The parts book shows that tractors sold in years '91 - '98 with a 13" clutch had the hydraulic release mechanism. 5640 included. If this is what you have, look for a bleeder vent on the left side of the bell housing(can be a bit awkward to reach on a cab tractor). Be aware that even after bleeding what seems to be all the air you can get, it may take several minutes of "pumping" the clutch pedal to get the thing to finally begin to operate. This wasn't one of "Ford's better ideas".
One more thing - the reservoir for the clutch and brake system takes a particular fluid New Holland sells as Hydraulic Brake Oil(I thinks it's a mineral oil, but not sure on that.) Don't use automotive brake fluid! If you have problems with air in the system, you need to check the fluid level. The supply port for the clutch master cylinder is slightly above the ports for the brake system so the clutch will stop working before the brakes do.