Ah, what a joyous topic! I've nearly 10 years collating as much information as I can - and my summary is that every brand of Slave Cylinder seems to have issues; it's just a case of stacking the odds in your favour so you'll hopefully be one of the lucky ones.
Observations so far (on the whole system)
- As Mike says, the clutch itself seems to outlive the Slave so no real issues there
- LUK Slave Cylinders seemed to fail quite regularly years ago, then they fixed 'something' for a few years as they were great, and yet their latest iteration is visibly poorly made and doesn't seem to last at all
- Borg & Beck Slave Cylinders were fantastic in construction of the body itself, however the bleed nipple assembly was poorly made leading to air entering the system. Still an issue in some I've seen recently but a lot still out there on many miles now
- The LUK Master Cylinder still seems prone to failure; I went through one every 6-9 months on my own 75 around 10 years ago and we've had lots of reports of the same. Fit the Tazu Mk1 Master via XPart or our original AP Master to resolve for good (well, a good few years at least)
The absolute best replacement Slave Cylinder is a new-old-stock item with the plastic pipework - these were fitted at the factory and we're still pulling some off cars in for work now.
Very (very) hard to find, though - I have a new one dated 2005 here at our clutch fitting garage and I treasure it with my life.
I'm open to discussion on the above (and I'm sure the 'holier than thou' crew with cast doubt on my findings) but these are my observations from what is just over 1,000 kits sold to date and regular follow ups / interaction with customers.
