Yet another ABS thread

    Hi Chaps,


    As I have eluded to in other posts my car is close to making a come back. The current MoT fail list is broken coil spring (sledge hammer fix by putting Bilsteins all round) and the dreaded ABS/ASC light being on.


    I know there have been a number of similar threads and apologies for starting another one but the others have all confused me greatly. My car (1990 V12) has the ASC+T and I have had problems for years with intermittent ABS light coming on. The lights always come on then go off a moment or two after the engine starts, then come on again as you move off. Normally a engine restart fixes it, sometimes I need to restart several times but it always goes off eventually. The car has been sitting (dying :bawling:) for the last three years and has spent the last few months being slowly fixed by a BMW specialist. As part of the fixes he had to replace all of the brake lines so the braking system would have had a shock. I haven't seen it with my own eyes but he tells me the ABS light is on so I assume it's the same old problem.


    A few years ago I tried to read the codes using DIS. I could read almost all modules, but the ABS module couldn't be read. The mechanic has tried his code reader without success. I guess it could be a wheel sensor, but at £170 a go, trial and error doesn't seem like a good approach. I've read that even changing the pentosin can fix this? I don't understand how the ABS/ASC+T system works and I'd love to understand the relationship between the different components (pump, control unit, etc). Does anyone have any advice as to where to start with this?


    So close yet so far, please help!!

    Get your pencil and notebook out - here's your work for tonight, and don't forget to do the exam at the end:


    http://www.meeknet.co.uk/e38/E38_DSC_System.pdf


    Although it is for the later DSC - it covers ASC+T


    There are other ways to test the pre-charge pump (by shorting across the relay) to rule out a seized-up pump (which is the most likely fault)

    Thanks Timm.


    I flunked the exam at the end, but I think I've got a better idea of what's going on now, thanks.


    Is the pump the complicated/expensive looking thing in front of the near side front wheel? Can you give me a clue how to short across the relay?

    A new pump/hydraulic block is extremely expensive - but fortunately there are oodles of them around as they were also used on the 'lesser' models. And yes, it is in front of the nearside front wheel behind the lining:



    You can get the motor running by shorting out contacts 30 and 87 on relay K94:



    ...which is bottom left in the picture above

    Sorry... rainy day for a parade.... apologies.:dontknow:
    Entirely different system on the old dogs.


    The late M62 ABS/ASC unit is quite exposed to the wets and hence has found an untimely end in a few cases. One of the earliest to report the R&R procedure to my knowledge was Arnie who had to fix a 1999 model with extremely low mileage then.


    At first please establish whether you are confronted with an ABS or with an ASC problem or both - ASC warning will come up in the top center of the instrument cluster, also when pressing ASC button. ABS warning light is in the bottom right row of lamps and reads ABS.


    The ABS/ASC+T system in the old M70/S70 and IIRC most of the M60 unfortunately is nowhere near as "easy" to get to as in the later model. The ASC+T hydraulics (plunger valve) unit is tucked away underneath the brake booster/master cylinder unit.


    ABS circuit:
    If it were mine and no diags possible I´d first attempt to remove the ABS sensors, clean and check them (resistance) along with cleaning the sprockets on the wheel hubs. Sometimes the accumulated gunk is responsible for malfunctions as reported. Hardened over time plastic sheathing of the cables may have cut through a wire. Cost is Zero at that point apart from dirty labour and lots of swearing.


    Then I´d try and locate a Bosch service run by pensioners :D
    Bosch service stations (at least over here) seem to preserve knowledge of their olden but golden systems longer than BMW workshops do and they even might have different diags equipment to read out possible fault codes of the valve unit(s).


    Pentosin circuit:
    The +T unit in your case requires a special method to remove air bubbles from the circuit. Is decribed in the workshop manual - this will not cost anything at all and hands will stay clean (almost).
    If problem persists I´d go for the next "cheap" method which´d mean rejuvenating the Pentosin circuit and replace or at least thoroughly wash (w. brake cleaner) the filters. Please be advised that the one underneath the water cooler will be a bastard to open and possibly not open at all. This way malfunctions from overaged liquid can be remedied. Tom Carter reported success with this method many years ago.


