If you replaced your clutch fluid and it still looks like the photo below then you most likely need to get a new Master Cylinder. The new cylinder is best paired up with a one-piece stainless steel line. Even better to replace your slave cylinder as well.

Master Cylinder

Part Number: 30610-3Y007
Price: $100.00
Order Link:https://www.nissanpartsdeal.com/parts/nissan-cylinder-assy-c~30610-3y007.html?vin=&make=Nissan&model=Maxima&year=2002&submodel=&extra1=&extra2=&filter=(2=VQ35DE;3=USA;4=SES;5=MT)

 Slave Cylinder

Part Number: 30620-AU400
Price: $91.00
Order Link: https://www.nissanpartsdeal.com/parts/nissan-cylinder-assy-c~30620-au400.html?vin=&make=Nissan&model=Maxima&year=2002&submodel=&extra1=&extra2=&filter=(2=VQ35DE;3=USA;4=SES;5=MT)