There's no way my dealer will ever find this, but it happened again today:
1) Start car
2) Back out of garage
3) Drive down hill to cross street
4) Turn left on cross street, get up to speed
OK, things are great so far. No clutch issues, no shifting issues.
Roll up to slowing traffic, hold clutch in.
About five seconds later, traffic starts moving, put shifter into second, and release the clutch.
I apply gas, everything seems normal, but after 1/2 to 1 second I feel a strong abrupt "thunk" from below and behind me as if the clutch had (unknown to me) been slipping slightly and it just hooked up fully. A good example is it's what you feel if you hit a small patch of black ice just as you pull away from a stop - it slips and you get a thunk when your tires hit regular pavement again.
So:
1) This happens only
once
, when it's cold.
2) I can't make this happen at will. (See (1).)
3) Even if I "drop" the clutch pedal, I don't feel the same kind of "lurch" - it's nowhere near as abrupt.
Anyone else? I would imagine if it were a clutch slave cylinder or anything similar it would happen more than
just once
.
I think the only thing I can do is mention it to my dealer so if I find I need a new clutch at 6,000 miles there's a note indicating I felt something was wrong.
No ideas but if the clutch were slipping enough to make a thunk when it locked up I'd expect that your revs wouldn't match the speed. And if accelerated that revs would rise faster then speed for that gear. Sort of like a loose torque converter.
Is there any chance there's something loose in the motor mounts etc? I'd mention it to your dealer but wouldn't expect much if like mine.
I get this exact same problem when its cold, not sure if its the clutch or not.
BillK, did you read the thread back in August regarding the clutch delay switch? Sounds like there may be some connection.
I did, but it seems strange that it only does it once, and then only when cold.
Perhaps there's a bad batch of switches…
Update:
It still feels like the clutch, but I watched the tach like a hawk today when it did it and the tach did not flutter at all; if it were really the clutch slipping and catching I would think I would have seen the needle abruptly rise and/or fall rather than a nice smooth increase in RPMs as I accelerated.
OK, so I've been playing with it a bit more, and it always seems to happen right around 1500 RPM when accelerating and seemingly only in second gear.
:helpme:
If you are Starting from Stationary........
Why are you Starting off in Second Gear? - Could this be the Problem?
Try First Gear.............!
The usual way this happens is:
1) Turn onto street
2) Accelerate, note traffic ahead is slowing, press clutch and hold down
3) Brake
4) Traffic ahead starts to move. Speed is now 7-8 MPH, so shift into second gear, release clutch fully and start accelerating.
5) Note "glitch" as tach passes 1500 RPM; at this time the clutch pedal has been completely released for 1/2 to 1 second.
This doesn't sound like a clutch issue. It sounds like a dual mass flywheel issue, actually not an issue, and it's not that uncommon. People have been reporting this kind or 'weirdness' on all sorts of cars since dual mass flywheels started going into them, and I've experienced it in mine too.
Understanding the Dual Mass Flywheel:
The flywheel is a necessary and important component of any internal combustion engine. It adds mass to the crankshaft, mass that is needed to smooth out the power pulses and to provide enough inertia to propel the next piston through it's compression stroke.
Even with a flywheel, the output of an internal combustion engine is not totally smooth. There is a lot of wow and flutter. In other words, every time a cylinder fires off it causes a momentary acceleration followed by a deceleration, there are many peaks and dips in the rotation rate of the crankshaft. In the old days, manufacturers placed springs in the clutch disc to absorb some of these pulses so the gears in the transmission would not chatter and make noises. This worked OK, but it added complexity and mass to the clutch disc. That extra mass made the disc heavier, which caused the syncros to work harder and made the syncro mesh transmission shift slower.
The dual mass flywheel was created to take over this responsibility so the clutch disc could be simplified and lightened. By moving the dampening functions to the DMF, more sophistication can be added than could be used on a clutch disc because more mass can be added to a flywheel. A DMF not only contains springs like the older clutch discs, it also contains hydraulic dampers.
These longer springs and dampers connect two smaller flywheels together, which by design splits the flywheel so there is one for the engine, one for the transmission. By design there can be more movement between these two flywheels than could be achieved by putting springs in a clutch disc. The springs can be softer because of the dampers. When this system is cold, the dampers don't allow much movement. Then as they warm up, the movement loosens up. This is likely what you're feeling. Your DMF breaking loose and moving against it's dampers. It feels like the clutch slipped, but it didn't. The DMF did, but only by a few degrees which is why you can't see anything on your tachometer.
So, now you know. The next time you feel this, reflect on this thread and you'll likely say to yourself, "Damn, that guy was right. It's nothing to worry about. What kind of freak knows that much about cars....?"
OK, maybe, hopefully you'll leave that last part out....
Really!!!!
What
kind of freak????
Is the DMF new to the Cayman S?
I ask as I never felt this in the five+ years I owned a 986 Boxster S…
The 986 Boxsters DID have a dual mass flywheel, but I am sure it was a different flywheel with different damping and spring rates. The different gear ratios of the transmission will also make it feel different.
What if the "thunk" you feel is actually an abrupt change in engine power due to a malfunction in the sensor/computer/injector/variocam/ignition timing/foot throttle/throttle body complex? Just another of my long shots but I would want to know if the mechanics checked for error codes or just drove the car and, say looked at the engine mounts. The "second gear only" business is puzzling. Have you really tried to duplicate the problem in other gears at the same rpm? Hope its not a transmission defect.
I haven't felt it in other gears.
No codes, "cannot reproduce" on the service invoice, natch.
