Clutch Pedal randomly loses pressure

[prerunner1982]

Sometimes I will go to shift and my clutch pedal will have no pressure until it is almost all the way to the floor. It has always allowed me to shift, and I can pump the pedal to get the pressure back. Haven't been able to figure out why/when it decides to lose pressure, however I am not losing any fluid.
Any ideas?

[4.3LXJ]

Jon, your master cylinder is getting ready to go. You will have to replace it. I have found that NAPA replacements have a short rod on them and don't work right unless you lengthen the rod.

[prerunner1982]

Steve-is there adjustment built into the rod or does it have to be modified?

[4.3LXJ]

No adjustments. It is what it is. Hydraulic clutches are supposed to be self adjusting