There's a bleeder screw on steering valve under steering wheel but it will surprise me if air in system is the problem. I suspect that an o-ring is leaking on piston in steering motor. O-ring can be R&R by securely supporting frt of tractor then dropping frt axle & removing one side frame to expose the plug that holds pistons in motor. One also needs to drop spindle out of motor to remove pistons. Spindle requires timing when re-installed. Parts required are listed below.
1 ea R34748 Seal - SEAL,OIL ADD 34.22 USD