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Topic Review (Newest First)

  • 07-02-2012, 02:35 PM
    You have air in your master cylinder. You will not get that out easily with it on the car. It will most probably need to be bench bled and then re-installed with caps on the outlets to retain fluid and then pressure bleed the entire system.
  • 07-01-2012, 02:49 AM
    excellent thread

    So i left my system open for a week with brake calipers removed and I forgot to pour fluid back into reservoir

    When i came back after a week main reservoir was empty
    ( I know my bad , but i am doing it for the first time )

    Now i installed new rotors, pads, rebuild calipers and bled the system with compressor under 15 psi ( CNN method )
    All went smooth , no air bubbles but my pedal is soft and i have excessive brake pedal travel

    I believe that is because reservoir was empty and i probably got air into the system

    Tomorrow i will try to re-bleed my system +ABS with help of BMW software ( DIS )

    Wish me GL and thanks for any help ;)
  • 11-24-2010, 08:45 AM

    I've often thought about doing something like this

    But instead of having someone step on the brake I'd use my pressure bleeder and then connect a vacuum source to the bleeder nipple.
    Actually I could open the nipple and then step on the brake.
    Maybe I'll give this a try this winter.
  • 11-24-2010, 12:03 AM
    Craig in Canada

    Some bleeding info from DaveZ

    I know that DaveZ is still well respected around here as a "brake guy". I happened to be googling a number of topics and came across a couple of places where even DaveZ himself echos the same things I had read about power bleeding alone not getting the job done as well as the old-fashioned method.

    Assuming censorship doesn't botch the URLs:

    I think I'll still look into a power bleeder for convenience and to reduce the time taken by the operation, but some portion of the old way will still be in the procedure. I may also look at replacing the MC if lots of winter ABS action and a spring time bleed don't have things working like I would like. It's $300 and a huge PITA I'd like to avoid though.
  • 11-20-2010, 06:59 PM

    I was an ASE Certified Master mechanic...

    I saw alot of this stuff. Air in the system will cause a soft pedal all the time, not just on the first push. IMO you have a M/C going bad.Fritracer
    Cincinnati, OH
    2000 540ia Sport Package 9/99 Silver/ Black
  • 11-20-2010, 10:48 AM

    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.

    03 540i6
  • 11-20-2010, 09:40 AM

    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.

    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.

  • 11-20-2010, 08:15 AM

    It's called Boundary Layer Effect (m)
  • 11-20-2010, 02:16 AM


    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?

    Queens NY
    BMWCCA# 186796
    86 325es (wrecked by careless driver)
    87 325 (project for life)
    00 540is 6spd (daily driver)
  • 11-19-2010, 11:45 PM

    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.
  • 11-19-2010, 09:40 PM

    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.

  • 11-19-2010, 09:33 PM

    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?
  • 11-19-2010, 09:30 PM

    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.

  • 11-19-2010, 08:54 PM

    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.

    03 540i6
  • 11-19-2010, 08:50 PM

    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
  • 11-19-2010, 06:25 PM

    Forgot pic, got it at BAV Auto Show&Shine ~$70

  • 11-19-2010, 06:13 PM

    Dave, YES, works great, I have one

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  • 11-19-2010, 05:31 PM

    motiv bleeder


    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...

    03 540i6
  • 11-19-2010, 05:15 PM

    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.
  • 11-19-2010, 03:07 PM

    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
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