93 f150 2wd with m5r2 trans. Clutch pedal went to the floor. Had to pull it up with my foot. Pumped it a few times and it works. Fluid is full. No leaks underneath. Drove it to the first stop light and while I was holding the clutch pedal down it stuck to the floor again. Lifted it up, pumped it , and went on my way. Bad clutch master cylinder??? What do you think?

 

the master can be getting bad... try changing the fluid first.

Mine does that every once in a while but it is still going.... 2 years now

 

The majority of people with this problem when it shows up out of nowhere is a bad slave cylinder. Tranny removal and then two bolts hold it on. there should be no reason any air is in the lines unless it was ran dry or has a leak. If it comes back by the next day after a flush, most likely a slave.

 

Unhook the line from the slave, it caps itself off. Pump the pedal, if it gets stiff until it won't press down anymore the slave is bad. If it doesn't the master or line is bad.