Arthur,

As you rightly point out, a combination of glazing, some wear and possible hyraulic problems could all cumulate to cause clutch slip before the wear limit is reached. The issue with the hydraulic hose was in the back of my mind when I considered the possible cause of my problem. I am aware of constricted brake hoses preventing brakes fully releasing and as you point out, a similar condition with the clutch hydraulics could prevent the slave cylinder fully returning leading to slip. Thanks for the suggestion. I will investigate that as a possible cause of the problem.

Greg

Another observation
 

Something else I have noticed. When the car is cold (ie. when driven first thing in the morning) the clutch takes up where you would expect it to. As everything gets warmer the take up point gets higher. On the occasions when I have detected some clutch slip, it has always been after driving the car for maybe over an hour in warmer weather conditions. These conditions result in the clutch engaging right at the very top of the pedal travel. This sounds to me like a hydraulic issue, almost as though the fluid expands and can't get back through the master cylinder to the reservoir. Possibly the constricted hose problem? I would expect that if the clutch was worn out, it would not be affected by temperature, and the take up point of the pedal would not change. It definitely only slips when the take up point gets too high.

As the take-up point gets higher, the clearance is eliminated and the possibility exists that the hydraulics are preventing the clutch from full engagement. Hence the slippage. This could occur in the slave, the flex line, or the master. I think at a minimum you should replace the flex line and thoroughly flush and bleed the system

Chuck,

The more I think about this, the more tempted I am to start with hydraulic items like the flexible hose as you suggest. It would be a pointless exercise to replace a clutch that only slips because the hydraulics don't always allow full engagement. What a pity space is so tight around the slave cylinder between the transmission and floor. Oh well, I guess it is still easier than removing the transmission and everything else that is required to replace the clutch.

Greg

I second the hydrolics as a cause. I once had a master cylinder that would not let the fluid release back through the system. It kept building up pressure as it was used.