2001 Honda Civic clutch pedal travel

Transmission problem
2001 Honda Civic 4 cyl Front Wheel Drive Manual
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Hi,

When the car is cold (unused for several hours), the top half of the clutch pedal travel has no effect on clutch, free play only. The lower half of the travel is still useable.

As I drive and the transmission warms up, this free play gradually decreases and eventually all free play is gone, the entire pedal travel is effective.

Any idea ? anything to do with air in the hydraulic clutch line ?

Thanks for any help.