[madmaxx]

i assume you checked the clutch fluid level? strange no leaks but you are loosing hydraulic pressure. slave cylinder super cheap. don't let clutch reservoir run empty when you replace use cling wrap under the clutch master cylinder cap, if not you will have to bench bleed the clutch master cylinder, in other words remove it. I would check level, if level is good than bleen the slave cylinder just like a wheel cylinder on brakes very easy and quick with two people if that doest work post and i am sure somebody has another idea. I had an old triumph spitfire that leaked internally on the master cylinder but than again it was 20 years old.