I have an 89 wrangler that is somewhat new to me. The clutch line continues to get air in it and I lose pressure. Each time I bleed the line it is good for about a day. The grommet on the master cyl cap was a little messed up so i replaced with a similar o ring - but I am not getting leak from there. I can't seem to figure out why this would happen, any thoughts?  

WELL SOMEWHER BETWEEN YOUR MASTR AND SLAVE CYLINDER YOUR GETTING AIR...CHECK THE FITTINGS FROM THE LINE AT BOTH ENDS...I M NOT SURE HOW THERE JEEPS SET UP IS FOR THE CLUTCH BUT ON MY 93 CHEVY THE ROLL PINS THAT HELD THE LINE ON BETWEEN THE TWO WAS WORN BAD AND LEAKED THERE SO I REPLACE THE LINE,MSTR AND SLAVE CYL. OH AND ONE MORE THING, IF THE MSTR CYL IS MADE OF PLASTIC,( WHICH MOST OF EVERYDAMN THING IS), CHECK WHERE THE TWO HAVES WERE MOLDED TOGETHER AT THE SEAM CAUSE I REPLACED ONE AND THE ONE I GOT HAD A SEAM THAT WAS BAD YOU COULD PUT PRESSURE ON THE SYSTEM AND YOU COULD SEE IT SWEAT!  

Is there a leak anywhere?  

You might want to check the slave cylinder. It could be leaking at a seal. You would notice that it would be wet with brake fluid. If it is wet and always has been. Then clean it with a can of brake parts cleaner and hit it with some compressed air to dry it. Then try using it a few times to see if you can spot the leak if it has one. Also if the fluid is contaminated with moister. (sense you said that the cap seal was previously bad).Brake fluid is very supsetable to moisture. This will make it act like the conditions you are reporting. In this case you would have to drain and flush and refill with new dot3 fluid.
ASE Tech  

Thanks for the help.  I don't see any leaks from the master down the lines to the slave.  The slave cylinder is internal, I have taken off the cover and don't see any fluid here either (not really sure how else to check this).  The other strange part of this is it always seems to get worse as the engine gets hot - or after driving around for a bit?  

If you have the same slave I do I think I know what the problem is.  Do you have good pressure when the clutch pedal is pushed all the way in or does your tranny grind a little when you put it in gear.  My external clutch slave is getting worn and it gets air in it around the rubber grommet inside the slave.  I think the only fix would be a new slave.  Just my advice.