Clutch stops working once car is hot

I have a 2001 Kia Sportage. Manual transmission.

For the past two days, once the vehicle has been running long enough to get hot, it becomes really difficult to shift. I think I’m losing the clutch pedal. For example, when in first gear stopped at a traffic light, the car will stall out with the clutch engaged (as if the clutch weren’t pressed down.) With the car moving, it’s physically very hard to move the gear shift.

Topped off the break/clutch master cylinder fluid, and it seems ok. Also took a look at the transmission fluid, and it is not low.

Any ideas?

Sorry I triple posted! It wasn’t intentional!

There may be a heat shield missing, allowing the clutch slave, line or some part of the system to get overly hot. Have a look around and see what you can find.

Sounds like a bad clutch master cylinder.

The problem is with the clutch master cylinder leaking internally.

When the underhood temperature is cold, the cup seal within the master cylinder seals and produces the proper hydraulic pressure to operate the clutch. As the engine heats up and the underhood temperature increases, it heats up the clutch master cylinder. This then causes the bore within the clutch master to expand where the cup seal no longer seals. This then allows the hydraulic fluid to bypass the cup seal where the proper hydraulic pressure is no longer produced by the master cylinder to operate the slave cylinder so the clutch no longer functions.

I’m having the same problem with my Nissan pickup, and it’s the worn out clutch master cylinder causing the problem because there are no external leaks in the clutch hydraulic system.