Clutch Issue 1987 Thunderbird Turbo Coupe

Hello,

My hydraulic clutch isn't operating correctly. I had a new clutch installed about two years ago due to the old one slipping and it worked great until recently. What is happening now is when I depress the clutch pedal it travels nearly all the way to the floor and just barely disengages the clutch. It works fine sometimes and other times I experience a very spongy feel just like air in a brake line would feel for the brake pedal.

I am thinking air may have gotten into the system somehow and what I need help with (as detailed as possible since I have never worked on a hydraulic system before) is how to solve the problem. I have been online but nothing is specific to my T-Bird, which I have owned since new. Looking under the dash things are extremely tight as well as on the firewall. I have not found a leak anywhere and the hydraulic reservoir remains full. All external parts are original.

Thanks in advance for your help!!!

Mike