First, but not always a clear sign that the clutch is time to change, is the squeak when pressing the pedal. Try to squeeze the clutch, and listen. If you hear creaking, then it's time to visit service center. Please note that the appearance of difficulty is not the surest sign of the output clutch failure. Sometimes the creaking of the mechanism, take, for example, the creaking of the rubber Mat that appears when you press the pedal. That is why you should make sure that the cause of the squeaking is the clutch and not anything else. But in any case, if it is possible to make a diagnosis, should do it. Additional feature which may be accompanied by the creaking is noticeable twitch of the pedal. His appearance already clearly indicates the need to repair or replace the clutch.
The most obvious and sure sign of the output clutch failure is the appearance of the characteristic smell of burning plastic. To confuse, or, worse, not notice the smell is almost impossible. Note that when the clutch starts to burn, you will not have a lot of time on its replacement. Once the smell of burning plastic, you should immediately go to the service center or you can change the clutch yourself.
You will immediately understand that a clutch is not all right, when will the problem with the gear shift. The clutch pedal will be much harder to squeeze, and then become hard to shift gears. As a rule, in the first place there are difficulties with the inclusion of first and reverse gears. And finally, switching gears will be quite impossible box and clutch just stop you "listen". Up to this stage it is better not to bring: as soon as you notice that the gear shift became difficult, to urgently engage in the diagnosis and repair or replacement of the clutch.