I HAVE A 1992 LEXUS SC300 5 SPEED. WHEN I LET THE CLUTCH OUT, IT SOMETIMES ONLY COMES OUT ABOUT HALFWAY. IF I DO NOT PULL IT THE REST OF THE WAY OUT WITH MY FOOT, IT WILL PULL ITSELF ALL OF THE WAY IN TO THE FLOOR. THE FLUID RESERVOIR IS FULL AND IS NOT LEAKING.
It sounds to me like either your master or slave clutch cylinder is shot. You should replace both together anyway.
What’s happening is that when the piston pushes the fluid (or the fluid pushes the piston if it’s the slave) the fluid is passing by the seal around the piston.