    After that:
    You still have that ABS/ASC control unit in the passenger side footwell to check - I remember one report where water ingress led to the demise of such a E31 specific control unit. May be an explanation why you were unable to obtain diags via DIS.


    If replacing (one of) the valve units is the last resort be prepared that Xmas 2016 will be postponed... :roll:
    The units are both NLA (ASC and ABS) but can be found in cars of the period (E31, E32, E34). The ASC hydro unit as far as I know will only be present where the same (H31) braking setup was installed (that is at least E32 M70, according to parts catalogue also M60 but not sure about that).
    Removal of the ASC hydro unit is nothing for the faint of heart but to me at that point also not the thing to expect.


    Fingers crossed. - you´ll get there!
    Reinhard

    Zitat von NickF;133088


    My car (1990 V12) has the ASC+T


    Hi Nick,


    I am feeling your pain with this project. It is not fair that one man has such a journey, what with the accident a few years ago. Your perseverance and endurance is a credit to you.


    Just curious about the ASC+T as I am sure this was only available with manual transmission and I thought yours was auto therefore only ASC?


    Good luck with this latest issue and it is pleasing to note that you have the two masters chipping in with advice. Regrettably, I am only good for moral support:top:


    Cheers


    Graham

    Thanks Reinhard, looks like a good approach. I'm pretty sure both the ASC and ABS lights come on but I'll ask the mechanic to confirm. Sadly my hands are likely to remain clean as the car is 40 miles away and I have given up on trying to fix it myself, at least for now.


    Graham - it's not been the easiest car to own that's for sure, but like a lot of us on here I feel a very strong bond with the car and refuse to let it die. The mechanic tried to talk me out of fixing it but I wouldn't let him be defeatist. Although I've had to promise to arrange counselling after the pain and misery my car has put him through. Thanks a lot for your morale support, it's appreciated greatly. Not as much as Timm and Reinhard's expertise but almost ;)

    Hi all, quick update - I was with the mechanic last night and per Reinhard's advice he has removed all of the sensors and cleaned them but he said that all the ABS sensors were showing open circuit? He was testing them by disconnecting the sensor and measuring the resistance across the two contacts inside the plug. They were all the same so unless I'm monumentally unlucky he must be doing something wrong or open circuit is normal. Any clues? He seemed to think that they may use magnetic pulses instead of resistance change?

    The circuit diagram shows them as coils (and low resistance you would have thought):


    http://www.meeknet.co.uk/e31/e31_95.pdf#page=296


    RealOEM says 'Pulse Generator, ABS:


    http://www.realoem.com/bmw/enU…iagId=31_0155#34521180649

    I guess that explains why they are open circuit. I'll wait until the car is back together and hopefully the clean up has fixed it. If not I'll attack the pentosin circuit next. When I first got the car there was red stuff in the pentosin reservoir, presumably ATF. This apparently is bad so I drained the system as best I could and refilled with lovely green pentosin. I replaced the filters in the canister but the small one at the bottom of the system was a "bastard" (copyright: Reinhard) and I couldn't shift it. I had the whole front of the car off and had a big old spanner on it but it wouldn't give. It felt like I was going to damage something before it gave way so I gave up. Anyway, I'll make sure the fluid still looks healthy and the levels are right.

    Open circuit át least means: no wires broken which was what needed to be established somehow. Seen from there a potentially expensive point of failure has (probably) been ruled out.
    Without working diags it is guessing though. It just crossed my mind that there is a stomp test for the ASC+T system which will possibly give insight.


    German description of how to perform stomp test & error code listing.


    1) Apply brakes + hold
    2) Press ASC key and hold
    3) Ignition in position 2, keep ASC button pressed for at least 1 second. Release ASC button.
    4) The ASC lamp turns off. Readout of the error memory begins after 3 seconds.
    5) The number of flashing signals from the ASC lamp indicates the code for a stored error.
    6) If the ASC lamp does not flash: no error has been stored.
    7) 25 seconds after the readout started the process is finished. Error memory is cleared by pressing the ASC key within 3 seconds and holding it down for at least 1 second after 25 seconds have elapsed.


