I know this may sound silly, but when my was popping, I just ignored it. Then one day at work I was pulling into a spot, I pushed in the clutch, and the pedal went to the floor. :--) Truck lurched forward and I had to shut it off to avoid from hitting another car. Where the rod from the master cylinder joins up to the clutch pedal has a little clip to hold it on. That clip broke and the rod fell off giving me no control of my clutch. So I would just check everything for safety sake.