FRporscheman

On my mom's 968, the clutch pedal engagement point has always been very low to the floor. I figured too many, or too few, shims were used on the release bearing / pressure plate during the last clutch job. I tried adjusting the clutch pedal where it connects to the clutch master cylinder but it wouldn't let me adjust it enough. Not even close to enough.

I took out the clutch today to see what's going on. Apparently clutch kits come with 2 shims. I found both shims installed, and they were put on the back of the pressure plate. I figure these shims could be left out, or even put on the front side of the pressure plate. I know these shims are used to offset the engagement point of the clutch (right?), so I wanted to know others' experiences with this. I really want to get this right!

TIA

Jaap968

When I recently replaced the clutch and pressure plate I was also not sure how many and where to put the shims. Because the old clutch had two (installed on the gearbox side of the pressure plate, between the bearing and spring like ring) I just installed two again, which took some effort. My clutch also engages close to the floor. However I don't think the shims are there to change the engagement point but just to have the right tension between the bearing and pressure plate (according to clark garage you should install as many shims so that the bearing still can be shifted when using a little force). IMO they are too thin to make any difference in engagement point. The engagement point is probably just defined by the construction and due to the hydraulics is adjusted automatically? Sorry not to much help.

Jaap

FRporscheman

In my red 968 the engagement point is exactly halfway down. I know the shim location affects the engagement point, and it does make a bit of a difference. Say the PP moves 1cm (10mm). Then assume the clutch pedal moves 30cm (300mm). Then assume each shim is 1mm. That means the shim offsets the PP action by 10%, which I believe translates to 3cm of pedal action. This is how I always thought of it, anyway, so please correct me if you know more than me.

Jaap968

Hi Arash,

Because of the low engagement point on my car I also tried to understand the function of the shims.
My assumption is that (using your numbers) if the PP needs to move 10mm to release the clutch plate, and this requires the pedal to move 30cm, this would remain the same regardless of the shim location. Once you install the TOB on the PP (with shims on front or back) this will be the starting position and the clutch pedal is forced all the way up by the spring, then the hydraulic system will remove all play and it will require the same amount of pedal travel to release/engage. If the clutch was cable operated then the shim location would affect the engagement point as long as you would not adjust the cable length. Does this make sense?

Jaap

FRporscheman

Hey Jaap, it does make sense. I overgeneralized in my little explanation though. Sure, not all 30cm of pedal travel is used to work the PP. Also, once the pedal reaches the bite point, the distance of travel is the same regardless of shims or anything, because it is working the PP.

The shims can change the location of the TOB, which would offset the fork a little, and that would change the amount of hydraulic travel needed to cause release, which would affect how far you have to push the pedal until it finally releases.

968workaholic

It sounds to me that there is just air in your system, despite your attempts to bleed it out. Are you using a pressure bleeder, or just manual bleeding?

FRporscheman

The system was bled by the dealer when the clutch hose was replaced (before we bought it, 10k miles ago I think).

968workaholic

I would try bleeding the system to see if that helps. Use a Pressure Bleeder for best results. Motive Products makes a nice system.

FRporscheman

Update: I got the car reassembled with the freshly sanded FW/PP, and some fresh grease where needed. Oh, and a new rear main seal which was a PITA. The pedal now feels very wrong... and it won't come up all the way. The TOB stayed on the PP and I didn't touch the shims so I don't know what's up. I will try adjusting it and re-bleeding it tomorrow. I have a Motive Power Bleeder.

Incidentally, while reassembling I realized one can see the shims from the clutch inspection hole. I decided to check my red 968 which has perfect pedal behavior, and it has both shims on the rear side just like the blue car. I guess this means my whole theory about shims and relocating them can be disregarded. It may all be true but since my red car feels good, blue car feels bad, and both have the same shim config, I say the shims aren't part of the pedal tuning process. I'll see if tomorrow's efforts make the pedal work any better.

968workaholic

Sometimes you have to bleed the clutch quite a few times to get all of the air out. It helps to drive the car for a day, then try to bleed it the next. Eventually it will feel like your other car. The clutch hydraulics just like to be stubborn sometimes.

FRporscheman

OK update. It was never the shims.

I since have been able to improve the clutch feel with more bleeding. In total, I spent an hour bleeding manually (2-man) and an hour using the power bleeder. The power bleeder made it worse so I did the manual method again and now the pedal is about 30% better than how it was initially. The clutch hose and both cylinders are relatively new (replaced at dealer, by PO). Yes, I am using fresh fluid.

All this bleeding, with different methods, and still the clutch sucks. What am I doing wrong? Can someone please spell out the proper bleeding procedure, maybe I'm overlooking/neglecting a simple step or rule?

Why do all 12776 968s have a clutch that behaves differently?

968workaholic

When you say the clutch sucks, does the pedal not come up all of the way or does it engage low/ have a spongy feel?

RajDatta

How are you pressurizing the system when bleeding?
Raj

AllenM

Instead of asking you what you are doing wrong, I'll tell you what worked for me.
I replaced the master, slave, and clutch hose all at the same time and bled the brakes as follows.

Jack up the rear of the car only, leaving the front end on the ground (important step).
Make sure your reservoir is topped off at all times during this process.
Attach and pressurize the motive.
If the clutch pedal doesn't spring back, leave it pressed to the floor.
Crawl under and start bleeding. don't bleed too much or the reservoir will run out and the motive will start putting air IN the system.
Pull the pedal up and bleed a little more.
After this my pedal worked but felt soft so I went the manual route.

When manually bleeding, follow these steps:
push pedal, open valve, close valve, release pedal.
After two-three times, my clutch was back to normal.
Make sure your friend isn't releasing the pedal while the valve is open and make sure he isn't constantly pumping the pedal either causing bubbles.

Hope this helps. It took me a while to get it all right. At first I had the car level and kept running out of fluid in the reservoir. There is surprisingly little fluid in the lines, so you don't have to let out a whole lot of fluid each time you open the valve.

RajDatta

When using the motive bleeder, you should have plenty spare in the bleeder tank to support any additional fluid needs. Not sure why one would run out of fluid?
This is why I asked how the process was done.
Allen, I have tried your method as well. Its a 2 person job. Besides that, it does work.
Raj