Here's What Happens When You Ride the Clutch
The problems can range from small-time problems to full-blown failure.
Riding the clutch is something all manual drivers do from time to time, whether we admit it or not. It may be excess slipping when moving a heavy load, or just lack of attention. The real problems don't come from occasional additional pedal time, but rather, when you habitually keep the third pedal depressed just enough for the throwout bearing to engage.
While crawling around the internet this morning, I happened to come across a video that hit home. A few years ago, I purchased a Subaru Legacy GT—or, as I liked to call it, "the family man's STI." The car was a bag of problems; from putting two motors in it to fixing this very same issue that was caused by a previous owner, there was always something to fix.
One of the early signs that the Legacy's throwout bearing was starting to fail were chirping noises when disengaging the clutch. A simple fix was to lubricate the input shaft on which the throwout bearing sits, but that's assuming it's not too late. Eventually, the throwout bearing's movement will cause it to eat away at the input shaft. PDM makes a snout sleeve kit (which you can see around the six-minute mark in the video) that sits over the snout with an oversized throwout bearing.
The particular failure featured in the video was a bit more severe. The car even moved under the starter's power with the clutch depressed; something was seriously borked. As it turns out, the owner did not address the bearing before it seized and it actually broke some of the clutch fingers off of the pressure plate. Take a look at the carnage in the video below.
Moral of the story? Keep that left foot off of the clutch unless you're ready to press it in. Alter your driving habits before they result in a full-blown failure.