yoni_d

Hi guys,

I have this strange problem that goes as following:
1. On cold start, the clutch pedal seems to be loose and there is a free travel of 50% of the pedal.
2. After starting the car there is still free travel and I cant (very hard) to put into 1st or reverse gears since the clutch doesn't seem to separate.
3. After about 10-15min there is almost no free travel and clutch works just fine.

It doesn't look like a hydraulic problem or a leak since if it does, the free travel would be constant. A friend of mine that also looked at the car thinks that the problem might be somewhere inside the clutch itself.
Perhaps anybody had something similar? The release bearing was changed a few years ago and it looks fine (there is almost no noise change when the clutch is pressed or not).

Any ideas of what may have gone wrong here?
The car is 928 S 4.7L 1980 euro model
Thanks!

928NOOBIE

Feels like it's not bled well. These clutches are real tough to bleed correctly.

I strongly encourage you to look into the clutch hose by Greg Brown at Precision Autowerks. He developed this hose due to the difficulty Porsche 928's have with bleeding the clutch.

davek9

When was the last time you bled and flushed the Brakes and Clutch w/ new brake fluid?
Do this before any other efforts to solve the issue.

yoni_d

Well, I dont think I bled the system for about 8 years since there was no oil missing or anything.
I will give it a try and see if it helps.
Thanks!

@928NOOBIE - I will look into it!

Schocki

Looks like either the master or slave cylinder have seen better days. Change the them both, bleed, done.

dr bob

The fluid is hyrgroscopic in the clutch system just like it is in the brake system. Since they share a reservoir, contamination in one is the same as contamination in the other. Flush and bleed both systems, using new dry DOT4 or better fluid. Note that this is an annual to biannual maintenance task, depending on how humid your climate happens to be. Note that Relative Humidity goes up as temperature drops with the same moisture in the air. So your cold garage will be much higher than the the air in your heated home. Keep that in mind as you mull the scheduling options. Those who subject their cars to tech inspections for HPDE and other organized track days know that six months is the max useful life of fluid in the car. Annual is a good street-car interval. My Honda asks for no more than two years between changes, but it gets the same annual treatment the 928 enjoys.

Mrmerlin

before you do any bleeding buy one of Greg browns flexible slave cylinder lines,
this will make bleeding a snap and prevent future clutch issues

yoni_d

Guys, thank you very much for your advises! I really apprentice it.
I will try to bleed both systems and see how it goes.

jbrob007

Yoni_D, Did you ever figure out the cause of this issue? What was your solution? I am experiencing these same EXACT issues in my 1981 Euro 5 speed. The clutch pedal is soft and does not disengage the clutch until half way down... Even then it's not FULLY disengaging and it will not shift at all when cold - lots of grinding to put it into any gear. So I start the car in 2nd gear and after driving in 2nd gear for a while the clutch pedal returns to full throw and the clutch disengages fully when pressed.

This is the tricky part, it does not do it when the outside temperature is in the 70's F...

Thanks!

Mrmerlin

JB I would suggest you do all of these things for your transmission longevity
Replace the MC,
and the slave cylinder.
Make sure to mod the MC cut down the tip of the piston so its length is 75MM ( they come at 80MM)
Replace the hard line and flex line with a long flex line,
this will make bleeding a snap,
and make it easy to remove the slave from the bell housing for maintenance.
NOTE Greg B and Roger sell these lines.
Check or replace the release arm bushing,
get a new blue supply hose for the MC to tank.
.
NOTE if after installing these parts you still have problems then clutch pack removal is advised.

to bleed the slave with the flex line installed,
first connect everything up ,
then open the slave bleeder .
once the bubbles stop, remove the slave from the bell housing.
Hold the slave so the bleeder faces up and then slowly push the rod all the way into the slave.
hold this for 30 seconds,
Then release the pushrod.
repeat this 2 more times,
Then install the slave.
you should now have a working clutch.
NOTE any indications of dragging mean,
your I plate needs adjustment ,
or the discs are sticking to the stub shaft splines,
either from lack of lubrication,
or from worn areas on the splines holding the discs.

