DatsikWS6

Hey all, ok so the other day, I come to a stop sign, put the clutch in and come to a stop. when I go to take off again, after about an inch of releasing the clutch off the floor, the car stalls. so I go to put the clutch in to restart the car and the pedal goes almost 3/4 of the way down to the floor before I feel some resistance. I had noticed the week before this happened that the pedal had gone down a good two inches really easy before I felt any pressure. when I got home, I checked the fluid reservoir and the fluid was black. im not sure if that is the problem or if its something else. I figured that if I replace the fluid and then observe the master cylinder while someone pumps it to see if that is the problem. But before I do anything, I just wanted to see what some of you have to say. do you think that replacing the master cylinder will fix it or am I going to need a new clutch? thank you!!