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Join Date: Jul 2006
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Too Much Clutch Pedal Hard Slack

Hello Folks,
I have had this problem for years and just "dealt" with it, but I'm done with that.
The clutch on my 1983 Porsche 944 has always engaged and disengaged properly, but I have always had the same problem shown in this guy's video.
https://m.youtube.com/watch?v=jcoghewGcqE

I have always had the normal 3mm of clutch freeplay, but then the pedal drops several inches and will sit there until I push the pedal again to engage the clutch. In this position, the pedal sits about 1" to 2.5" from the floor.
I can then pop the pedal up to the original position by getting my foot underneath the pedal, but I could always leave the pedal in the lower position and still use the clutch.

I am currently replacing the Master Clutch Cylinder and found that the seals on the Slave are leaking so that will be replaced, as well.
I would like to resolve this pesky pedal problem once and for all.
I have replaced the master brake cylinder and slave cylinder several times over the past 16 years or so, and even replaced the entire clutch system about 12 years ago, but this is the first time of replacing the Master Clutch Cylinder.
I just had firewall welded at the MCC opening, but there doesn't appear to be any drastic increase in the thickness of the firewall.
The distance from the clutch pedal clevis to the firewall is 160mm. The distance of the spring assist is 60mm.
The travel distance of the MCC push rod from the pedal up position to the pedal drop position is 1.5mm while the clutch engagement to floor position is 12mm. This distance should actually be 15-18mm. The 12mm of travel is probably being caused by the leaky slave cylinder, but I am not 100% sure of this until I replace the SC.

Any help is appreciated.
Thank you.
Old 07-14-2019, 01:59 PM
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9FF 9FF is offline
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Itís wise to replace the master, the slave, the master to slave hose and the blue hose at the reservoir. Any of those parts can introduce air into the system and give you the issue you have and no amount of bleeding will permanently fix it.

Problem, especially with the rubber parts of the two hydraulic hoses is that they become porous with age and suck in tiny amount of air into the clutch hydraulics each time you use the clutch. The hose between the master and slave is the main culprit and often overlooked, Iíve seen ones that were obviously original to the car and should have been replaced last century.
Old 07-14-2019, 02:22 PM
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Thanks for replying.
I found myself in the same situation and experienced the same problem - even with a new master brake cylinder, new slave cylinder, and new hose.
I have been driving with this same problem for over a decade.
The only difference now is the decreased travel distance of the pedal (right after the clutch engages), but I believe that is being caused by the leaky slave cylinder.

Last edited by SpidrVII; 07-14-2019 at 03:25 PM.. Reason: Add info
Old 07-14-2019, 03:15 PM
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Also, if you can swing it, replace the hard/flex line from the master to the slave. The rubber portion is now 36 years old. You're losing pressure from the rubber hose expanding when you press the clutch pedal. It might not be much expansion, but it does make a noticeable difference. Same with brake lines.

I replaced master, cylinder, blue hose and hard/flex line when I had the engine out. The clutch feel and control is much, much better. Feels like a new car.
Old 07-16-2019, 10:23 AM
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My observation of that video is that the shaft that goes into the MC from the clutch arm is adjusted too short. Here's why.

The clutch pedal has a "camming" or over-center effect on its pivot and the spring that returns the clutch pedal. The clutch pressure plate and its return springs also have a return pressure on the clutch pedal but that's just linear and has no over-center function.

So as you're pressing the clutch pedal down, you're supposed to start compressing the pressure plate return springs before you reach the pedal's over-center point. That's so when you release foot pressure on the pedal, the clutch pressure plate return springs will push the pedal back up over that over-center point and then the clutch pedal's spring will finish returning the clutch pedal up high where it's supposed to rest.

So in the video, he needs to elongate the shaft with the 13mm nut by loosening it and spinning the shaft so its longer. That will in turn cause the clutch pedal travel downward to hit those pressure plate springs earlier in the pedal's travel. Edit to add: His shaft is so short that the pressure plate springs run out of travel in pushing the pedal back up, BEFORE the pedal mechanism has reached that over-center point. Hopefully you can see from a geometry standpoint that if the shaft were longer, the pedal would be pushed higher by the pressure plate springs.

If you have that exact issue, try adjusting it. If your issue does not appear 100% of the time then its likely you have air in the line as you suspect because variations are caused by the air in the line expanding as the car's engine bay and firewall heat up. I recently went through my clutch system and found the PO also had clutch issues for years. I resolved them and my thread is here on the first couple pages because I just finally resolved it a month ago or so. Maybe 3 months ago? Further, I discovered some inconsistencies with Porsche's clutch adjustment instructions and some forum thoughts in the process that may be useful to read.
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Last edited by IdahoDoug; 07-17-2019 at 10:40 AM..
Old 07-17-2019, 10:27 AM
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Quote:
Originally Posted by pdxfj View Post
Also, if you can swing it, replace the hard/flex line from the master to the slave. The rubber portion is now 36 years old. You're losing pressure from the rubber hose expanding when you press the clutch pedal. It might not be much expansion, but it does make a noticeable difference. Same with brake lines.

I replaced master, cylinder, blue hose and hard/flex line when I had the engine out. The clutch feel and control is much, much better. Feels like a new car.
That is some good advice. I will have to look through my records to see if I have (or haven't) replaced this somewhere over the past decade. 😁
I'm happy to hear you have your Porsche clutch system feeling like new.
Thanks!

Last edited by SpidrVII; 07-17-2019 at 10:40 AM..
Old 07-17-2019, 10:35 AM
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IdahoDoug
My Porsche's clutch pedal condition is exactly like the one in the video.
I will most definitely follow your instructions to (hopefully) resolve the issue.
I will also check out your other thread.
Thank you!

Last edited by SpidrVII; 07-17-2019 at 11:50 AM..
Old 07-17-2019, 10:39 AM
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