Removal
1. The check valve is built into the brake booster servo vacuum hose.
2. Carefully release the vacuum hose from the servo unit, remove the rubber grommet.
3. Working backwards along the hose, release it from all intermediate retainers, then release the clamp and disconnect the hose from the inlet manifold/vacuum pump. Remove the hose assembly from the engine compartment. Do not attempt to remove the valve from the hose.
Examination
1. Carefully inspect the valve with the hose for signs of mechanical damage. Replace if necessary. The valve can be checked for proper operation by blowing through it in both directions. Air should pass through the assembly only in one direction - from the vacuum booster side. Otherwise, the valve must be replaced.
2. Check the rubber valve bushing for damage and signs of material aging. Replace if necessary.
Installation
1. Installation is carried out in the reverse order. Make sure that the hose is laid correctly and that the fastening clamp is securely tightened.
2. Firmly seat the bushing into the servo unit and thread the vacuum hose end fitting through it (try not to damage the bushing).
3. Finally, start the engine and check the relevant components for signs of air leaks.
(Text obtained from the website: SkodaBook.ru)