ABS or ASC Issue - Help Please?

    I have a problem with my ASC and ABS system. I posted this in Technical Issues but here may be better.

    My braking system works fine but is locking up when full force is applied. Thinking about this, it has been happening intermittently over the last couple of weeks and now occurs all the time.


    When I turn the ignition key on, the ASC warning lamp is on in the centre of the display and only when pulling away very slowly does the ABS light come on as well. I believe this could therefore be a common problem as the same systems share hydraulics. Has anyone experience on this please or possible pointers?


    When the car is first started there is a slight "gurgling" noise from the back of my 850 which could be the AHK rear axle hydraulics. I'm wondering if there could be air in the hydraulic system?


    When looking at the resovoir in the supply tank, the level of hydraulic fluid is some way below the gauze filter. Does anyone know the correct level as it is not clear in the owners manual?


    If the ABS lamp is lit a few moments after pulling away, I am assuming that the wheel speed sensors are OK and hoping that it is not the hydraulic pump assembly which is c.£1000 according to reports I have seen.


    Are there any fundamental tests that can be carried out to establish if it is a pump/fluid issue or electronics that may be the problem?


    I do like to drive with ASC off but seeing that orange light on all the time is off putting.


    Thanks for any help on this,


    Bob
    850CI

    Fundamental test: check with diagnostic equipment. ASC and ABS are readily diagnoseable.


    The gurgling noise you hear very likely is the petrol pump. Seems to be a common observation without any malfunction in store.


    The correct amount of pentosin can only be checked in a fully depressurized system. For the brake part of the hydraulics system you need to press the brake pedal around 20+ times (engine is OFF) until the pedal is really rock hard and monitor the hydraulics level. This releases the pressure of the "brake bomb".



    In a car without AHK the level ought to be about 1cm from the top of the reservoir well in the metal mesh.
    An AHK equipped car has another pressure reservoir which needs to be depressurized like so:



    Only after that you will see whether you have overfilled (quite popular - get some towels just in case) or are still below the recommended amount. Only use Pentosin 11S to refill. Do not mix with whatever salesbots may tell you. BMW sells this by the liter reasonably priced.


    Maybe it is worthwhile thinking about a change of Pentosin and the two filters (one under the radiator, one in the reservoir). This is not exactly cheap but has been known to cure the odd problem.


    I´d run a diagnosis first though - a malfunctioning ABS sensor may be the only thing that needs replacement.


    Cheers
    Reinhard

    For what its worth, when my ASC light became an annoyance (coming on whenever it felt like it) I was able to get rid of it by changing the filter in the Pentosin Reservoir and cleaning the filter in the ASC+T system. Was an easy, inexpensive fix.

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