I bought a used '99 2.5L 5-speed OBW in '01. My clutch pedal loses it's ability to disengage the clutch as the car warms up. I suspect the master cylinder in the hydraulic clutch linkage.
Within a year of purchase, I noticed a problem with the clutch pedal, but more likely, a problem with the hydraulic linkage. The pedal does not return all the way up to it's upper clutch-engaged position. Everything operates correctly cold, but this condition develops as the car warms up and the clutch is operated more. Consequently, I almost never experience this condition in New England winters, but it develops very quickly on hot summer days in stop/go traffic or city driving when I am shfting a lot. Not suprisingly, I bought the car in February, so I never would have caught it during the test drive. Hmmmmm. At first, the pedal is just reluctant to pop back up over the over-center position of the pedal return spring. Eventually, the condition degrades to the point where I can not fully disengage the clutch and what action there is occurs in the bottom 2-3" of travel and the pedal only returns about half way. I doubt a worn clutch plate is the cause of this condition, but I'm sure that it is an effect.
I suspect one of the hydraulic cylinders is leaking (by-passing). The fluid becomes thinner as it warms up. Each time I operate the clutch, a little more leaks arround the cylinder leaving less in the line between the cylinders, until eventually, there is not enough left in the line to move the clutch plate adequately. If unused for a while, the fluid is eventually drawn back around the leaky cylinder by the clutch pedal return-spring pulling on the master cylinder end.
I think it is the master cylinder attached to the pedal, and I am just about to order one and try to replace it.
I have not ruled out air in the line or dirty fluid, nor have I pursued that theory, but I have a hard time explaining this condition by air or fluid condition.
Does anybody have any advice? Has anybody seen this condition.
Pete