Mercedes Benz repair: 1983 300sd questions, poor vacuum, vacuum leak

Question
I have two...among many!
Is there a way to troubleshoot a hard brake pedal at low
RPM?  I just noticed the pedal stiffening in city traffic, but
improving once teh trans has had a chance to shift into 3rd
gear.  
Also, I have had recent trouble restarting my faithful friend
after a short trip (refueling or convenience store) It now
takes 2-3 attempts.  Any thoughts?  THANKS!!  

Answer
The hard brake is vacuum not getting tot he booster. There is either a vacuum leak or you have low vacuum at idle. This could also be causing your starting problem. You could need a valve adjustment or you could have bad vacuum or a leaky valve that causes poor vacuum at an idle. You could need a valve job.