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I've replaced master and slave cylinders on a 2k 986. I've bled the system four different times following the procedures in the video below and using the procedure outlined in the common renntech link. (see also below)
The symptoms I have are that at about the top 10-20% of the pedal's travel I can feel the spring "pop" the pedal up to its highest point. And when I depress the pedal to start the car, I have to press the clutch really hard. (to toggle the switch I presume). I'm about at my wit's end with this. Does anyone know what I could be possibly be doing wrong? I'm using a Motive bleeder, Dot4, and Sachs parts. But still this issue persists. Worse yet, I am on my second replacement slave, because the first one failed catastrophically after about a week of use. When it was installed, it too had the same issue, I had to press very hard to get the car to start and at the top of the pedal's travel it feels springy. It was while parked at a gas station starting the car that the part failed, just as I pressed down hard on the clutch to start the car. POP! I must be doing something wrong, but what? Any ideas for me Porsche friends?
Doesn't sound like it has anything to do with the bleed.
The issue with needing to press the clutch really hard has to do with a failing clutch switch. If you put your head underneath the dash you can see the switch. There are actually two switches. One detects whether the clutch is completely released and is a plunger type switch identical in shape and position to a similar switch on the brake pedal. The switch I am talking about is the other switch in the clutch pedal assembly. It is engaged when you fully depress the pedal. It has a metal actuator that you can bend a bit to see if you can get it to engage earlier, but I suspect it has broken and the switch needs replacement. A PITA but not a difficult task.
The other thing you are noticing is the action of the clutch assist spring. It serves to help with the force to depress the club and also holds the pedal to the full up position. Normally you wouldn't notice its action, so maybe it is broken..I do suspect you are just feeling its proper action.
Here is an image of the parts I talked about in my last post. The clutch assist spring is #9 and the clutch switch that is causing you trouble is #16.
Don't panic when you do't see the cotter pin in the post of the spring. It gets removed after installation and keeps the spring compressed to easy the installation process.
I very much appreciate the input Anker, but I'm a little worried that tacking on two more problems (the clutch pedal switch and spring) takes me away from what I suspect the real issue here is. The way I got to this point was having a clutch pedal on the floor: failed slave cylinder. And indeed when I bleed the system and slowly move my pedal by hand I can hear the switch engage just fine. It's not until it's bled that it suddenly becomes very hard to push it in far enough to hit that switch.
And on the upswing of the pedal, it definitely feels like the spring is working (I've watched spring when I installed a new master cylinder at the same time), but it doesn't feel at all like the clutch pedal is operating as normal, hydraulically-speaking. I drove it for four years before this with no problems, so I think I know (but I definitely could be wrong) what "normal" operation is. The pedal feels funky on the top 20% or so of the uptravel as I shift. And feels even funkier/slow/laggy when I stop the car and part it. The pedal comes back up very slowly. I would think a failed spring would feel the same sort of wrong in both situations.
In any event, your comments got me to reading about the switch and how you can defeat (for me, if only temporarily) so I can start the car without Hulk-legging the clutch. Thanks much!
I very much appreciate the input Anker, but I'm a little worried that tacking on two more problems (the clutch pedal switch and spring) takes me away from what I suspect the real issue here is. The way I got to this point was having a clutch pedal on the floor: failed slave cylinder. And indeed when I bleed the system and slowly move my pedal by hand I can hear the switch engage just fine. It's not until it's bled that it suddenly becomes very hard to push it in far enough to hit that switch.
And on the upswing of the pedal, it definitely feels like the spring is working (I've watched spring when I installed a new master cylinder at the same time), but it doesn't feel at all like the clutch pedal is operating as normal, hydraulically-speaking. I drove it for four years before this with no problems, so I think I know (but I definitely could be wrong) what "normal" operation is. The pedal feels funky on the top 20% or so of the uptravel as I shift. And feels even funkier/slow/laggy when I stop the car and part it. The pedal comes back up very slowly. I would think a failed spring would feel the same sort of wrong in both situations.
In any event, your comments got me to reading about the switch and how you can defeat (for me, if only temporarily) so I can start the car without Hulk-legging the clutch. Thanks much!
Have you used Porsche Diagnostic equipment to open ABS valves to fully bleed system ? I believe that's what you need to do. I think a durametric can do this too.
You shouldn't need to do anything with the brakes or ABS to bleed the clutch.
I am wondering though if your catastrophic failure of your previous slave and your current problem are related.
Are you sure you have the correct slave for your car? There were a couple of different types for the early boxsters I recall. I would suppose an incorrect one could have insufficient travel, resulting in the failure you described.
You shouldn't need to do anything with the brakes or ABS to bleed the clutch.
I am wondering though if your catastrophic failure of your previous slave and your current problem are related.
Are you sure you have the correct slave for your car? There were a couple of different types for the early boxsters I recall. I would suppose an incorrect one could have insufficient travel, resulting in the failure you described.
That's an interesting notion CBR944. As far as I know I have the correct slave. I ordered from Pelican it looks like the same Sachs (just different color rubber… old black, new white), but I'll double check. The slave installation has me concerned too. Is it possible to not install it correctly such that the rubber boot binds inside the hole or something?
Another thought - I recall reports of difficulty engaging the clutch being due to clutch failure (not sure if the disc or the t/o bearing). Obviously not a simple job to check and fix though...
04-04-2018, 02:03 AM
986 Master Slave Bleed problems
