1990 300SEL brake problem?
 

Yesterday I was driving around for about 3 hours running errands. Mostly highway with 3 or 4 stops for 15 - 20 minutes each ( engine was turned off). Brake pedal was normal. As I was heading home in city driving, I noticed the pedal went about 2 inches farther down than normal before braking action occurred. It happened quite suddenly. One stoplight it was fine, next light (2 or 3 blocks) I had more pedal travel. Brakes still stop the car fine and feel solid. Master cylinder reservoir level is normal.
Thanks in advance for your ideas and comments.
Ken

Could be as simple as needing a fluid flush. Brake fluid flush should be done every 2-3 years.