Hello there.
Today I started up my 95 S350 and after idling like 2 minutes I put it in reverse and drove back about 20 feet to get it out from my yard in the street.
What really surprized me was when I tried to brake, the brake pedal was like stone, and even though I pressed hard I still couldnt move them even slightly.
I had to take the shifter out of Reverse and I hit the handbrake, and that stoped the car from hitting the wall behind me.
After this I pressed tried to press the regular brake pedal and it made a noise like something releasing air and then it went all the way down easily.
After pumping the brake pedal about 3-4 times it started to work again.
I drove the car for about quarter mile and hit the brakes all the way down several times, and everything seemed to work fine.

Is my W140 doing me a favor and warning me to change anything in the brake system, maybe a new pump or something?!

Thanks

Sounds like a problem with your vacuum system to the brake booster. Think the S350 uses an engine driven vacuum pump, no?
Without proper vacuum to the brake booster, the brakes will be extremely hard.

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KenP

1996 S500 W140 Coupe

May need a vacuum pump. Check to see if it is providing vacuum.