    -----
    If you already changed Pentosin in the past then I´d likely skimp out on that one depending on how long ago (miles) that was. You would like to make sure though that the ASC+T system is free of air bubbles proceeding as described in the workshop manual. The green CHF11S turns brownish over time and can be mistaken for ATF.
    Here some information regarding bleeding of the ASC+T circuit if not done already.


    Let us know what the stomp code shows - sorry for not pointing there earlier. Must be old age or something else that makes me stoopid :D
    Cheers
    Reinhard


    PS: GRAHAM: ASC+T was optional for the M70 Auto (S214). Around a quarter of all UK delivered RHD M70 were optioned with +T. It became a standard feature some time around March 1992.

    Open circuit does not sound right to me? Shogun's E32 ABS sensor testing procedure mentions a typical resistance of 1 kiloohm. That's of course from an older E32 but the same typical value can be seen in this E46 topic, so it's not unlikely the ABS sensor resistance of bimmers manufactured in between, like the E31, should be the same.


    Anyway, static resistance measurement is probably not a good way to diagnose ABS sensors but at least it should give an indication of broken wire / short circuit.

    Zitat von reinhard;133313


    PS: GRAHAM: ASC+T was optional for the M70 Auto (S214). Around a quarter of all UK delivered RHD M70 were optioned with +T. It became a standard feature some time around March 1992.


    Thank you for noting and clarifying my earlier query. Presumably it was initially felt there was less likelihood of spinning the wheels in the automatic which is why it was standard equipment only with the manual transmission. The extract below from the 1991 brochure confirms it as an option with the automatic.


    8er.org/forum/index.php?attachment/34301/

    Now that I have the car back I've got some time to look into the many problems that persist, and the ABS/ASC lights being on is up there.


    So I followed Reinhard's advice and did a stomp test. The ASC light flashed 15 times, this is reproducible so I think it's right. The german link didn't work, I don't think I have rights to access the german section. The internet claims 15 flashes is a pump problem - can someone confirm?


    I fired up my old DIS laptop and that still can't run anything to do with ABS or ASC.


    I think there are two things I can do in the short term. Bleed the pentosin circuit (i'll do that tomorrow) and change the lower filter for the pentosin circuit. I have tried this before and it was an absolute bastard, so much so that I gave up. It felt like I was going to do some damage. Is there a trick for getting that off?


    Assuming these two things don't work what part do I need to replace? The fault refers to a pump, is that the "hydro unit"? http://bmwfans.info/parts-cata…/brakes/hydro_unit_asc_t/

    I've been living with this, but since I'm putting a fair few miles on the car now (and loving it) I need to get this sorted.


    Looking through the ETM (RTFM) I've noticed that the stomp codes Reinhard posted in the German section are for ASC only, not +T. There are far more for +T.


    8er.org/forum/index.php?attachment/38638/


    15 flashes means ABS return pump defect. Sounds bad.


    The troubleshooting instructions require someone less moronic than me to understand them.


    8er.org/forum/index.php?attachment/38639/


    What is the "motor relay" and where is it?
    Where is the control unit?


    All help appreciated.


    BTW - I have flushed the pentosin and bled the system

    I've been doing a lot of research and I'm more confused than when I started. I've worked out that the control module is in the left door sill, so i guess I could crack that open and check for obvious problems like corroded contacts. There seem to be a lot of terms and I'm confused what is what.


    There is an "ABS Block" in front of the left wheel, there is the power steering pump and the ASC+T unit that sits below the brake master cylinder. All three of these things get referred to as "pumps". The term hydro unit gets used a lot, but seems to apply to the block as well the ASC+T unit. The error says the problem is the "abs return pump" but which unit is that? I'm so confused...


    I hope everyone hasn't abandoned this forum and I'm just talking to myself??

    This is nearly always the problem - and the 15 error code confirms it - if you are lucky you might be able to get it running again, but my guess is that you have had the problem so long that the pump motor is dead:


    http://www.meeknet.co.uk/e31/T…ing_ABS_Pump_Problems.htm


    The motor can be replaced (second hand), or the whole ABS/motor block can be replaced (second hand or very expensive new).


    P.S. I'm still here!

Jetzt mitmachen!

Sie haben noch kein Benutzerkonto auf unserer Seite? Registrieren Sie sich kostenlos und nehmen Sie an unserer Community teil!

Benutzerkonto erstellen Anmelden