Almost ever since I've owned my 1968W200 (since 82), the clutch master cylinder has been finicky. What I mean by this, is if I drive my truck in stop and go traffic where I'm constantly shifting after awhile the clutch pedal will suck up air and get a spongy feeling. I've noticed that if I press and depress the clutch petal slow, it won't be as bad. I can usually work around this problem and after a while the clutch pedal will feel "normal" again, but if I let anyone else drive the truck, forget it. They bugger it up and then I have to work the clutch pedal as described up above. I've replaced the master cylinder with brand new NAPA parts and slave cylinder as well numerous times and haven't been able to solve the issue. I've read on the forum that NAPA had quality issues with the clutch master cylinder, and I'm wondering if I just so happen to be one of the "lucky" ones to get three bad units. Last time I've replaced it was in 1996 and the first time I replaced it was in 1988. Prior to 1988, as I can recall, the clutch worked fine. Fortunately at the time the master cylinder was life time warranty, so I've been able to get them for free. Also, the master cylinder isn't loosing fluid. Question: Has anyone else experience similar problems? Is there a better brand to purchase a clutch master cylinder from? What success has people had using NAPA clutch master cylinder. Any help would be appreciated. Thanks Mike M.