pauljosef

I first wrote this in response to a thread that talked about "bucking" but now realize it is a different issue. I am a complete rookie and just joined Rennlist. I t have a clutch issue which I don't understand. 2006 Carrera S (purchased certified pre-owned at 21k miles, now at 35k). About a month ago I accelerated from a standstill in Sport Mode and the clutch slipped(!) The engine RPM's raced ahead of my vehicle speed. I immediately stopped and took off again more slowly with no apparent problem except the unmistakable smell of burned clutch facing filling the cabin. I had no further problem and no apparent change in the "feel" of the clutch operation. Had 2 experienced Porsche technicians check it out and they say no problem. I put it off to the sport mode increased throttle response getting ahead of me. Now it has happened again. This time it felt like the clutch pedal just didn't come up all the way.
The clutch never slips under load in any gear. When I first bought the car, I thought the gearbox felt a little balky but was told this was typical of 911. I have driven a friend's 06 C4S and his shifted much more smoothly. The Boxster's I have driven are silky smooth. I am wondering if I have a problem in the hydraulics or the "throw-out bearing"(?) such that the clutch is not consistently and completely engaging and disengaging. Please share your experience and advice.

Edgy01

I'm surprised that two Porsche techs didn't feel a problem. These cars should be smooth throughout the acceleration process. When you first accelerated from zero did you intentionally slip the clutch to get it going, or did you fully release the clutch before you hammered the throttle? I absolutely never accelerate my 06 unless the clutch pedal is fully released--otherwise you are burning clutch material.

As an S model, they are supposed to have self-adjusting clutches.

equiraptor

I don't think you have a problem. A number of modern Porsches I've driven have exhibited this behavior if I launch aggressively with some clutch slip. It first happened to me in a 986, and has since happened in a 987 and a few 997s. I never played with any of the cars enough to isolate exactly how to consistently reproduce the behavior, but it never led to a problem, either. It only happens if I rev the car over 4,000 rpm and then release the clutch fairly quickly, but still with some slippage, trying to get the rear tires to be right at their limit of adhesion.

Try either following Dan's advice and not burning up your clutch, or using a more gradual release of the clutch, or turning off traction control (off, not sport mode).

Edgy01

From what I understand with the more modern cars, if you are very smooth with your footwork, you can just about release the clutch fully without even giving the car any gas because the engine management computer feels the drag on the engine and compensates by adding a little rpm on its own. ONLY after the car is in gear, with the clutch petal all the way up and your foot off it should you then proceed to mash the throttle. Quite often I have my foot off the clutch pedal fully when I'm going about 2 mph. Then, and only then, do I proceed to thrash it! I have routinely gone well over 100,000 miles on clutches in my 911s.

pauljosef

Thanks for the input (and the reassurance). Each time, the car was at operating temperature (Texas summer heat). I had been driving in Sport Mode, pulled to the side of a highway to get something out of the back, and took off in Sport Mode as fast as I could because I was getting back to highway speed from the standing lane.The 1st time, I have no trouble believing that the enhanced throttle response got away from me in that I slipped the clutch slightly (as normal) to start. I have pampered this clutch from the beginning because I didn't know if the 1st owner was learning a manual transmission and had thus caused a lot of clutch wear. I blip the throttle a little, let the clutch out all the way and then accelerate with the clutch fully engaged. Maybe the Sport Mode accelerated it too fast. But the second time, it seemed that the clutch just didn't come out all the way. Is it possible for a clutch to intermittently not fully engage or disengage? It seems to be a healthy clutch in that it shows zero signs of slipping under load. Sometimes when I go to shift into 1st from 2nd (at say 10 mph) it is balky and I can hear (and reproduce) a heavy thudding sound, seeming like the clutch is not fully disengaged. But it doesn't do that always. Can some hydraulic or mechanical component act to make a clutch not work properly SOMEtimes? I love this car and have put some additional money into it(Sport Exhaust and K40).

utkinpol

when you deal with dealer - let them record this complaint, and state not 'slippage' - state that your clutch pedal got 'stuck' and did not return back - if that has happened for real. be quite specific in what has happened.

with second complaint it should warrant them to take clutch apart and investigate and you should not pay for labor. discuss more with service manager. it may be faulty pressure plate or something else, do not tell them what do you think is wrong - just say 'clutch pedal did not return back when i released it'

Macster

You sure the tires weren't spinning under hard acceleration? The sides of highways are covered/littered with all sorts of slippery stuff: gravel, sand, dust, nails and all sorts of debris that traffic tends to cause to migrate out of the traffic lanes.

(I seldom venture onto the side of any highway or freeway with my car for fear of getting a tire punctured. I almost always wait and take an exit and pull into a gas station or other business's parking lot, though large parking lots can have sharp pointy things too cause businesses are cutting back on having their lots cleaned. And when taking off I do so very gently so if there are any sharp things under the tires they don't get jammed into the spinning tire or kicked up by the front tire to then get picked up by the rear tire.)

