Hello all,

I have some strange experience with my brakes on '06 4Matic. Once in a while, I hear some kind of air leaking noise when I step on the brake pedal. It's not SBC buzzing noise I am familar with. Whenever I hear this noise, the feel of the brake is definitely different from normal status. This happened only few times. I think it was 5 times over 2 year period. I took my car to the dealership to have it checked, but couldn't repro the noise there.

Does anybody know if this is the symptom for brake failure or have similar problem?

Your expert opinion would be very much appreciated.

 

Does anybody have some detail on a backup hydraulic-only braking system? It seems to me what I have experienced was SBC failure. Of course, there is no proof for this since there is no error message at all.

Sir Konigstiger? What's your thought on this?

 

Can you describe more what happened? I cannot think of an SBC failure without any malfunction indication (never say never though).

 

I was backing my car in a stiff driveway. All of a sudden, I was hearing air leaking sound whenever I step on my brake pedal. The brake felt totally different from usual. I had to step on the pedal harder. It continued until I got to the destination and turned off the car. When I turned the car back on again, it was gone. As you could imagine, I wasn't able to repro this at the dealership.

When I read about the "backup hydraulic-only braking system", my gut tells me that what I have experience could be it. Maybe I am wrong