steph280

On our 300 miles new E320, I noticed that after braking, I can occassionally hear a low humming noise for about 5 seconds. Originally I though the pads were grabbing, but it also happens after the car had come to complete stop. It almost sounds like some kind of pump running. I can't always reproduce it so I know what the dealer will say.

Any idea what this might be?

Thanks.

BudC

Your car has an electro-hydraulic braking system. The sound you hear is the sound of the pump. Your car does not use the pressure of the master cylinder to provide pressure to the calipers, it uses the pump.

Go here to see more.

http://www.whnet.com/4x4/sbc.html

ATS

Yeah I know what you mean, funny I don't hear it anymore.. When I first got the car I took it back in to service as it sounded "wrong". Don't worry, these are the best brakes you could have and the sound, like I said, I don't hear it anymore.

DWP

... but don't go looking for the "SBC stop" and "SBC hold" features. Those features aren't implemented in North American models.

I forget whether the humming/buzzing sound you may hear when you first open the door is the SBC cranking up, or something else altogether.

SAguirre

To make sure that that noise is the SBC system. Get in your car, but don't put the key in it or anything like that. Just push the brake pedal down at least 5 times and listen for the noise you will hear. If you hear it and it is the same noise you are talking about here, then it is the SBC.

There is a retrofit fix for this that Mercedes will do if you complain about the noise. Search under "Pulsation Damper" and you will find more about it.

I could not stand that noise and I had the retrofit done. Now I really have to listen hard to hear it.

I would of thought that MB would have made the fix a standard feature on the new models, but I guess not

Steve

BudC

The SBC wakeup signal occurs when you:

• Open a door
• Operate the central locking system
• Depress the brake pedal
• Turn the key to position 1
• Release the parking brake

wobbles

While E-Class models meant for the Singapore market DO get SBC Stop/SBC Hold, I also get a monopoly for a dealer, and the standard "Oh, that's the SBC pump firing up, there's nothing wrong with the hum" answer whenever I ask them about the dampener retro-fix.

Win some, lose some *shrug*

steph280

That makes perfect sense. Thanks for the explanations guys. Save me a trip to harass the SA.

I did notice there are some noises in the engine compartment as soon as I open the door. I was going to ask about that next but this thread answered them all!

Thanks again!

HELL ONA HARLEY

Yea, get used to all those funny little noises, buzzes, hummms and beeps. It all seems to be quite normal when the car is running or parked... As SAguirre mentioned, there is a "pulsation damper that can and will be installed by the dealer if you complain about the brake pump noise... My car also had the pump noise although it didn't really bother me, but decided to get the upgrade done anyway... I must say it made a big difference and I rarely hear it if at all now.... GL...

alewifebp

Yes, thanks to the forum I went to complain at my most recent service of excessive SBC noise. First my SA tried to tell me that it is normal, but I told him about the pulsation damper. Sure enough, when I looked at my work order, I see that the pulsation damper mod was done, and it is quiet. Very happy, as it was really starting to bug me.