I've just stripped out a 1.25 zetec engine from a MK4 fiesta as the engine was knackered

I salvaged a 1.25 zetec with an auto box, split it down and i've since refitted the manual box to the running engine and refitted it all back into the car

The engine runs fine but i've ran into a problem with the clutch. I've bled the hydraulic line on it, 10 mins later i press the clutch pedal and it still works, selects all the gears etc and then if i leave it any longer or i have the engine running and go to select a gear the hyraulic line pops out of the gearbox where the clip goes around it.

I'm slightly worried the pressure is either building up too much or there's something seriously wrong causing it to pop out. I'm pretty sure the clip is engaging the line as you cant pull it out by hand, but operating the pedal it just goes straight to the floor nad pisses fluid everywhere

ideas?