how to bleed the clutch of 1984 928s Porsche to
You probably need a new slave cylinder. Check your brake fluid level (the clutch system shares the brake fluid) if it's ok, then it's almost certainly the slave cylinder. They don't last forever.
Search Porsche 928 Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Porsche 928 Experts