The way to test to see if the master has any pressure on it when not pressing the pedal is easy..... Once the car is warm and the pedal starts changing get under the car and press the clutch fork against the slave pin by hand.... The slave piston should push in with a small amount of resistance and fully collapse. What your doing is pushing the fluid back into the master.....If the slave will not compress only two things are possible...... 1. The master has the hole closed and is building pressure from a incorrectly adjusted pedal. 2. The slave is already compressed fully because the pressure plate in not made correctly and the geometry of the clutch fork is wrong....In this case as the parts heat up and expand it can not push the slave in and it is putting pressure to release the clutch and this will also cause the pedal to move. If this is the case the slave pin could be shortened to compensate for the pressure plate fingers being too far forward as a band-aid.
