Chevrolet Repair: Clutch master and slave cylinder problem, clutch master cylinder, piston seal

Question
When I went out to start my 1988 Chevrolet C2500 pick-up today after it sat for about three weeks. The clutch petal went to the floor.  I checked the master cylinder fluid level and it was a little low but not dry by andy means.  I examined the master cylinder and the slave cylinder for leaks and didn't find anything to speak of.  I found some dampness on the bottom of the starter directly above the slave cylinder.  Perhaps the slave cylinder is leaking into the bell housing. I read one of your earlier answers and you suggested depressing the petal to the floor and sliding my foot off of it allowing it to spring back to the top twenty or more times to bleed the air out of the system.  This worked like a charm and now I have a clutch petal again. My question is why did the petal go away and how do I repair it properly.  If it failed once I have a feeling it will fail again.  Thank you for your previous answer that gave me the great advise allowing me to at least get my truck going for the time being.

Answer
Hi Tom, Thats great that you looked at old questions/answers to get the answer on your problem. I get repeat questions a lot.

   On your truck...a little leak will allow air to get into the system and cause this problem. So if you have a leak this is where to start. The other thing could be that it sat for a while and the clutch master cylinder rubber piston seal let air by. I would see if the problem happens again and if it does I would replace the master cylinder first. This is the easier one of the two to do:)

Have a Great Day

Mark