Take the cylinder off and take it apart. Take the seals and orings to your local hyd. shop. Or just take the cylinder to your local shop and let them rebuild it. I rebuild my own Mahindra cylinders. My backhoes seals and orings are way cheaper buying from the local hyd. shop. A lot faster too. But I take my excavator's cylinders to the shop and let them rebuild those huge cylinders.
hugs, Brandi