ogm

Job done. Got the slave cylinder and hose today. Removed the heater hose and the left rear wheel to access the slave cylinder. The job would have been easier if i had 2 elbows on each arm. As i got it going it wasnt too bad.
I guess undoing the hose at the slave is not an easy job as it is difficult to get any torque on the wrench. I replaced the hose and took it off at the pipe instead. Mounted the new hose on the new cylinder before installing the cylinder. Have never used a power bleeder before. Borrowed one from a friend and the bleeding was done in 2 minutes. The old fluid was black. Should have been blue. The old slave didnt look too bad (the rubber boot was torn), the hose was also OK. Took the slave cylinder apart, I couldnt see any major fault. However the clutch works now, and I hope the hanging clutch syndrom never happens again.....


Is there any exact adjustment on the clutch spring adjusting screw?

Odd Gunnar Moe

JasonAndreas

Some of the new fluid will also turn black in about a weeks time due to the new hose.


Rotate the hex socket head bolt until there is 6mm of clearance between the screw and the pivot point. While you're in there you might as well make sure the clutch pedal travel is set to 150mm +- 5mm.





and if you notice a squeak coming from the slave cylinder in a few weeks or months time then pack the release fork receiving cup (if you didn't already) with Olista Longtime 3EP or an equivalent high-pressure grease.

ogm

I tried the car today after the slave cylinder job. First i adjusted the hex-screw for the servospring. I had to back it off about 3 mm to obtain 6mm between the hex-head and the plastic lever.For the first miles it was perfect. The suddenly the clutchpedal would not return properly. I just pulled it all the way back with my foot, and everything seemed to work. This seems like the symptom it all started with. (What happened then was clutch pedal to the floor but no clutch release) I checked the total movement of the pedal and it was around 145mm. When i push the pedal, there is almost no resistance the first inch of movement, then i can feel the hydraulic force/clutch. Is this normal?
Are we talking replacing the master cylinder as well? Have read at least 30 threads on this subject, most of them describe the same problem, but not any definitive solutions. My clutch drive-plate was replaced 6000km/4000 miles ago at a Porsche workshop.

Odd Gunnar Moe

JasonAndreas

You might want to try increasing the spring preload by increasing the spacing over 6mm and see if that makes a difference?

When the pedal was sticking to the floor was the clutch engaging properly and allowing drive to transfer from the engine to the transmission or would the engine just rev freely? There is always a chance the release bearing is hanging up but I would try bleeding the slave cylinder again before anything else.

Yes this is normal.

If the pressure seal on the master cylinder fails you should find brake fluid in the pedal area?

Indycam

master cyl ? If it was that the fluid was geting around the master cly seal , you should have leaking fluid . You state that you do not have leaking fluid . Have you looked on the front trunk floor for fluid ?
Has the ress level gone down ?

If you clamp off the rubber hose to the slave cyl , does the pedal get very hard to press down ?
Or does it go to the floor sometimes ?

ogm

I have backed off the screw, so the spring preload is less than it was.
The recommended 6mm, is that 6mm of threads beetween the screwhead and the plastic lever?
When this first happened, the pedal was to the floor and the clutch was still engaging properly (could not free the clutch). I have spoken to the main Porsche workshop in Norway who replaced my clutch a while ago. They say its likely to be the mastercylinder that fails as it have 2 seals and could have internal leakage. They also say Porsche have done several upgrade kits for the pedal mechanism (different lever which work on the mastersylinder and spring, with different ratio).
I have now ordered new mastercylinder + upgradekit for the pedals, roll pin and bushes...

Odd Gunnar Moe

JasonAndreas

The 6mm is measured between the back of the screwhead and the lever, around five american dimes (coins) stacked can be used as a feeler gauge.


If you get a chance take the old cylinder apart just to confirm the point of failure. A lot of times Porsche owners just replace everything and never figure out what the actual problem was.

