Stoney1918, what you said is true for the 350 utility. I put a wire brush on a drill and cleaned all the metal. I clamped vise-grips on the little knob and wiggled it a lot. was wearing the little knob down. It looked like it should wiggle out, but it was hung up. Maybe, I thought if I started the tractor and used the hydraulics, that it might push the cap out. As soon as I started it, immediate hydraulic system pressure popped the cap, a collar and the spring out of the hole....along with a fair amount of oil. The bottom of the seat took the brunt of it, and protected me from most of the oil. The collar and spring were laying on top of the hydraulic reservoir, and the cap was laying on the ground behind the left rear tire. The good news is that its out, and I will go by the Case IH dealer tomorrow to try to run down the O ring and maybe a new cap.
Thanks all for your responses.
Have a great Thanksgiving and Merry Christmas.