ment to ask in last response, but is it leaking the fluid out or is the clutch pedal jus hittin the floor? from wat ive noticed around here with my friends the slave cylinders tend to leak on nissan and if thats the case ya can replace it, or jus keep a small bottle of brake fluid with ya and refill the lil tank when its needed. if the fluid is at the same level and not leaking then its prob ur master cylinder.