I have an act 6 puck clutch put in my 88 gtu. I have had it in for about 5 months now and have had no problems. Recently I noticed that the clutch pedal tends to sink sometimes. I don't know if its because its just cold or whatever. If anyone knows what may be the problem lemme know.

 

Clutch fluid problem.
Maybe you have air in your system.
Did you check under your car for a hydralic leak?