Without any info at all, I do wonder if it has a hydralic actuator, and
old brake fluid absorbs water, which can boil and expand, after about 30
minutes of running, and partially release the clutch, even if no foot is
on the pedal!
Solution for that is to drain, replace, bleed fluid in that small
system. Also check that the free play is adjusted properly, so the
pedal has the half to one inch free play at the pedal.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.