ogm

Today when driving the C4 for a few miles i suddenly felt that the clutch-pedal didnt return to the same level as the brake pedal. This got from bad to worse within a few gearshifts, and i had to work hard to limp back home.
The pedal is now almost to the floor and doesnt relase the clutch anymore.

Any tips where to start ?


Odd Gunnar Moe
Norway

RoBB

I'd suspect a leaking slave cylinder, especially if you can pull the pedal back up and operate the clutch a few times before it gradually creeps back down with each push

Rob

ogm

I just removed the wooden floor board around the pedals to have a look around the mastercylinder. To get the board out i had to pull the clutchpedal back.
After that the clutch was perfect again. I tried to push the pedal 10-20 times but it would return to normal position everytime, even if i pushed it in for 15 seconds. Started the carm and the clutch was still perfect. However I dont think the problem is solved. I would like to lift the car at the rear to have a good look under the car. Any ideas where to place the jack stands, as i dont want to lay under the car with only the original jack supporting the car.

Any problems with oil levels if i raise the car only at the rear?

Odd Gunnar Moe

colo964

I've used a jack under the engine, near the drain plug (pad it with cardboard or a hockey puck). Place jack stands on the jack pads in front of the wheels. There are other methods, but I haven't tried them. I've also used ramps. You can see the clutch hose that way. You won't see much else even with the wheels off.

I think there is a return spring on the pedal. May be it snapped. There is an adjustment screw on it. See if messing with that yields any change.

ogm

I have ordered a new slave cylinder and hose today. I suspect it to be leaking, and as it was pretty cheap i guess it
is good to replace it anyway. I will use a power-bleeder.

Will the clutch pedal go to the floor and not return if there is a leak in the hydraulics? There is a pretty heavy coil spring on the pedal mechanism....

Can i also bleed the brakecalipers with a powerbleeder? (C4)
I dont have access to a Bosch Hammer if any fault codes will appear. Any thing else that should be checked when the car is lifted and the undercovers are removed?

By the way the engine looked remarkably clean in the cylinder areas, 100% dry, the engine have done 213000km/132462miles.

Odd Gunnar Moe

Indycam

The pedal roll pin ?

CraigyB

I had this on the way to Le-Mans, and it was the metal end stop plate I believe catching the pedal and holding it down. 6 Months later and the problem never returned.

38D

Very good suggestion. I've broken mine before.

ogm

I have to check the roll pin. Does it lock the "clutch-master-cylinder-push-rod-actuating-lever" to the clutch pedal shaft? I cant figure out why the clutch seemed to operate perfect after i pulled the pedal back. Is there any procedures changing the pin?

Odd Gunnar Moe

Indycam

https://rennlist.com/forums/showthre...light=roll+pin

https://rennlist.com/forums/964-forum/171418-clutch-pedal-roll-pin-failure-or-the-clutch-ain-t-dead-yet.html

Whats new with OGM ?

ogm

Thanks for your reply Indycam. I have read the threads in your link.
As no parts show up today either, I decided to remove the pedalcluster to investigate. The roll pin was OK. What i found was that the spring in the clutch pedal mechanism works via 2 intermediate pieces (part 13). What happens is that at the beginning of pushing the clutch-pedal, the spring works against your force, after i have pushed the pedal approx 2 inches the intermediate pieces working on the spring lever (part 16) tips over the pivot point and the spring actually pulls the pedal further in and hold it there. If this is the way Porsche have meant it to be I have no idea? The only force that can return the pedal from the floor is the hydraulic force working through the cylinders. If this is the way it is constructed, the spring will return the pedal to normal position, which can be adjusted by the screw (part 17). When the pedal is pushed to the floor, the spring (part 6) helps you hold the clutch pedal to the floor....
If there is a leak the pedal will not return. I found the reservoir level to be OK, but i guess there must be a leak in the slave cylinder. Thats the only idea left?

Odd Gunnar Moe

Indycam

If " I found the reservoir level to be OK" is true , you can't really have a leak . Do you have drips ?

The other thing is that the clutch spring that does the push back , might not be able to push back cause the levers / pivots in the bell housing are sticking .

ogm

There was some residue on the cover under the gearbox, which had no smell of oil and could be brake fluid. As this problem occured recently i guess the large reservoir on a C4 makes it difficult to determine a leak quickly.

Am i right that the clutch pedal spring acts as a servo after halfway movement to assist the force needed to hold the clutch pedal in?

Odd Gunnar Moe

Indycam

For a leak to stop the pedal from returning , the slave would need to be near empty . So a little damp is not a big deal I think . You would be seeing lots of fluid loss if you had a slave cylinder leak that caused the pedal to stop working . And the fluid would be gone from the reservoir as the fluid was pumped out of the slave cylinder . So no drop in the reservoir level makes me think that fluids not leaking .

The spring smooths the action of the pedal , I think . Same pedal feel , top to bottom .

I've offered this before and no one has taken me up on it , but I'll keep on offering .
Send me a ticket and I will come help you fix your car . I'd very much like to see Norway .
My buddy is going to be in berlin soon and he wants me to go over also , so if you need parts I could pop over to berlin , pick up any needed part and fly back with them .

JasonAndreas

All you need is a tiny bit of air to enter the system from a leak at a line fitting or the cylinder and the pedal will not return. There is a single pressure seal inside the slave cylinder that is probably passed its prime. When you bleed the slave cylinder follow the instructions that come with the bleeder and fill it, don't use it dry while trying to keep the reservoir full. Everyone that tries to bleed the slave cylinder that way ends up having to do it over. The reservoir outlet for the clutch is not at the bottom so what ends up happening is the fluid level goes below the outlet and tiny bit of air enters the system and they are back to square one with the clutch pedal not returning.

yes