati, OH
    2000 540ia Sport Package 9/99 Silver/ Black
    img=168887[/IMG]

  5. #25
    Craig in Canada
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    Re: Have you ever considered that the M/C cups

    Well sure, I've thought of it. I'm fairly confident that "virgin territory" wasn't reached. In fact I'd be more concerned that an all out panic stop would more likely enter this territory than my bleeding setup.

    It's not a 100% certainty, of course. The thing is, what about these microbubbles in the LF/RR circuit? Even if the typical seal which fails from over-travel is what's toast it has fluid on both sides and it doesn't ingest air - or can it? I wish symptoms were clearer before considering embarking on a $300 and huge PITA project just to see if it fixes it. Bench bleeding plus installing without spilling everywhere, plus re-bleeding looks like a serious PITA.


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    The "micro bubbles" you are talking about

    could be cause by the fluid going thru the bleeders; they are not air tight at the threads and I have seen them draw air in thru the threads giving the impression of air in the system. I have also seen the cavitation caused by blockage of some type that cause air bubbles. I use a power bleeder that I bought 4 or 5 years ago; it was well worth the $100 or so that it cost; bleed all 4 wheels at same time without having to get someone to help; that alone is worth the money to not have to listen to the wife or kids whine "are we done yet?"!Fritracer
    Cincinnati, OH
    2000 540ia Sport Package 9/99 Silver/ Black
    img=168887[/IMG]

  7. #27
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    I'm not buying that because when you step on (m)

    the brake pedal the fluid gets pushed out to the calipers. Then you take your foot off the pedal the MC piston retract and the pressurized fluid is returned, granted a very small amount.
    Now if the rotation of the rotors were responsible for the pads being pushed back a small distance, tell me why after I do a brake job (all new components) before I put the wheel back on I step on the brake and then release it (to push the pads to the rotors) and I am able to turn the rotor freely without any problems.

    I say the 2nd press alway feels better because it's done before all of the fluid gets a chance to return to the MC, hence you don't have to move as much fluid or move the pads as far to get the same or better braking.
    That's my guess and I'm stickin with it.

    Sounds like removing the dash is a pretty big job, never had to do it on any car, hope I never do.

  8. #28
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    motiv bleeder

    Jim,

    Sorry to hijack the thread.. Do you recommend the Motiv brake bleeder? Time to do my front brakes, and may as well flush the fluid for the first time in three years. Hope I don't run into Craig's issues...

    dave
    03 540i6

  9. #29
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    Dave, YES, works great, I have one






    "Drive It Like You Stole It, A Sickness for Quickness"
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  10. #30
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    Forgot pic, got it at BAV Auto Show&Shine ~$70



  11. #31
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    Re: Update: 4th bleed

    Re step 3 - air in ABS unit.
    From what I can find out about the ABS system you need to activate the ABS system valves and pump during the bleeding process to shake loose any air bubbles trapped in the ABS hydraulic unit. (This is what the dealer bleeding equipment does) Activating the ABS by driving and applying the brakes to activate the ABS system doesn't necessarily get rid of the bubbles from the ABS unit, it just moves then around.
    You only need to do this if you get air into the system upstream of the ABS unit - Master cylinder, pipework etc.
    There are some BMW PDFs around which show the valve and pump layouts but they dont show which valves are operating and when during ABS activation.

    Hope this helps
    RonR

  12. #32
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    thanks jim,

    Did some research, looks like motiv makes the bavauto bleeder. I'll check motiv's local dealer, and order from bavauto if they don't have it in stock.

    dave
    03 540i6

  13. #33
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    Re: I'm not buying that because when you step on (m)

    The reason for the difference after a pad change is that the pads are retracted so far that one pump of the pedal can't move enough fluid to make up that distance. On upward pedal travel the MC draws from the reservoir if there's any "draw" and leaves the pads where they are. In the normal case, the pressure "returning" on pedal release is just whatever flex is in the system returning like a spring - the caliper isn't sucked back. All of the pedal movement is because of flex in various parts of the system - pure fluid isn't compressible so it's air, rubber brake lines, calipers twisting, whatever. I could see this "push only, no retract" behaviour when I followed advice from here and retracted the pads before my last bleed. Push the pedal - move closer - release - stays in the same place - push - moves closer.

