After driving thirty minutes clutch stops working

Hi and thanks for using 2CarPros. Com.

I need you to do a little diagnosing for me. What I think is happening is either fluid used to actuate the clutch via the clutch master cylinder or slave cylinder, is bypassing the plunger and once enough bypasses, it will not release the clutch. Hence, the car does not move. After sitting and cooling, the fluid returns and it works again.

Here is what I want you to do: Locate the slave cylinder on the transmission. When the engine is cold, have a helper press and release the clutch pedal a few times so you can see how far the lever moves and pay attention to its position when the pedal is released and depressed so you can compare it in the next step. Then, when it gets hot and no longer works, do the same thing. See if the lever is in the original position you saw when it was cold and if it moves when the pedal is depressed and to what degree of movement. Basically compare it to when it was cold. My biggest interest is if the slave is stuck in the engaged position when the pedal is released. If it is, there is a bleeder on the slave cylinder. Loosen it and allow a small amount of fluid to exit and see if the clutch works then.

Let me know what you find.

Take care,
Joe