There is a fault elsewhere - possibly pressure switch on the lines or the solenoid unit on the rack pinion.
When a fault is detected the system defaults to no power assistance (fail safe mode) and the steering goes "heavy" - commonly happens intermittently giving an "on-off" feel while cornering.
The steering control unit looks for input from speed sensor (via the speedo), operation of stop lamp switch, clutch switch, parking brake switch, neutral switch - loss of any signal for a significant period leads to default.
Bleeding should be done with engine running and front wheels off the ground - turn from lock to lock adding fluid until no further decrease in level and no bubbling evident. Pump may click or buzz if air bleeding not complete. Don't overfill!