If at say 3K rpm in 4th gear and you floor the throttle -- on a good smooth road with good traction -- and the clutch doesn't slip then I suspect the problem if it is clutch slippage when taking off agressively is something in the clutch hardware is preventing the full release and engagement of the clutch.

The disc made be binding/dragging on the input shaft splines of the transmission of the clutch slave piston is binding in the cylinder.

Of course, you want to eliminate what you can of the hardware outside of the transmission bellhousing in case it is something that can be fixed without having to drop the transmssion.

Sincerely,

Macster.

equiraptor

I'm not sure you need any modern, fancy engine management for this. I've been able to get the car moving in this way in every car I've tried it with. This includes cars like the '84 Camry on which I learned to drive (yes, a manual) and an '84 Ford Tempo. It's not a trick of the engine management so much as a flywheel combined with a properly functioning idle setting. In cars with lighter flywheels, a more delicate touch on the clutch is needed. It's very, very challenging to do this in my Miata, which has an extremely lightweight (for the street) aftermarket flywheel.

This is the correct behavior for preserving the clutch. This is not the correct behavior for a quick launch. If you want the best launch the car can do, rev it up and slip the clutch, keeping the tires at (but not past) the limit of adhesion. This does wear the clutch, however, clutches are wearing parts. There isn't anything "wrong" about this method, so long as the driver and the owner of the vehicle are fine with the added clutch wear.

utkinpol

No. you do not let clutch 'slip' for drag racing start.

you depress clutch fully, engage first gear, then start depressing clutch very slowly with minor rpms until you feel clutch starts to engage, then you depress it for hair thin again so it would disengage but keep your foot in that position making sure car does not roll, increase RPMs to 6K, then when lights do change you just drop the clutch - means quickly remove your foot altogether simultaneously giving full throttle.

rear axle should 'hop' at such start as rear tires on 911 never slip , you do punish your gearbox a lot, may even get a tooth broken off from first gear but you do not slip your clutch disk.

if you 'ride' the clutch disk gets slipped at such forces - it gets overheated and becomes overly slippery and you essentially loose any clutch for a while until it cools down.

equiraptor

Wheel hop is slow. Tire slip is faster, but still not as fast as the tires gripping. The fastest launches we measured, no matter the car, meant slipping the clutch and keeping the tires at the limit of adhesion.

This does not involve "riding" the clutch. There's a difference between less than a second of slip and riding the clutch. Yes, the behavior I describe would overheat the clutch if repeated in quick succession, but at least in the racing I've done, it isn't. Clutch overheating isn't a problem with this launch method, and it produces quicker times than allowing wheel hop.

pauljosef

I am confident that the wheels were not spinning because I had no traction control light and---I know what that feels like and this was clearly clutch slippage, confirmed by the unmistakable aroma. However, all of this input tells me that, if there is a mechanical or hydraulic defect, it will happen again and, because I am now alert to it, I will recognize it. If it was caused by my" too-rapid" accelerating with the clutch not fully engaged, that won't happen again. I've never been one to "pop" the clutch or drag race for that matter. This was driver error or mechanical defect. So I will report what happens.

I am very grateful for all of this input from more experienced Porsche drivers and a forum in which to receive it. Glad that I bought a 2 year membership and wish I had done so in May.

solidst8

I've had this happen a couple times before. Also both times when under sport mode, and the clutch pedal did not come back up all the way. Smelled clutch burning. Didn't think too much of it at the time. I bought the car with 40k miles on it so I assumed previous owner didn't know how to preserve a clutch. The car still drives fine and even in spirited driving, the clutch does not appear to slip at all.

But now you've got me thinking, I've had clutches go bad on other cars and never did the clutch pedal ever get stuck midway. Keep us posted on what you find out.

yemenmocha

I've experienced this only once as the OP described and it was sport mode. It was also after I had not driven my car in awhile and instead had driven a differnt 6MT. I suspect that once the OP is more acquainted with the car it should happen less often if not at all. Anyone else agree?

ADias

This has nothing to do w/ SC Sport mode. If the clutch slips on of 3 things happened: (i) you did not release it completely or (ii) there's something wrong w/ the master cylinder hydraulics, or (iii) the clutch is worn.

You know if it is (i) or (iii). If the issue only happened once it could be (ii) hydraulics. Have it checked. Have you flushed the brake lines every 2 years or more often if you track the car?

pauljosef

I originally raised this issue with great response and information. The only way sport mode has anything to do with it is if the increased throttle response causes the RPM's to be too high when you release the clutch for it to engage. Its not that the sport mode changes the clutch in any way. It hasn't happened to me again but I will be alert to the factors involved if it does.

More rookie questions: where is the cabin filter located on my 06 Carrera S?