So a few months ago my truck became extremely difficult to put into gear. At first I thought that maybe my clutch was gone, but when I released the clutch, it stalled out. I had my dad bleed it, thinking there might have been air bubbles, and it worked fine for about a week. Then it happened again, so I brought it to garage, where they bleed it and sent me on my way. A week later, I was back to square one. The garage had looked at the slave cylinder and said it was not leaking, and I had my dad replace the master cylinder, he bled it and did everything he was supposed to. It again worked fine for about a week. My dad seems to think that air got in when he did the master cylinder, and just needs to work its way out, but it's been a while, and I have gotten stranded one too many times at night in the city. Every time I lose pressure I fill the reservoir back up and he lets air out of the bleeder thing. I was wondering if it could be the slave cylinder, even though it does not appear to be leaking. And if I do the slave cylinder, should I do the whole clutch at the same time? Or are there other ways in which air can get into the system? I'm a little lost at this point.