Q&A

 Master

Maybe the line between the master and slave has a slight leak and is letting air into the system

 Journeyman

I agree with Valleyautotech. If you don't find a leak you might try this bleed prodecure,

Fill the reservoir with new brake fluid. Use Delco Supreme® Brake Fluid (GM P/N 1052535) or equivalent.
Raise the vehicle.
Depress the clutch pedal (hold the pedal down).
Open the bleed screw on the concentric slave cylinder in order to expel the air.
Close the bleed screw then release the clutch pedal.
Important: Ensure no air is drawn into the clutch system.

Repeat steps 2, 3, and 4 until all the air is out of the clutch system.
6.1. Check and refill the reservoir as needed while bleeding.

6.2. After bleeding, pump the clutch pedal several times. If the clutch engagement is not satisfactory, repeat the bleeding procedure.

If the previous procedures are unsuccessful, perform the following steps.
7.1. Remove the reservoir cap.

7.2. Pump the clutch pedal very fast for 30 seconds.

7.3. Stop pumping and let the air escape.

7.4. Repeat this procedure as necessary.

Lower the vehicle