After removing the dirt around the servo mechanism, remove the circlip.
Remove the servo switch.
Loosen the lock nut.
While holding the servomechanism piston from rotation with a special key and a torque wrench, tighten the adjusting bolt to a torque of 10 Nm. After releasing in several steps, tighten the adjusting bolt again to 5 Nm. Loosen the bolt again 2-2.5 turns.
Holding the servomechanism piston from rotation with a special wrench, tighten the lock nut to the required torque - 25-32 Nm.
After installing the new O-ring into the groove around the servo switch, straighten the O-ring so that it is not twisted.
Install the snap ring.