Hy Charles Pretzer, I think you should try bleeding the brakes. Do you have a manual for your truck? If you don't have a manual I'm sure one of the helpful gentleman confusilator gurus on here will provide a link to one. While bleeding keep checking for leaks in the metal tubing and rubber flex lines. On a truck of this age I would do a complete brake system overhaul just to make sure everything is working as it should and you and others on the road around you are safe.
