Checking pistons and thrust plate for wear

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2009 Audi A4, 2008 Audi A4, 2007 Audi A4, 2006 Audi A4, and 2005 Audi A4. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Inner Running And Sealing Surfaces Of Thrust Plate And Pistons

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Remove pistons - 1 - from thrust plate - 2 -.

Check thrust plate - 2 -

Check thrust plate running and sealing surfaces - arrow A - for wear.
Check thrust plate running and sealing surfaces - arrow D - for wear.

If running or sealing surfaces - arrow A - show grooves, scratches or scoring, thrust plate - 2 - must be replaced.
If running or sealing surfaces - arrow D - show grooves, scratches or scoring, thrust plate - 2 - and pistons - 1 - must be replaced.

Checking pistons - 1 -

Check seal - arrow B - on outer piston circumference - 1 - for damage.
Check running surface - arrow C - on interior piston circumference - 1 - on shaft.

If seal - arrow B - is damaged or piston running surface - arrow C - shows grooves, scratches, scoring or uneven thickness from wear, piston - 1 - must be replaced.