Clutch Master And Clutch Slave Cylinder, Checking
WARNING: This page is about a different car, the 2017 Volkswagen GTI, 2016 Volkswagen GTI, 2015 Volkswagen Golf, and 2015 Volkswagen GTI. However, it is still accessible from the selected car via links, so may be relevant.
Before replacing the clutch master cylinder due to an assumed defect, perform the "Guided Fault Finding". Refer to Vehicle Diagnostic Tester first.