Sudden weird clutch pedal feel

[kp278]

Hi all

Driving the car today and it suddenly feels like the clutch pedal travel is split into two movements - the lower half pushing the fluid, and the upper half is just a spring action.
It doesn't stick at this halfway point.
It's easy to drive the car using just the lower half of clutch pedal action if I keep my foot resting on it.
If I remove my foot then the clutch springs up fully no problem.
Pulling away and changing gear is fine.
Clutch is not heavy.
Biting point is just before the halfway point.
It was fine last night.
I bled my brakes last week but not the clutch.

I found this interesting: http://911uk.com/viewtopic.php?t=148455

Interested in any other thoughts.

Thanks!

 

[kp278]

Question: How does the piston/booster spring work?

I see it working, in first half of depress it just pivots and in second half the spring expands towards its resting state. It's at this cross-over point of pivot/expand that I feel this difference in the clutch pedal, where it's seemingly a lot weaker than it was

 

[Alex]

Those springs are a pain. I had one on a CLK. It snapped and fell off - clutch was great after that. It's a much a bug bear as overservo'd brakes.

 

[kp278]

I'll try the basic stuff first...
Lube the pivot points (although I did a bit of this 2 weeks ago);
Then remove the spring;
Then bleed the clutch;

It's in with an indie for geometry setup next Tuesday so I'll get their thoughts

 

[spinnaker]

Just FYI I *think* you are supposed to use a sturdy nail or similar to lock the spring in the compressed state before removing it.

 

[kp278]

Ok so clutch is now sticking at the halfway point. I lubed it and it seemed to help for a few seconds but started sticking again. I removed the piston and the clutch pedal flops a bit, it's quite loose on the first half of the press and then operates as normal on the lower half, albeit harder as expected. Effectively I have half the pedal travel

 

[chowgar]

I'll save you going down a rabit hole of trying many things, like I did until I found the real issue. I had exactly the same issue as you very recently. I started with bleeding the clutch and this only remedied the issue for around 5 weeks.

In the end, it was either the clutch master cylinder or slave cylinder that was at fault. It was most likely the clutch master cylinder, but I couldn't be certain as I had both changed out.

Clutch is working perfectly again. Oh and just so that you're aware, the clutch booster spring only helps you to depress the clutch.

 

[kp278]

Yes I read your thread with great interest as it sounds identical. Can I ask what you paid for the work? I think I read you sourced the parts from autodoc?

The booster spring definitely helps with the upwards motion of the pedal - once you're passed the sticking point it acts like a fulcrum and forces the pedal upwards. If you take the piston out - no force and the pedal doesn't return to it's starting position.

 

[chowgar]

I paid around £300 labour to have the clutch master and slave cylinders replaced, which included bleeding the system too. The parts cost me £250 from Autodoc, with another £30 for brake fluid. I would try to get the parts from here in the UK though, as I had a faulty slave cylinder which I had to return and it took a couple of weeks to get refunded. This was a warranty claim, as the part failed after being mounted to the vehicle. It was straight forward to make the claim and surprsingly, they even refunded me £170 for labour charges that I incurred!

 

[kp278]

Thanks. So I checked the old paperwork that came with the car and the slave cylinder was changed last year, albeit with a part cost of £85+VAT so not OEM. It's with the indie now for geometry stuff and I mentioned the clutch issue, he said he would only fit genuine slave cylinder. I've read Sachs are ok but some other manufacturers not so much. I think if slave is newish then perhaps the master needs doing. Will see what the indie thinks after he's had a poke.

I put the spring back in last night and it's working as it was a couple of weeks ago, but I think my cars 'normal" is still not normal, still not much happens through the first half press of the pedal. Here it is with the spring removed: https://youtube.com/shorts/efZNuAQNIXM?feature=share

 

[spinnaker]

I'm in a very similar position to you with what feels like a dodgy clutch issue. I don't tend to get a consistent clutch response which makes me worry that I can't rely on it.

My car's clutch slave cylinder was replaced with a Sachs one last year too while with the previous owner. In the next couple of days I am getting a local indie to replace the master cylinder as suggested by chowgar. I'll report back on how that goes. Fingers crossed.

Interesting that your indie advised against Sachs slave cylinders over OEM. I noticed recently that if you look at the genuine Porsche part on Design911 and zoom in on the photo you can see the Sachs logo on the genuine Porsche part. The image is a different one to the one they use for the Sachs part so I think it is unlikely they have used a photo of the Sachs one in place of an actual Porsche one.

https://www.design911shop.com/Porsche-996-997-Clutch-Slave-Cylinder-99711623704-6283000043/prod6083/

 

[kp278]

Be sure to let us know how it goes. I think if they recommended I fit a £250 Porsche part over a £100 sachs part I'll be asking the question. I think he did say 'OEM" so he could well mean whomever makes the OEM part.

 

[chowgar]

Both of my Clutch cylinders recently fitted are Sachs. I've fitted countless of their parts in the past and they are a very large reputable company. You probably don't realise it but, your clutch and fly wheel are probably made by Sachs, as this is one of their most common parts.

The mostly likely culprit in these cases as confirmed by my specialist and previous advice given by our forum guru Demort, is the clutch master cylinder.

Once you've fitted it, you will be pleasantly surprised at how much better the clutch feels. It even restored my low biting point to a little higher up.

 

[spinnaker]

Thanks chowgar, I really hope so. Will check back in here after it is done.

 

[kp278]

Interesting, the indie said the biting point was a little low. He did also say he hasn't had to change a Porsche master cylinder for about 12 years and it's nearly always the slave. It's going back in a months time to investigate further.