The lever and the spring were changed when Porsche started delivering all 964s with the RS pressure plate. So with your new clutch it might reduce the pedal effort required but I don't think it will do anything for your problem.

When you have the pedal assembly apart there is a point that you can push the clutch pedal past that will take all the tension off the spring. Be VERY careful when "flipping/returning" it back over that point, the spring will cause the pedal to return with an enormous amount of force that will not only scare the crap out of you but can cause some damage to any body parts in the path of the pedal.

ogm

Parts arrived at last. Replaced master cylinder, clutch pedal lever and bushes.
Bleed the system. Same problem. Pedal will not return if pushed to the floor for 10 seconds. To test it i started the car on a level surface, selected 1st gear and pushed the clutch pedal to the floor. After 15-20 seconds the car started to move as the cluch started to engage. The problem seems to be that i loose pressure after some seconds. As I now have changed both clutch cylinders and the hose to the slavecylinder I guess i must have a minor leak somewhere between the master and slavecylinder. Have anyone else had this problem?

Picture from the parts catalogue.

Odd Gunar Moe

Indycam

OGM
If you are not loosing fluid , I really really doubt that you have a leak .
Its a very very very very rare leak that leaks air in and not fluid out .

ogm

I am convinced im loosing fluid, but it must be a minor leak, just enough to loose some pressure when the pedal is pushed for a longer time when backing out of the garage etc. I went for a 600 miles trip 2 weeks ago. After 400 miles and hundreds of gearshifts the emergency and brake lights came on and i had to top up the fluid reservoir.
Ill have to raise the car and remove all the covers so i can examine the pipes properly for leaking fluid.

When bleeding the clutch with a power-bleeder. Is it necessary to touch the pedal at all to get all the air out of the new mastercylinder?
I didnt do that.

Odd Gunnar Moe

deep_uv

No, not at all. Just pressurize the system with the power bleeder and out it goes.

Regards,

Steve

deep_uv

OGM, In addition to the clutch system circuit, you could possibly have a leak in the brake system circuit. The pickup for the clutch system is higher in the fluid reservoir than the brake system pickup.

Regards,

Steve

Indycam

"If you clamp off the rubber hose to the slave cyl , does the pedal get very hard to press down ?
Or does it go to the floor sometimes ?"
Did you try this test ?

"I am convinced im loosing fluid, but it must be a minor leak, just enough to loose some pressure when the pedal is pushed for a longer time when backing out of the garage etc."
I don't buy this .
If you lost pressure while holding down the pedal , the clutch would engage , you would have a symptom of the car being forced forward or backward .
For the pedal to stop working from fluid loss , you need to lose lots of fluid , you need to lose so much that the master cylinder goes "dry" . The fact that you can pick up the pedal and it works again tells that the fluid has not leak out . The lack of puddles , the statements that the fluid level in the res isn't dropping way low .

I fear that the real problem is inside the bell housing .

Try the test of clamping off the hose . Its called splitting the system . If the pedal never goes to the floor , stays up and firm , then the problem might be down stream from the clamp . If on the other hand the pedal goes down and stays down with the hose clamped , the problem is not down stream from the clamp .

ogm

Leak found!
The pipe connecting to the slave hose seems to have metal-to-metal contact with the transmission. What must have started as a minor leak seems to have escalated. Good to have found the problem. The job of changing the pipe will however not be an easy task I guess, as the pipe is routed/bent behind several other pipes and stuff. Have any other Rennlisters changed this pipe themself?
Does it come ready bent to fit or do you have to bend it to the right shape yourself?

Odd Gunnar Moe

JasonAndreas

Actually the process isn't that bad, just remove the center tunnel tray. You might have some problems with the connecting piece but if so just cut the old hard line close enough that you can use a socket on the old fitting instead of trying with a wrench.


Looking Rearward


Looking Forward

If you order the line (#964-423-109-01 $30USD) from Porsche it will come ready to install but if there are none available it won't be too difficult to fashion a replacement.