Case 1150 can't tighten track

I am purchasing a case 1150 track loader from a friend. The machine is a 1972 model with only 300 hours on it.
The right side track is loose and we can't get the adjuster to take grease. We have taken the zerk and check valve out they are both clear. When we took the check valve out some grease came out. Some of it was solidified. When we took it out the adjuster moved in slightly. But it won't take any grease. The grease gun just locks down. Any tips or tricks on this would be appreciated. Thanks