[special-K]

This isn't exactly the same, but may help with some understanding. I had a roundy round situation with my old '92 K3500 with NV4500. I lost pedal and replaced the slave cyl. (NAPA). Pedal went to the floor again, got a replacement, pedal to floor, so I replaced the master cyl. (NAPA) Pedal to floor, replaced line (GM). Pedal getting low, noticed fluid on inner fender, discovered a stream I couldn't see but put my hand between wet spot and M/C and got sprayed. Fluid was coming through the plastic body. Replaced with another NAPA M/C and same thing. I got NAPA to refund money (warranty is replacement only) so I could buy GM parts. Still lost pedal after that. Took a look inside the bellhousing and discovered the ball stud the clutch arm pivots on was worn way way down to nearly 1/2 a ball. It was causing the cylinders to over extend and blow themselves out. Truck had around 300k on it and figure that metal to metal wear surface gets no lube