LandSeaAir

I was driving on the highway today in my 2008 C300 4matic and suddenly I press the brake pedal and it was totally stiff as if the car was off. It was scary because the car in front of me stopped quickly and I really had to hit the brake to get the car to stop.

The pedal stayed like that for another 10 minutes and then suddenly it was okay again.

Anyone have any idea what this could be? Related to the brake fluid needing to be changed?

I had the brake booster replaced under warranty about two years ago, the brakes worked fine up until now.

RLE

Sounds like an intermittent vacuum leak to the power brake booster. Talk to the dealer about this even though the car is out of warranty, possibly. This is a safety issue so don't mess around. You better hope it isn't the ABS unit$$$.