964 C4 clutch problem

JB · 01-04-2009, 03:34 PM

My 1990 964 C4 will not disengage the clutch unless the pedal is pushed to the floor. As long as you diligently push it to the floor it will shift just fine. The clutch does not slip and the car is generally pampered as it is my wife's daily driver. I have researched this on this forum and quite a few have had this problem but no clear answer is revealed. I have changed the master and slave cylinders, pressure bled several times and no change. According to the manual, there is no adjustment other than the helper spring. Does anyone know of a probable cause and fix?

Hans57 · 01-05-2009, 07:18 AM

Quote:

Originally Posted by JB

My 1990 964 C4 will not disengage the clutch unless the pedal is pushed to the floor. As long as you diligently push it to the floor it will shift just fine. The clutch does not slip and the car is generally pampered as it is my wife's daily driver. I have researched this on this forum and quite a few have had this problem but no clear answer is revealed. I have changed the master and slave cylinders, pressure bled several times and no change. According to the manual, there is no adjustment other than the helper spring. Does anyone know of a probable cause and fix?

Does this happen with engine loaded or unloaded when you notice the problem?

bazar01 · bazar01's Garage

Have you checked the slave cylinder rubber hose? They tend to expand when pressurized due to age. If that is not it, only thing I can say is the clutch disc could be hanging up on the input shaft splines due to rust or absence of lubricant thus not allowing the clutch disc to release even when the pedal is fully depressed..
Did you try rev matching or blipping the gas just to get in and out of gear?

JB · 01-05-2009, 08:21 AM

The problem I'm having is consistant from a stand still, putting it into first gear to upshifting or down shifting into other gears while underway. To get into any gear, the clutch pedal has to be fully depressed hard against the floor and then the clutch engages immediately upon releasing the pedal off the floor. There is no problem as long as you press it hard against the floor. Other 964's I've driven start their clutch engagement at least 1 - 2 inches off the floor. I'll check and replace the hose you mention and see if that is the culprit.

thanks for the input.

group911@aol.co · 01-05-2009, 05:48 PM

I have seen air in the line do it. Not sure if you have recently done something that would cause air to get in but you might try bleeding it.
The 964's are pain to bleed. The loop in the line right by the pedal assy is where the the air gets trapped.

Hambisa · 01-10-2009, 07:49 PM

This can also result from the roll pin in the clutch pedal assembly being worn. Repair requires removal and disassembly of the pedal cluster, rather a PITA, especially the first time you do it. Check if this might be the problem by removing the board over the cluster and testing to see if there is any noticeable play between moving the clutch pedal and activation of the lever that pushes the master cylinder plunger. If you have to replace the pin, be sure to use the opportunity to also replace all the nylon bushings in the assembly and it will all be good as new.