DSMblue

I have been experiencing a soft brake pedal when the temperature is cold (35 degrees and below). Thought that I had a bad master cylinder. Yesterday and today, temperature is above 50 degrees, brake pedal is fine. Now I am confused - what could be causing the soft pedal in cold temperatures? No leaks anywhere in the system that I can find.

PorscheDoc

old brake fluid having too much water in it would be my guess. I would bleed the system with all new fluid (suck the reservoir dry with a syringe or something before adding new fluid).

DSMblue

Went ahead and replace master cylinder and flushed 1.5 liters of ATE Typ 200 fluid through the system, all appears well now. Just have to figure out why the clutch pedal doesn't return to top...that has been bled three times now, and has new master and slave cylinders.

PorscheDoc

Pump the clutch pedal about 100 times bringing it back all the way to the top each time, it will slowly get the the point where it is fully returning. Then bleed it again and the repeat the cycle until the pedal does what it should after your bleed attempt.

DSMblue

Answer on clutch pedal was master cylinder rod on replacement master cylinder was shorter in overall length than the original unit. My friend (certified Porsche mechanic) replaced rod with an original and adjusted travel, everything is fine. Now on to replacing e-brake cables, and whatever comes up next on the list of never ending things to do!