Just picked up my '05 E320 4matic on Sat. and have heard a strange noise. When driving or backing up, it sounds like one of those mini compressors you use to fill your tires. It last for about 5 seconds each time (spuratic) and I can feel the vibration through the brake pedal. Very annoying! Any ideas? Will talk to the dealer tomorrow, but thought I'd post it here first. Thanks!

 

Sounds like the SBC brake pump that runs to keep pressure built up for the braking system. It's normal for it to run but it shouldn't be felt in the brake pedal nor sound very loud. Talk to the dealer about this fix...

Bulletin P-B-42.46/27A – Install pulsation damper for SBC Noisy brake pump

 

BudC, thanks!

 

Yeah I remember when I first heard that sound, I hated it.. Now, I don't hear it. You will get used to it.

 

I had this....

Complained and 2 mods were done - SBC software update - did not fix it.

But then a physical replacement of a valve or pipes or something (on the merc list of mods) and finished - gone forever - hurrah!

Took about 3-4 hours at the dealer.

Don't stand for the noise / bad vibrations!

 

The software update is nothing more than a counter of brake applications so they can warn you to take it in for service when it gets 100,000 or something like that. It doesn't do didly-squat for the brake system.

The pulse dampener is what did the job. Look at your SBC pump and you will see that the two lines exiting the top have been modified.

In the process, you get a brake fluid change which reduced the herky-jerky operation I was experiencing in stop and go traffic. I still have it but it's not nearly as bad as when I got the car.