jbrob007

Stan, Thanks! I have the new MC and will trim the rod down to 75mm. I also have new clutch discs & pilot bearing (read below). I believe Pete replaced the entire clutch hydraulic system when he owned the car (everything new) not more than two years ago. I'm probably over thinking this and need to bleed the system (again) but this time using the slave bleed technique. May also bleed the MC from inside the car if she still has a soft pedal. The thing that confuses me (not hard to do) is the soft pedal comes and goes with outside temperature or after the car warms up... You would THINK that air in the system would cause a soft pedal all of the time... We'll see how it goes and I'll report back.

In other news, I got a smoking hot deal on Euro CIS parts and custom exhaust from a BLS Club member. We're replacing my old crappy dual exhaust consisting of rusty long tube headers (manufacturer unknown) and some homemade looking dual exhaust with Thrush glass packs. The new to me system cam off an Euro with a complete custom SS exhaust system of MSDS long tube headers (test bung included), dual race cats & intermediates, with dual pipes to the tail pipe. The test bung will enable us to dial in the CIS system using a Wide Band O2 sensor. Might as well replace the clutch plates, pilot bearing & lube the stub shaft while were in there (since we have to drop the long tube headers & exhaust to do that job).

Afterwards, we MIGHT replace the entire Euro spider intake, runners, and all CIS components (throttle body, FD, WUR, fuel lines, injectors, etc).
Depends upon how the car runs with the new exhaust and our ability to dial in the old CIS system. We have a couple of guys here that know how to adjust CIS using this method so I may learn a thing or two in the process. Mike likes to say "CIS is Da Devil !!" I tend to agree

Thanks again!

UKKid35

I have experienced a similar issue when the car has been left unused for several months

Initially the pedal bite point is much lower than usual, and the pedal is lower at rest (level with the brake pedal which is where I'd like it to be)

However after the drive-train has warmed up the pedal returns to its usual high position at rest, and with a higher bite point

It then stay like that for weeks, until the next time I neglect the car for several months

I can't see how this can be a bleed issue

I will flush the fluid over the summer, as I haven't done so for some considerable time (although the brake fluid was done a few weeks ago)

jbrob007

Sharks,

Here's what we found and what we did to remedy the situation. The clutch plates were just above minimum spec (barely) so the intermediate plate "H" adjusters were all the way down. We had to BP Blaster the H ad justers & exercise all three to get them to move properly. The bigger problem was splined shaft was buggered up where the 1st clutch plate sits / engages the flywheel. It takes the initial brunt force so it's not an uncommon wear item after 130K miles. Unfortunately, a new one costs $600. Fortunately, I got a good used one & new TO bearing from a local club member who's parting out a car. Got new clutch plates from Roger and replaced them, splined shaft & TO bearing, cleaned up the intermediate plate & pressure plate with emory cloth, and had the flywheel turned. Lubed the splined shaft with optimal grease and put it all back together - PERFECT! The Torque Tube bearings have already been replaced with Super Bearings (I can see one of them a foot in from the front opening) so we abandoned that part of the job.

Replaced the old headers & homemade dual exhaust with MSDS headers (with O2 sensor bung) & a custom SS 2.5" dual race cats to one 3" exhaust and two intermediate mufflers (also off the track car) which required fabricating new hanger brackets and installing extra heat shield for the tunnel. Losing some low end torque (less back pressure w/ 3" exhaust) but gaining top end HP. Sounds AWESOME... like a track car! No drone as of yet, but it is LOUD when you press on the "loud pedal" up to 5 - 6K rpm. It runs & shifts great. So, PROBLEM SOLVED!

Next step, we'll use header bung w/ the Innovate O2 Wide Band sensor to dial in the CIS.