    Next time you have your wheels off, look for clearance between the pad material and the rotor - you won't find any unless you have a runout issue.

    On the dash - other than a couple of hitches (which I still have to get the pics off the camera, mark them up, and write a thread about) it was a lot of stuff but really not that bad. Again, my personality and "skills" are such that I'd rather tackle that than removing my exhaust for the first time since the car was built even though the latter should be way "easier". Again, no pry bars, hammers, torches or 4' pipes added to breaker bars on the dash job :D I even said to my dad - "Wow, that was anti-climactic" when we loosened the whopping three screws to actually replace the motor.


  14. #34
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    On bleeders....questions

    So what's the deal here? As far as I know, MC caps aren't standardized. So if you're buying a power bleeder you need to be sure that you can outfit it with a cap that fits your MC? And it just so happens that BavAuto and folks like that sell them with BMW-compatible caps?

    Second, I have shop air. Do I want a system that uses shop air instead of a hand pump? I suppose you can use the pump one anywhere even if you don't have your air supply with you. On the other hand, isn't it bigger and requires pumping up all the time and keeping the pressure is a safe zone as opposed to dialing up 30psi or whatever on your regulator and just hooking it up? Thoughts?

  15. #35
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    Re: The micro bubbles you are talking about

    Well, I get everything all set up for the missus and then in a "normal" case of bleeding, she really only spends 5 minutes or so in the car including doing the clutch.

    On the other hand with the mega-ultra-saga-blog-bleed thing I've got going on she took a magazine out to the car...

    So, these micro-bubbles actually being caused by the bleeder - I'd like to know more about that. I'll use google, but if you have any place you know you've read that, I'd love to read it too. On past bleeds I was never looking as closely as this so they could have been there. I would normally only looking for "big" bubbles and I usually don't even have any of those. Generally I'm just waiting for the fluid to change colour.

    If I could rule the microbubbles out as a symptom of anything I'm just left with a little bit of remaining "two press" behaviour which could be a worn MC or nothing at all.


  16. #36
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    Typically shop air is loaded with humidity unless(

    you have an air dryer on your output line. Do you drain your compressor of air and water vapor when you are done using it every time?
    The BAV (Motive) one does come with a cap that fits our MC, fits my Volvos too. Once you pump it up it is good for all 4 calipers, 1 liter of fluid is really enough to flush the whole system.

    One my rant (ha) below about the pedal feeling better after the second pump I should have also mentioned that the first pump will heat up the pads a little bit (not a lot) and we all know that warm pads wotk better than cold pads.

    Microbubbles, someone mentioned this, air being drawn it. That is a real possibility. There is an effect (that I can't think of it's proper name) when a fluid flows thru a tube there is zero flow at the inside walls of the tube. All (or most) of the flow happens away from the walls. This leaves the inside edged of the tubing free to pull in air. This may be the small bubbles you are seeing.

  17. #37
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    EXACTLY!

    I hate bleeding brakes the old fashioned way. (pumping the pedal)
    An e30 and an old buick i had destroyed the Master cylinder seals cause they got pushed into "virgin territory". Most of the time that happens on an MC with high miles.

    Anybody know where to buy parts to rebuild a master cylinder at home?

    Andreas
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  18. #38
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    Yes | No

    It's called Boundary Layer Effect (m)


  19. #39
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    Re: just drive the damn thing for now...

    Craig, I haven't read your complete post here but when I had my fluid flushed by my Indie they had an awful time getting the air out of my system as well and finally they disconnected the clutch line to get the air out.
    FWIW........

    Jan/1998 528i, 5 spd manual, black on black non DSP.>300Kkms(180Kmiles) non-Sport, lowered with KONI FSD & Eibach springs in 2008, added "Bad Road package Adapters" to front only Dec 2009.
    My previous rides worth mentioning:1970 GTO "The Judge",1985 325e M3lite, Euro BMW +
    1998 323Ti, in Munich, Germany on the autobahn for 1 yr
    Now back in Halifax, Nova Scotia,via Ottawa Canada.


  20. #40
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    for the cap size

    motiv web site shows a full compatibility list of autos that their bleeder fits, by using different caps. The founder of the company was a bmw guy (since sold), so it will definitely work with our cars. I want it to work with my wife's toy LC also, so may buy from motiv vs bavauto.

    dave
    03 540i6

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