I have a previous thread on this issue:
http://www.peachparts.com/shopforum/sl-forum/325268-brake-issue-77-450sl.html
Today driving home from work my brake pedal once again lost pressure, and went to the floorboard with just enough "umph" left to stop it. Pumping the brake several times brought it back to normal, but had to do this several times to get it to stay this way.
I see in the previous responses that air in the system could be a possible culprit - would the above scenario be possible due to air in the system? I soooo don't want to go through the whole master cylinder replacement again....
And are there any other reasons? This has now happened with the old master cylinder and the new master cylinder.. all other parts are okay to the best of my knowledge, fluid is full, etc.
And also - how would I know if it's the brake booster?