Is this an sbc problem

Discussion in 'Wheels, Tyres, Brakes & Suspension' started by flt.eng, Oct 23, 2011.

  1. flt.eng

    flt.eng Active Member

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    After using my w211 3 times, since a B service. Which included a brake fluid change. On applying the slightist touch to the brake pedal, I'm getting a very annoying sound. It's not easy to discribe. Other than, a squelchey release of fluid or air. Or something that needs oiling.
    The sound appears to come from the general area of the brake pedal. & lasts, less than a second & not very loud. This happens evey time the brake pedal is touched. Engine on or off. Braking appears normal. Any ideas. Before I take it back to the garage & they tell me it's some other problem. Not associated with the oil change. Which I feel it is.
     
  2. SPX

    SPX MB Club Veteran

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    Didn't you notice the SBC before the service?
     
  3. OP
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    flt.eng

    flt.eng Active Member

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    No. There was no problem before. This has only become apparent, in the last 30 mls. since the service. The service was done on the 3rd. Oct. Noice started Frid. 21st.
     
  4. OP
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    flt.eng

    flt.eng Active Member

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    My wife has just read this & she says that the noise has been apparent since the car came back from the garage. But thought it was normal. I have slight hearing problems. So did'nt notice it, at the start. It's obviously got louder.
     
  5. SPX

    SPX MB Club Veteran

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    Maybe the SBC wasn't working to its full potential before the service and now it is, you are noticing it?

    I know on my car that it buzzes at the strangest of times but that's just what they do.
     
  6. effbee584

    effbee584 Active Member

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    I have the same model and year car as Flt Eng, and on mine the SBC comes on with or without touching the brake pedal, ignition on of course. In fact I doubt there is any connection between touching brake pedal and SBC since it is basically a pressure vessel with a back up pump that keeps it topped up with pressure, actuated by a pressure drop in the pressure vessel, much like an aircraft hydraulic accumulator. The noise is quite distinctive and annoying, but definitely comes from the engine bay area, easily located with bonnet up. My SBC runs for 3/6 seconds at a continuous monotone at random times, sometimes audible when driving if the car is quiet. So I doubt that SBC is the culprit.
    Also, there are no hydraulic fluid pipes at or around the brake pedal in the car, although the master cylinder is just the other side of the bulkhead.
    Also doubt that a service would touch or even look at the brake pedal.
    Difficult to think there is air in the system.
    Causes?
    Maybe some trim was removed and not refitted correctly, now touching the pedal.
    Maybe there is a moving part that needs lubrication.
    Could be something in the seat construction that makes the noise when you shift weight to put foot on brake (a bit of lateral thinking).
    Action: try to really isolate noise, when and where and go back to service garage.
    Good luck.
     
  7. Dieselman

    Dieselman Banned

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    Possibly the brake fluid has some air in or the pedal has been greased and you can hear is squelching.
     
  8. OP
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    flt.eng

    flt.eng Active Member

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    I'm afraid this is'nt the same noise that the sbc normally makes.This squeeky/hiss, (just audible ) happens every time the pedal is pressed, over the first centimeter of travel. I'm checking with the garage tomorrow. So will report back.
     
  9. OP
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    flt.eng

    flt.eng Active Member

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    The garage was stumped with the squeak.did a test run,put it up on the ramp. Found a broken rear spring.( Which I already knew about) they had missed this on the B service. I'd already arranged to have these done by an indy. It came down off the ramp & low & behold. Squeak gone.
    Conclusion. If you get a squeak lift it up & down.
     
  10. effbee584

    effbee584 Active Member

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    Well Flt Eng, very relieved for you. Just shows how elusive some noises can be.

    Probably due to broken rear spring which has been dislodged or moved a bit. I would replace asap. One of my broken front ones collapsed causing need for tow truck, not nice to see!

    Wouldn't expect service to cover checking for broken springs though.
     
  11. OP
    OP
    flt.eng

    flt.eng Active Member

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    This could very well be. I have no idea how long I've been driving around,
    with 2 broken rear springs. there has been no indication of anything untoward. Until this. I only found the broken springs, When doing a carefull examination, myself. Prior to taking it to the main MB garage for its B service. Hoping MB, did'nt find the broken springs. (which they did'nt) As I had already arranged my indy to do the work. The trouble was. The squeaky pedal noise started imediately,after the service was done & before the new springs. This is being done next week.
     
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