Q – My 996 Twin Turbo has a problem with the clutch pedal and clutch engagement. The pedal feels very odd and drops very low until I start the car then it pulses after the engine starts. Once the car is running, the clutch is difficult to engage smoothly. I have gotten used to both problems but I still wonder about them. When I let other people drive it, they stall the car and complain about how it works. Steve
A- Your car has an unusual clutch system since it is a turbo. On most cars, the clutch is manually operated with your left foot providing all the power to disengage the clutch and engage smoothly. In most applications, the system works fine and rarely has a functional problem. Sometimes the clutch pedal may squeak and after a few years, it may bind. The turbo, on the other hand, is a different animal. Since Porsche did not expect your left leg to have the strength of a gorilla, they designed the car with a power-assisted clutch slave cylinder.
The first symptom you describe is often due to a failure of the accumulator which stores hydraulic fluid under pressure providing power assist on start up. When an accumulator fails, the system will still work with the engine running and the pump functional. As soon as you turn off the engine, pressure drops and the pedal will feel odd. The rough engagement could be due to an internal clutch issue, the clutch slave power unit, or both.
The power-assisted slave unit carries a price tag of near $1,000 and a few hours of labor are needed to replace it. The unit is attached to the transaxle with a number of bolts and nuts that are extremely difficult to reach. Research online describes how to fabricate custom wrenches with a cutting torch and grinder just to get at them. The part was installed onto the power train before it was installed in the vehicle. Replacing it will be expensive, especially if you have a shop do the work.
An alternative would be to eliminate the power assist assembly and install a standard clutch slave cylinder. The part is amazingly inexpensive but there is no getting around the labor to surgically remove the original unit. It is not a simple bolt-in swap since you do have to block the pressure fitting, but that is not too difficult once you find the fitting that it takes. The strength needed to operate the clutch is manageable but noticeably stiffer. If you wife ever drives the car she won’t be happy with your choice. –MC