My accord keeps losing clutch fluid, loses more during around the town driving, inspected for visual leaks and none found...replaced clutch master cylinder cap and bled slave cylinder. fluid was dark but bled until clear fluid came out...pedal was fine for about a week, then I noticed the pedal became soft again, looked at the master cylinder and the fluid was low again. Im not sure where to go from here.. any ideas?

 

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I actually only replaced the cap, I didn't replace the whole unit.