Farty brake noise from behind dash ('68 220)

[aircap]

Hi, all:

Today my Benz started making a new noise: When I press the brake pedal, a buzzing sound emanates from behind the dash (only sporadically, though), accompanied by a vibration in the pedal. Sometimes it's just a hint of a buzz, other times a long, drawn-out vibration. It's not coming from the wheels, it's specifically located directly in front of the steering wheel.

It seems like the brake pedal sinks to the floor a little more when it does this. Is this some sort of brake booster thing? Vacuum leak?

I appreciate any help you folks can give.

Thanks!

[aircap]

Ah...it is apparently the noise my car makes when it gets low on brake fluid. Topped it off and the noise went away. Nevermind!

[230/8]

Aircap:

If your brake fluid was low you should have seen a glowing brake light on the dash. Check your master cylinder and the floats inside to ensure the contacts are good and the light works. You would also be wise to bleed the brakes if the fluid got low enough for the pedal to bottom out. A power booster has been known to conceal a spongy pedal. Also, I would consider checking and/or replacing the check valve in the PB vacuum line. If there was a vibration it might be the source; maybe pulsing because of the low fluid level and the long pedal stroke.

230/8

[aircap]

Hey, 230/8:

The pedal never went anywhere near "bottoming out," but was notably softer. I will bleed the brakes in the near future, as I mean to check the rotors anyway. Thanks for the tips, as always!

[zeiglerr]

I'm guessing that the rubber seal in the vacuum booster accumulator has hardened and it isn't working smoothly. I rebuilt the one on my 59 220S years ago and it was very easy but don't know if yours is the same.

Reid